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American-Airlines-Flug 96

2010-05-04T02:36:06Z

EditorASC: Re-wrote first paragraph to correct erroneous information

{{Infobox Airliner accident
|Name = American Airlines Flight 96
|Crash image = Aaflight96dc10.png|360px
|Image caption = Artist's depiction of American Airlines Flight 96 losing its aft bulk cargo door
|Date = 12 June 1972|
|Type = Design flaw, Cargo door failure, control failure
|occurrence_type= Accident
|Site = [[Windsor, Ontario]]
|Origin = [[Los Angeles International Airport]]
|Destination = [[LaGuardia Airport]]
|Stopover = [[Detroit Metropolitan Wayne County Airport]]
|Last stopover = [[Buffalo Niagara International Airport]]
|Fatalities = 0
|Injuries = Several minor injuries
|Aircraft Type = [[McDonnell Douglas DC-10|McDonnell Douglas DC-10-10]]
|Operator = [[American Airlines]]
|tail_number = [http://aviation-safety.net/database/record.php?id=19720612-0 N103AA]
|Passengers = 56
|Crew = 11
|Survivors = 67 (All)
}}
'''American Airlines Flight 96''' was a regular [[McDonnell Douglas]] [[DC-10-10]] flight operated by [[American Airlines]]. The flight suffered a cargo door failure on 12 June 1972 while flying over [[Windsor, Ontario]]; it is thus sometimes referred to as the "Windsor incident."<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref>

The rapid [[Uncontrolled decompression|decompression]] in the cargo hold caused a partial collapse of the passenger compartment floor, which in turn jammed or restricted some of the control cables which led to various flight control hydraulic actuators. The jamming of the rudder control cable caused the rudder to deflect to its maximum right position. The cable controls to the number two (tail) engine were severed, causing that engine to shut down.<ref name="NTSB">{{cite web
| title = Aircraft Accident Report: American Airlines, Inc. McDonnell Douglas DC-10-10, N103AA. Near Windsor, Ontario, Canada. 12 June 1972.
| publisher = [[National Transportation Safety Board]]
| date = 1973-02-28
| url = http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf
| format = PDF
| accessdate = 2009-03-22 }}
</ref> Fortunately, there was no rupture of any hydraulic system, so the pilots still had control of the ailerons, the right elevator and the horizontal stabilizer. However, because the right elevator cable was partially restricted, both pilots had to apply back pressure on the yoke for the landing flare. Additionally, the approach and landing had to be made at high speed, to prevent the sink rate from becoming too high. The tendency to turn right was offset by using 45 degrees of left aileron, combined with asymmetrical thrust of the two wing engines. In spite of the partial restriction of the controls, the pilots were able to make a safe landing at [[Detroit Metropolitan Wayne County Airport]] with no major injuries.

The cause was later traced to the door latching system, which had failed to close completely. A separate locking system was supposed to ensure this could not happen, but proved to be inadequate. McDonnell Douglas instituted a number of minor changes to the system to avoid a repeat, but two years later [[Turkish Airlines Flight 981]]'s rear cargo door failed for exactly the same reason, causing the aircraft to lose all control and crash outside [[Paris]] with a loss of 346 passengers and crew, the deadliest air disaster to that point.

==Accident details==
Flight 96 was a regularly scheduled flight from Los Angeles to [[LaGuardia Airport]] with stops in [[Detroit Metropolitan Wayne County Airport]] and [[Buffalo Niagara International Airport]]. On 12 June it was being flown by DC-10-10 N103AA. It left Los Angeles 46 minutes after its scheduled 1:30 pm departure due to passenger loading and traffic, arriving in Detroit at 6:36 pm. At Detroit the majority of the passengers disembarked, and the plane took on new passengers and cargo. Leaving Detroit the aircraft had 56 passengers and 11 crew. The flight departed at 7:20 pm, climbing to 6,000 for a hold before capturing V-554 (a [[victor airway]]), then climb to flight level 210 (21,000 ft).{{Citation needed|date=January 2010}}

At 7:25 pm while climbing through 11,750 ft, the crew heard a distinct "thud" and dirt in the cockpit flew up into their faces. Captain Bryce McCormick reported that he momentarily believed they had suffered a mid-air collision and the cockpit windows had been smashed. At the same time, the rudder pedals moved to their full-left position and the engine controls moved to idle. McCormick immediately took manual control of the aircraft, and attempted to re-apply power, finding that engines 1 and 3 would respond normally, but engine 2, in the tail, would not allow its controls to be moved. McCormick was able to level off and stabilize the speed at 250 knots, although at this speed control was very sluggish. They declared an emergency and requested routing back to Detroit.{{Citation needed|date=January 2010}}

In the cabin, the flight attendants saw a "fog" form within the cabin and immediately recognized it as a depressurization. Two crew were in the rear lounge area, and the floor under their feet partially collapsed into the cargo hold, giving them both minor injuries. In spite of this, the cabin crew immediately attempted to ensure the oxygen masks had deployed properly, but having occurred below the 14,000 ft limit, the masks had not deployed. One of the attendants obtained a walk-around oxygen bottle and called the cockpit on the intercom to inform them that the damage was in the rear of the aircraft. On instructions from the cabin, the attendants instructed the passengers on emergency landing procedures. A number of passengers later reported that the aircraft safety cards proved useful in locating the nearest exit.{{Citation needed|date=January 2009}}

The flight returned to Detroit, but when the crew set the flaps to 35 degrees for landing, the aircraft stabilized in a 1,900 ft/min descent that was far too fast for landing. By applying power to the 1 and 3 engines, McCormick was able to level off the nose and reduce the descent to 700 ft/min. The aircraft touched down at 7:44 pm 1,900 ft down Runway 03R, immediately veering to the right and eventually leaving the runway surface. The first officer, Peter Whitney, applied full reverse thrust to the left engine and idled the right, straightening the aircraft's path, and eventually starting to bring the aircraft back to the runway. The aircraft stopped 8,800 ft from the runway threshold, with the nose and left gear on the runway and the right on the grass beside it.{{Citation needed|date=January 2010}} It happened that while training to convert his expertise to flying the DC-10, McCormick had practiced, in a simulator, controlling the plane with the throttles in this fashion, in the worst-case scenario of a hydraulic failure.<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> A similar technique was used in 1989 following a complete loss of hydraulic pressure on another DC-10, [[United Airlines Flight 232]].{{Citation needed|date=January 2010}}

==Investigation==
The problem that caused the accident was immediately obvious, as the cargo door was missing and had caused damage to the left horizontal stabilizer as it flew off. Investigators immediately studied the maintenance history and found that on 3 March 1972 the handlers reported that the door had not latched electrically and had to be closed manually. On 30 May McDonnell Douglas issued Service Bulletin 52-27, DC-10 SC 612, which called for the upgrading of the electrical wiring that drove the latches because "Three operators have reported failure of the electrical latch actuators to latch/unlatch the cargo doors. Latch actuator failure is attributed to an excessive voltage drop reducing the output torque to the actuator. This condition may prevent electrical latching/unlatching of the hooks."<ref name="NTSB"/> The modification was not compulsory, however, and had not been carried out on N103AA.{{Citation needed|date=January 2010}}

Investigators interviewed the ground crew at Detroit and learned that the cargo loader operating the rear door found it difficult to close. He stated that he closed the door electrically, and waited for the sound of the actuator motors to stop. When they did, he attempted to operate the locking handle, but found it very difficult to close. Adding force with his knee he was able to get the latch to lock, but noticed that the vent plug (see below) was not entirely closed. He brought this to the attention of a mechanic, who cleared the flight. The flight engineer reported that the "door ajar" warning light on his panel was not lit at any time during the taxi out or flight.<ref name="NTSB"/>

Examination of the aircraft and the cargo door, which was recovered largely intact, demonstrated that the latches had not rotated to their locked position. In their locked position, pressure on the door presses the latches further shut, and no force is transmitted into the actuator system that closes and opens them. With the latches only partially closed, forces on the door were transmitted back into the actuator, eventually overwhelming it at about 6,600 lbf. The rapid depressurization when the door broke off caused the floor above it to fail, which pulled the rudder cable to its extension limit and severed several other operating cables.{{Citation needed|date=January 2010}}

==Cause==
{{Unreferenced section|date=January 2010}}
Passenger doors on the DC-10 are of the [[plug door|plug variety]], which prevents the doors from opening while the aircraft is pressurized. The cargo door, however, is not. Due to its large area, the cargo door on the DC-10 could not be swung inside the fuselage without taking up a considerable amount of valuable cargo space. Instead, the door swung outward, allowing cargo to be stored directly behind it. The outward-opening door, in theory, allowed it to be "blown open" by the pressure inside the cargo area.

To prevent this, the DC-10 used a "[[fail safe]]" latching system held in place by "over top dead center latches", five C-shaped latches mounted on a common torque shaft that are rotated over fixed latching pins ("spools") fixed to the aircraft fuselage. Because of their shape, when the latches are in the proper position, pressure on the door does not place torque on the latches that could cause them to open, and actually further seats them on the pins. Normally the latches are opened and closed by a screw jack powered by an electric actuator motor.

Because of the under-designed cabling powering the actuator motor, it was possible for the voltage delivered to the motor to be too small to drive it under high loads. In these cases, the motor would stop turning even if the latches had not rotated over the pins. Since the operators listened for the motors to stop as an indication of their complete rotation, a failure in the drive system during operation would erroneously indicate that the door was properly latched.

To ensure this rotation had completed and the latches were in the proper position, the DC-10 cargo door also included a separate locking mechanism. The locks consisting of small pins that were slid horizontally through holes on the back of the latches, between the latch and the frame of the aircraft. When the pins were in place they mechanically prevented movement back into the open position, so even the actuator motor could no longer open them. If the latches were not in their correct positions, the pins could not enter the holes, and the operating handle on the outside of the door would remain open and visually indicate that there was a problem. Additionally, the handle moved a metal plug into a vent cut in the outer door panel; if the vent was not plugged the door would not retain pressure, eliminating any force on the door. Lastly, there was an indicator light in the cockpit that would remain on if the door was not correctly latched.

In theory, the motor failure on Flight 96 could not present a problem because the locking lever would not be able to close. However, during the investigation a McDonnell Douglas test rig demonstrated that the entire locking pin operating system was too weak, allowing the handle to be forced closed even with the pins out of the locking holes. This occurred on Flight 96, when the handler forced the handle closed with his knee. In spite of the vent not closing completely, neither the handler nor the engineer considered this to be serious. Although the vent door remained partially open, it closed enough to cause it to "blow shut", and thereby allow pressurization of the cargo hold. Although the handle did not seat the pins entirely, the small amount of motion it managed to cause was enough to press on the warning indicator switch, turning the warning light off. It was only the combination of all of these failures that allowed the accident to happen. Yet all of these indicators had a single common point of failure, the mechanical weakness of the locking system that allowed the handle to be moved.

The cabin floor failure was also a matter of poor design. All of the other portions of the cargo holds had holes cut into the cabin floor above the cargo areas. In the case of a pressure loss on either side of the floor, the air would flow through the vents and equalize the pressure, thereby eliminating any force on the floor. Only the rearmost portion of the cabin lacked these holes, and it was that portion that failed. However, because the control cables ran through the floor for the entire length of the aircraft, a failure at any point on the floor would cut controls to the tail section.

==Aftermath==
The NTSB suggested several changes to the system to ensure that the Windsor accident would not recur. These included changes to the locking mechanism to ensure it could not be forced closed, as well as venting cut into the rear cabin floor.{{Citation needed|date=January 2010}}

In response, the [[FAA]], in charge of actually implementing these recommendations, agreed with McDonnell Douglas that the additional venting would be difficult to install. Instead, they proceeded with the modification of the locking system, and additionally added a small clear window set into the bottom of the cargo door that allowed operators to directly inspect whether or not the latches were in place. Combined with the upgrades to the wiring that had already been on the books, this should prevent a repeat of the accident.{{Citation needed|date=January 2010}}

Shortly after the event, [[Dan Applegate]], Director of Product Engineering at [[Convair]], wrote a memo to [[Convair]] management pointing out several problems with the door design. McDonnell Douglas had subcontracted design and construction of the DC-10 fuselage to Convair, and Applegate had overseen its development in ways that he felt were reducing the safety of the system. In particular, he noted that the actuator system had been switched from a hydraulic system to an electrical one, which he felt was less safe. He also noted that the floor would be prone to failure if the door was lost, and this would likely sever the control cables, leading to a loss of the aircraft. Finally, he pointed out that this precise failure had already occurred in ground testing in 1970, and he concluded that such an accident was almost certain to occur again in the future.<ref name = Fielder>John Fielder, Douglas Birsch, [http://books.google.com/books?id=gBHGmwmMj30C&pg=PA4&lpg=PA4&dq=%22Applegate+memorandum%22&source=web&ots=v1rP3bvPYn&sig=V9duWkuQlS7_6CV40EDsLn6t0_E&hl=en&sa=X&oi=book_result&resnum=2&ct=result "The DC-10 Case"], SUNY Press, 1992, ISBN 0791410870</ref>

In spite of these recommendations, two years later [[Turkish Airlines Flight 981]] suffered an almost identical failure, but lost all control of the tail surfaces. The plane crashed outside [[Paris]], killing all 346 passengers and crew onboard. Investigators discovered that the upgrades had never been carried out on this airframe, although the construction logs claimed it had. One modification had been carried out, the installation of the inspection window, along with a placard beside the door controls printed in English and Turkish that informed the operators how to inspect the latches. The operator in Paris was Algerian and could not read either language, and had been instructed that as long as the locking handle closed the door was safe. He also noted that he did not have to force the handle, and investigators concluded that it had already been bent on a prior flight.{{Citation needed|date=January 2010}}

In the aftermath of that accident, the Applegate memorandum was discovered and introduced into evidence during the massive civil lawsuit that followed. Many commentators subsequently blamed the aircraft manufacturer, [[McDonnell Douglas]], and other aviation authorities, for failing to learn lessons from the Flight 96 accident. Although there had been some redesign of the DC-10 cargo door system, it had only been implemented voluntarily and haphazardly by various airlines.{{Citation needed|date=January 2010}} If the warning signs of Flight 96 had been heeded, the Turkish Airlines disaster would have been avoided.<ref name="Air Disaster">[[Macarthur Job]] (1994). ''Air Disaster Volume 1'': pp.136-144</ref><ref name = Fielder/>

A complete redesign of the entire door system followed, and no DC-10 or [[MD-11]] ever suffered a similar accident again.{{Citation needed|date=January 2010}}

N103AA's airframe was broken up at [[Phoenix Goodyear Airport]] in 2002, after being assigned to the [[FedEx]] [[McDonnell Douglas DC-10|MD-10]] program.{{Citation needed|date=May 2008}}

==See also==
* [[Flying an airplane without control surfaces]]
* [[List of notable accidents and incidents on commercial aircraft]]
* [[Uncontrolled decompression#Notable decompression accidents and incidents|List of notable decompression accidents and incidents]]
* [[Loss of control]]
* [[Turkish Airlines Flight 981]]
* [[United Airlines Flight 811]]

==References==
{{Reflist}}

==External links==
*[http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf NTSB Report]



{{Aviation accidents and incidents in 1972}}
{{Mayday NavBox}}

[[Category:Airliner accidents and incidents caused by design or manufacturing errors]]
[[Category:In-flight airliner structural failures]]
[[Category:Accidents and incidents involving the McDonnell Douglas DC-10]]
[[Category:History of Buffalo, New York]]
[[Category:1972 in the United States]]
[[Category:Aviation accidents and incidents in Canada]]
[[Category:American Airlines flights|96]]
[[Category:Aviation accidents and incidents in 1972]]

[[es:Vuelo 96 de American Airlines]]
[[fr:Vol 96 American Airlines]]
[[hu:Az American Airlines 96-os járatának balesete]]
[[nl:American Airlines-vlucht 96]]
[[ja:アメリカン航空96便貨物ドア破損事故]]
[[zh:美國航空96號班機事故]]

American-Airlines-Flug 96

2010-05-04T01:19:49Z

EditorASC: /*Accident details*/Changed section title: see Aviation accidents and incidents

{{Infobox Airliner accident
|Name = American Airlines Flight 96
|Crash image = Aaflight96dc10.png|360px
|Image caption = Artist's depiction of American Airlines Flight 96 losing its aft bulk cargo door
|Date = 12 June 1972|
|Type = Design flaw, Cargo door failure, control failure
|occurrence_type= Accident
|Site = [[Windsor, Ontario]]
|Origin = [[Los Angeles International Airport]]
|Destination = [[LaGuardia Airport]]
|Stopover = [[Detroit Metropolitan Wayne County Airport]]
|Last stopover = [[Buffalo Niagara International Airport]]
|Fatalities = 0
|Injuries = Several minor injuries
|Aircraft Type = [[McDonnell Douglas DC-10|McDonnell Douglas DC-10-10]]
|Operator = [[American Airlines]]
|tail_number = [http://aviation-safety.net/database/record.php?id=19720612-0 N103AA]
|Passengers = 56
|Crew = 11
|Survivors = 67 (All)
}}
'''American Airlines Flight 96''' was a regular [[McDonnell Douglas]] [[DC-10-10]] flight operated by [[American Airlines]]. The flight suffered a cargo door failure on 12 June 1972 while flying over [[Windsor, Ontario]]; it is thus sometimes referred to as the "Windsor incident."<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> The rapid [[Uncontrolled decompression|decompression]] in the cargo hold caused a partial collapse of the passenger compartment floor, which in turn ruptured hydraulic lines, pulled the rudder control cable to its maximum right position, and severed controls to engine number two (the tail engine) leading to serious problems operating the aircraft.<ref name="NTSB">{{cite web
| title = Aircraft Accident Report: American Airlines, Inc. McDonnell Douglas DC-10-10, N103AA. Near Windsor, Ontario, Canada. 12 June 1972.
| publisher = [[National Transportation Safety Board]]
| date = 1973-02-28
| url = http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf
| format = PDF
| accessdate = 2009-03-22 }}
</ref> In spite of [[loss of control|losing almost all control]], the pilots were able to make a safe landing at [[Detroit Metropolitan Wayne County Airport]] with no major injuries.

The cause was later traced to the door latching system, which had failed to close completely. A separate locking system was supposed to ensure this could not happen, but proved to be underdesigned. McDonnell Douglas instituted a number of minor changes to the system to avoid a repeat, but two years later [[Turkish Airlines Flight 981]]'s rear cargo door failed for exactly the same reason, causing the aircraft to lose all control and crash outside [[Paris]] with a loss of 346 passengers and crew, the deadliest air disaster to that point.

==Accident details==
Flight 96 was a regularly scheduled flight from Los Angeles to [[LaGuardia Airport]] with stops in [[Detroit Metropolitan Wayne County Airport]] and [[Buffalo Niagara International Airport]]. On 12 June it was being flown by DC-10-10 N103AA. It left Los Angeles 46 minutes after its scheduled 1:30 pm departure due to passenger loading and traffic, arriving in Detroit at 6:36 pm. At Detroit the majority of the passengers disembarked, and the plane took on new passengers and cargo. Leaving Detroit the aircraft had 56 passengers and 11 crew. The flight departed at 7:20 pm, climbing to 6,000 for a hold before capturing V-554 (a [[victor airway]]), then climb to flight level 210 (21,000 ft).{{Citation needed|date=January 2010}}

At 7:25 pm while climbing through 11,750 ft, the crew heard a distinct "thud" and dirt in the cockpit flew up into their faces. Captain Bryce McCormick reported that he momentarily believed they had suffered a mid-air collision and the cockpit windows had been smashed. At the same time, the rudder pedals moved to their full-left position and the engine controls moved to idle. McCormick immediately took manual control of the aircraft, and attempted to re-apply power, finding that engines 1 and 3 would respond normally, but engine 2, in the tail, would not allow its controls to be moved. McCormick was able to level off and stabilize the speed at 250 knots, although at this speed control was very sluggish. They declared an emergency and requested routing back to Detroit.{{Citation needed|date=January 2010}}

In the cabin, the flight attendants saw a "fog" form within the cabin and immediately recognized it as a depressurization. Two crew were in the rear lounge area, and the floor under their feet partially collapsed into the cargo hold, giving them both minor injuries. In spite of this, the cabin crew immediately attempted to ensure the oxygen masks had deployed properly, but having occurred below the 14,000 ft limit, the masks had not deployed. One of the attendants obtained a walk-around oxygen bottle and called the cockpit on the intercom to inform them that the damage was in the rear of the aircraft. On instructions from the cabin, the attendants instructed the passengers on emergency landing procedures. A number of passengers later reported that the aircraft safety cards proved useful in locating the nearest exit.{{Citation needed|date=January 2009}}

The flight returned to Detroit, but when the crew set the flaps to 35 degrees for landing, the aircraft stabilized in a 1,900 ft/min descent that was far too fast for landing. By applying power to the 1 and 3 engines, McCormick was able to level off the nose and reduce the descent to 700 ft/min. The aircraft touched down at 7:44 pm 1,900 ft down Runway 03R, immediately veering to the right and eventually leaving the runway surface. The first officer, Peter Whitney, applied full reverse thrust to the left engine and idled the right, straightening the aircraft's path, and eventually starting to bring the aircraft back to the runway. The aircraft stopped 8,800 ft from the runway threshold, with the nose and left gear on the runway and the right on the grass beside it.{{Citation needed|date=January 2010}} It happened that while training to convert his expertise to flying the DC-10, McCormick had practiced, in a simulator, controlling the plane with the throttles in this fashion, in the worst-case scenario of a hydraulic failure.<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> A similar technique was used in 1989 following a complete loss of hydraulic pressure on another DC-10, [[United Airlines Flight 232]].{{Citation needed|date=January 2010}}

==Investigation==
The problem that caused the accident was immediately obvious, as the cargo door was missing and had caused damage to the left horizontal stabilizer as it flew off. Investigators immediately studied the maintenance history and found that on 3 March 1972 the handlers reported that the door had not latched electrically and had to be closed manually. On 30 May McDonnell Douglas issued Service Bulletin 52-27, DC-10 SC 612, which called for the upgrading of the electrical wiring that drove the latches because "Three operators have reported failure of the electrical latch actuators to latch/unlatch the cargo doors. Latch actuator failure is attributed to an excessive voltage drop reducing the output torque to the actuator. This condition may prevent electrical latching/unlatching of the hooks."<ref name="NTSB"/> The modification was not compulsory, however, and had not been carried out on N103AA.{{Citation needed|date=January 2010}}

Investigators interviewed the ground crew at Detroit and learned that the cargo loader operating the rear door found it difficult to close. He stated that he closed the door electrically, and waited for the sound of the actuator motors to stop. When they did, he attempted to operate the locking handle, but found it very difficult to close. Adding force with his knee he was able to get the latch to lock, but noticed that the vent plug (see below) was not entirely closed. He brought this to the attention of a mechanic, who cleared the flight. The flight engineer reported that the "door ajar" warning light on his panel was not lit at any time during the taxi out or flight.<ref name="NTSB"/>

Examination of the aircraft and the cargo door, which was recovered largely intact, demonstrated that the latches had not rotated to their locked position. In their locked position, pressure on the door presses the latches further shut, and no force is transmitted into the actuator system that closes and opens them. With the latches only partially closed, forces on the door were transmitted back into the actuator, eventually overwhelming it at about 6,600 lbf. The rapid depressurization when the door broke off caused the floor above it to fail, which pulled the rudder cable to its extension limit and severed several other operating cables.{{Citation needed|date=January 2010}}

==Cause==
{{Unreferenced section|date=January 2010}}
Passenger doors on the DC-10 are of the [[plug door|plug variety]], which prevents the doors from opening while the aircraft is pressurized. The cargo door, however, is not. Due to its large area, the cargo door on the DC-10 could not be swung inside the fuselage without taking up a considerable amount of valuable cargo space. Instead, the door swung outward, allowing cargo to be stored directly behind it. The outward-opening door, in theory, allowed it to be "blown open" by the pressure inside the cargo area.

To prevent this, the DC-10 used a "[[fail safe]]" latching system held in place by "over top dead center latches", five C-shaped latches mounted on a common torque shaft that are rotated over fixed latching pins ("spools") fixed to the aircraft fuselage. Because of their shape, when the latches are in the proper position, pressure on the door does not place torque on the latches that could cause them to open, and actually further seats them on the pins. Normally the latches are opened and closed by a screw jack powered by an electric actuator motor.

Because of the under-designed cabling powering the actuator motor, it was possible for the voltage delivered to the motor to be too small to drive it under high loads. In these cases, the motor would stop turning even if the latches had not rotated over the pins. Since the operators listened for the motors to stop as an indication of their complete rotation, a failure in the drive system during operation would erroneously indicate that the door was properly latched.

To ensure this rotation had completed and the latches were in the proper position, the DC-10 cargo door also included a separate locking mechanism. The locks consisting of small pins that were slid horizontally through holes on the back of the latches, between the latch and the frame of the aircraft. When the pins were in place they mechanically prevented movement back into the open position, so even the actuator motor could no longer open them. If the latches were not in their correct positions, the pins could not enter the holes, and the operating handle on the outside of the door would remain open and visually indicate that there was a problem. Additionally, the handle moved a metal plug into a vent cut in the outer door panel; if the vent was not plugged the door would not retain pressure, eliminating any force on the door. Lastly, there was an indicator light in the cockpit that would remain on if the door was not correctly latched.

In theory, the motor failure on Flight 96 could not present a problem because the locking lever would not be able to close. However, during the investigation a McDonnell Douglas test rig demonstrated that the entire locking pin operating system was too weak, allowing the handle to be forced closed even with the pins out of the locking holes. This occurred on Flight 96, when the handler forced the handle closed with his knee. In spite of the vent not closing completely, neither the handler nor the engineer considered this to be serious. Although the vent door remained partially open, it closed enough to cause it to "blow shut", and thereby allow pressurization of the cargo hold. Although the handle did not seat the pins entirely, the small amount of motion it managed to cause was enough to press on the warning indicator switch, turning the warning light off. It was only the combination of all of these failures that allowed the accident to happen. Yet all of these indicators had a single common point of failure, the mechanical weakness of the locking system that allowed the handle to be moved.

The cabin floor failure was also a matter of poor design. All of the other portions of the cargo holds had holes cut into the cabin floor above the cargo areas. In the case of a pressure loss on either side of the floor, the air would flow through the vents and equalize the pressure, thereby eliminating any force on the floor. Only the rearmost portion of the cabin lacked these holes, and it was that portion that failed. However, because the control cables ran through the floor for the entire length of the aircraft, a failure at any point on the floor would cut controls to the tail section.

==Aftermath==
The NTSB suggested several changes to the system to ensure that the Windsor accident would not recur. These included changes to the locking mechanism to ensure it could not be forced closed, as well as venting cut into the rear cabin floor.{{Citation needed|date=January 2010}}

In response, the [[FAA]], in charge of actually implementing these recommendations, agreed with McDonnell Douglas that the additional venting would be difficult to install. Instead, they proceeded with the modification of the locking system, and additionally added a small clear window set into the bottom of the cargo door that allowed operators to directly inspect whether or not the latches were in place. Combined with the upgrades to the wiring that had already been on the books, this should prevent a repeat of the accident.{{Citation needed|date=January 2010}}

Shortly after the event, [[Dan Applegate]], Director of Product Engineering at [[Convair]], wrote a memo to [[Convair]] management pointing out several problems with the door design. McDonnell Douglas had subcontracted design and construction of the DC-10 fuselage to Convair, and Applegate had overseen its development in ways that he felt were reducing the safety of the system. In particular, he noted that the actuator system had been switched from a hydraulic system to an electrical one, which he felt was less safe. He also noted that the floor would be prone to failure if the door was lost, and this would likely sever the control cables, leading to a loss of the aircraft. Finally, he pointed out that this precise failure had already occurred in ground testing in 1970, and he concluded that such an accident was almost certain to occur again in the future.<ref name = Fielder>John Fielder, Douglas Birsch, [http://books.google.com/books?id=gBHGmwmMj30C&pg=PA4&lpg=PA4&dq=%22Applegate+memorandum%22&source=web&ots=v1rP3bvPYn&sig=V9duWkuQlS7_6CV40EDsLn6t0_E&hl=en&sa=X&oi=book_result&resnum=2&ct=result "The DC-10 Case"], SUNY Press, 1992, ISBN 0791410870</ref>

In spite of these recommendations, two years later [[Turkish Airlines Flight 981]] suffered an almost identical failure, but lost all control of the tail surfaces. The plane crashed outside [[Paris]], killing all 346 passengers and crew onboard. Investigators discovered that the upgrades had never been carried out on this airframe, although the construction logs claimed it had. One modification had been carried out, the installation of the inspection window, along with a placard beside the door controls printed in English and Turkish that informed the operators how to inspect the latches. The operator in Paris was Algerian and could not read either language, and had been instructed that as long as the locking handle closed the door was safe. He also noted that he did not have to force the handle, and investigators concluded that it had already been bent on a prior flight.{{Citation needed|date=January 2010}}

In the aftermath of that accident, the Applegate memorandum was discovered and introduced into evidence during the massive civil lawsuit that followed. Many commentators subsequently blamed the aircraft manufacturer, [[McDonnell Douglas]], and other aviation authorities, for failing to learn lessons from the Flight 96 accident. Although there had been some redesign of the DC-10 cargo door system, it had only been implemented voluntarily and haphazardly by various airlines.{{Citation needed|date=January 2010}} If the warning signs of Flight 96 had been heeded, the Turkish Airlines disaster would have been avoided.<ref name="Air Disaster">[[Macarthur Job]] (1994). ''Air Disaster Volume 1'': pp.136-144</ref><ref name = Fielder/>

A complete redesign of the entire door system followed, and no DC-10 or [[MD-11]] ever suffered a similar accident again.{{Citation needed|date=January 2010}}

N103AA's airframe was broken up at [[Phoenix Goodyear Airport]] in 2002, after being assigned to the [[FedEx]] [[McDonnell Douglas DC-10|MD-10]] program.{{Citation needed|date=May 2008}}

==See also==
* [[Flying an airplane without control surfaces]]
* [[List of notable accidents and incidents on commercial aircraft]]
* [[Uncontrolled decompression#Notable decompression accidents and incidents|List of notable decompression accidents and incidents]]
* [[Loss of control]]
* [[Turkish Airlines Flight 981]]
* [[United Airlines Flight 811]]

==References==
{{Reflist}}

==External links==
*[http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf NTSB Report]



{{Aviation accidents and incidents in 1972}}
{{Mayday NavBox}}

[[Category:Airliner accidents and incidents caused by design or manufacturing errors]]
[[Category:In-flight airliner structural failures]]
[[Category:Accidents and incidents involving the McDonnell Douglas DC-10]]
[[Category:History of Buffalo, New York]]
[[Category:1972 in the United States]]
[[Category:Aviation accidents and incidents in Canada]]
[[Category:American Airlines flights|96]]
[[Category:Aviation accidents and incidents in 1972]]

[[es:Vuelo 96 de American Airlines]]
[[fr:Vol 96 American Airlines]]
[[hu:Az American Airlines 96-os járatának balesete]]
[[nl:American Airlines-vlucht 96]]
[[ja:アメリカン航空96便貨物ドア破損事故]]
[[zh:美國航空96號班機事故]]

American-Airlines-Flug 96

2010-05-04T01:16:43Z

EditorASC: Undid revision 359967348 by EditorASC (talk)

{{Infobox Airliner accident
|Name = American Airlines Flight 96
|Crash image = Aaflight96dc10.png|360px
|Image caption = Artist's depiction of American Airlines Flight 96 losing its aft bulk cargo door
|Date = 12 June 1972|
|Type = Design flaw, Cargo door failure, control failure
|occurrence_type= Accident
|Site = [[Windsor, Ontario]]
|Origin = [[Los Angeles International Airport]]
|Destination = [[LaGuardia Airport]]
|Stopover = [[Detroit Metropolitan Wayne County Airport]]
|Last stopover = [[Buffalo Niagara International Airport]]
|Fatalities = 0
|Injuries = Several minor injuries
|Aircraft Type = [[McDonnell Douglas DC-10|McDonnell Douglas DC-10-10]]
|Operator = [[American Airlines]]
|tail_number = [http://aviation-safety.net/database/record.php?id=19720612-0 N103AA]
|Passengers = 56
|Crew = 11
|Survivors = 67 (All)
}}
'''American Airlines Flight 96''' was a regular [[McDonnell Douglas]] [[DC-10-10]] flight operated by [[American Airlines]]. The flight suffered a cargo door failure on 12 June 1972 while flying over [[Windsor, Ontario]]; it is thus sometimes referred to as the "Windsor incident."<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> The rapid [[Uncontrolled decompression|decompression]] in the cargo hold caused a partial collapse of the passenger compartment floor, which in turn ruptured hydraulic lines, pulled the rudder control cable to its maximum right position, and severed controls to engine number two (the tail engine) leading to serious problems operating the aircraft.<ref name="NTSB">{{cite web
| title = Aircraft Accident Report: American Airlines, Inc. McDonnell Douglas DC-10-10, N103AA. Near Windsor, Ontario, Canada. 12 June 1972.
| publisher = [[National Transportation Safety Board]]
| date = 1973-02-28
| url = http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf
| format = PDF
| accessdate = 2009-03-22 }}
</ref> In spite of [[loss of control|losing almost all control]], the pilots were able to make a safe landing at [[Detroit Metropolitan Wayne County Airport]] with no major injuries.

The cause was later traced to the door latching system, which had failed to close completely. A separate locking system was supposed to ensure this could not happen, but proved to be underdesigned. McDonnell Douglas instituted a number of minor changes to the system to avoid a repeat, but two years later [[Turkish Airlines Flight 981]]'s rear cargo door failed for exactly the same reason, causing the aircraft to lose all control and crash outside [[Paris]] with a loss of 346 passengers and crew, the deadliest air disaster to that point.

==Incident==
Flight 96 was a regularly scheduled flight from Los Angeles to [[LaGuardia Airport]] with stops in [[Detroit Metropolitan Wayne County Airport]] and [[Buffalo Niagara International Airport]]. On 12 June it was being flown by DC-10-10 N103AA. It left Los Angeles 46 minutes after its scheduled 1:30 pm departure due to passenger loading and traffic, arriving in Detroit at 6:36 pm. At Detroit the majority of the passengers disembarked, and the plane took on new passengers and cargo. Leaving Detroit the aircraft had 56 passengers and 11 crew. The flight departed at 7:20 pm, climbing to 6,000 for a hold before capturing V-554 (a [[victor airway]]), then climb to flight level 210 (21,000 ft).{{Citation needed|date=January 2010}}

At 7:25 pm while climbing through 11,750 ft, the crew heard a distinct "thud" and dirt in the cockpit flew up into their faces. Captain Bryce McCormick reported that he momentarily believed they had suffered a mid-air collision and the cockpit windows had been smashed. At the same time, the rudder pedals moved to their full-left position and the engine controls moved to idle. McCormick immediately took manual control of the aircraft, and attempted to re-apply power, finding that engines 1 and 3 would respond normally, but engine 2, in the tail, would not allow its controls to be moved. McCormick was able to level off and stabilize the speed at 250 knots, although at this speed control was very sluggish. They declared an emergency and requested routing back to Detroit.{{Citation needed|date=January 2010}}

In the cabin, the flight attendants saw a "fog" form within the cabin and immediately recognized it as a depressurization. Two crew were in the rear lounge area, and the floor under their feet partially collapsed into the cargo hold, giving them both minor injuries. In spite of this, the cabin crew immediately attempted to ensure the oxygen masks had deployed properly, but having occurred below the 14,000 ft limit, the masks had not deployed. One of the attendants obtained a walk-around oxygen bottle and called the cockpit on the intercom to inform them that the damage was in the rear of the aircraft. On instructions from the cabin, the attendants instructed the passengers on emergency landing procedures. A number of passengers later reported that the aircraft safety cards proved useful in locating the nearest exit.{{Citation needed|date=January 2009}}

The flight returned to Detroit, but when the crew set the flaps to 35 degrees for landing, the aircraft stabilized in a 1,900 ft/min descent that was far too fast for landing. By applying power to the 1 and 3 engines, McCormick was able to level off the nose and reduce the descent to 700 ft/min. The aircraft touched down at 7:44 pm 1,900 ft down Runway 03R, immediately veering to the right and eventually leaving the runway surface. The first officer, Peter Whitney, applied full reverse thrust to the left engine and idled the right, straightening the aircraft's path, and eventually starting to bring the aircraft back to the runway. The aircraft stopped 8,800 ft from the runway threshold, with the nose and left gear on the runway and the right on the grass beside it.{{Citation needed|date=January 2010}} It happened that while training to convert his expertise to flying the DC-10, McCormick had practiced, in a simulator, controlling the plane with the throttles in this fashion, in the worst-case scenario of a hydraulic failure.<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> A similar technique was used in 1989 following a complete loss of hydraulic pressure on another DC-10, [[United Airlines Flight 232]].{{Citation needed|date=January 2010}}

==Investigation==
The problem that caused the accident was immediately obvious, as the cargo door was missing and had caused damage to the left horizontal stabilizer as it flew off. Investigators immediately studied the maintenance history and found that on 3 March 1972 the handlers reported that the door had not latched electrically and had to be closed manually. On 30 May McDonnell Douglas issued Service Bulletin 52-27, DC-10 SC 612, which called for the upgrading of the electrical wiring that drove the latches because "Three operators have reported failure of the electrical latch actuators to latch/unlatch the cargo doors. Latch actuator failure is attributed to an excessive voltage drop reducing the output torque to the actuator. This condition may prevent electrical latching/unlatching of the hooks."<ref name="NTSB"/> The modification was not compulsory, however, and had not been carried out on N103AA.{{Citation needed|date=January 2010}}

Investigators interviewed the ground crew at Detroit and learned that the cargo loader operating the rear door found it difficult to close. He stated that he closed the door electrically, and waited for the sound of the actuator motors to stop. When they did, he attempted to operate the locking handle, but found it very difficult to close. Adding force with his knee he was able to get the latch to lock, but noticed that the vent plug (see below) was not entirely closed. He brought this to the attention of a mechanic, who cleared the flight. The flight engineer reported that the "door ajar" warning light on his panel was not lit at any time during the taxi out or flight.<ref name="NTSB"/>

Examination of the aircraft and the cargo door, which was recovered largely intact, demonstrated that the latches had not rotated to their locked position. In their locked position, pressure on the door presses the latches further shut, and no force is transmitted into the actuator system that closes and opens them. With the latches only partially closed, forces on the door were transmitted back into the actuator, eventually overwhelming it at about 6,600 lbf. The rapid depressurization when the door broke off caused the floor above it to fail, which pulled the rudder cable to its extension limit and severed several other operating cables.{{Citation needed|date=January 2010}}

==Cause==
{{Unreferenced section|date=January 2010}}
Passenger doors on the DC-10 are of the [[plug door|plug variety]], which prevents the doors from opening while the aircraft is pressurized. The cargo door, however, is not. Due to its large area, the cargo door on the DC-10 could not be swung inside the fuselage without taking up a considerable amount of valuable cargo space. Instead, the door swung outward, allowing cargo to be stored directly behind it. The outward-opening door, in theory, allowed it to be "blown open" by the pressure inside the cargo area.

To prevent this, the DC-10 used a "[[fail safe]]" latching system held in place by "over top dead center latches", five C-shaped latches mounted on a common torque shaft that are rotated over fixed latching pins ("spools") fixed to the aircraft fuselage. Because of their shape, when the latches are in the proper position, pressure on the door does not place torque on the latches that could cause them to open, and actually further seats them on the pins. Normally the latches are opened and closed by a screw jack powered by an electric actuator motor.

Because of the under-designed cabling powering the actuator motor, it was possible for the voltage delivered to the motor to be too small to drive it under high loads. In these cases, the motor would stop turning even if the latches had not rotated over the pins. Since the operators listened for the motors to stop as an indication of their complete rotation, a failure in the drive system during operation would erroneously indicate that the door was properly latched.

To ensure this rotation had completed and the latches were in the proper position, the DC-10 cargo door also included a separate locking mechanism. The locks consisting of small pins that were slid horizontally through holes on the back of the latches, between the latch and the frame of the aircraft. When the pins were in place they mechanically prevented movement back into the open position, so even the actuator motor could no longer open them. If the latches were not in their correct positions, the pins could not enter the holes, and the operating handle on the outside of the door would remain open and visually indicate that there was a problem. Additionally, the handle moved a metal plug into a vent cut in the outer door panel; if the vent was not plugged the door would not retain pressure, eliminating any force on the door. Lastly, there was an indicator light in the cockpit that would remain on if the door was not correctly latched.

In theory, the motor failure on Flight 96 could not present a problem because the locking lever would not be able to close. However, during the investigation a McDonnell Douglas test rig demonstrated that the entire locking pin operating system was too weak, allowing the handle to be forced closed even with the pins out of the locking holes. This occurred on Flight 96, when the handler forced the handle closed with his knee. In spite of the vent not closing completely, neither the handler nor the engineer considered this to be serious. Although the vent door remained partially open, it closed enough to cause it to "blow shut", and thereby allow pressurization of the cargo hold. Although the handle did not seat the pins entirely, the small amount of motion it managed to cause was enough to press on the warning indicator switch, turning the warning light off. It was only the combination of all of these failures that allowed the accident to happen. Yet all of these indicators had a single common point of failure, the mechanical weakness of the locking system that allowed the handle to be moved.

The cabin floor failure was also a matter of poor design. All of the other portions of the cargo holds had holes cut into the cabin floor above the cargo areas. In the case of a pressure loss on either side of the floor, the air would flow through the vents and equalize the pressure, thereby eliminating any force on the floor. Only the rearmost portion of the cabin lacked these holes, and it was that portion that failed. However, because the control cables ran through the floor for the entire length of the aircraft, a failure at any point on the floor would cut controls to the tail section.

==Aftermath==
The NTSB suggested several changes to the system to ensure that the Windsor accident would not recur. These included changes to the locking mechanism to ensure it could not be forced closed, as well as venting cut into the rear cabin floor.{{Citation needed|date=January 2010}}

In response, the [[FAA]], in charge of actually implementing these recommendations, agreed with McDonnell Douglas that the additional venting would be difficult to install. Instead, they proceeded with the modification of the locking system, and additionally added a small clear window set into the bottom of the cargo door that allowed operators to directly inspect whether or not the latches were in place. Combined with the upgrades to the wiring that had already been on the books, this should prevent a repeat of the accident.{{Citation needed|date=January 2010}}

Shortly after the event, [[Dan Applegate]], Director of Product Engineering at [[Convair]], wrote a memo to [[Convair]] management pointing out several problems with the door design. McDonnell Douglas had subcontracted design and construction of the DC-10 fuselage to Convair, and Applegate had overseen its development in ways that he felt were reducing the safety of the system. In particular, he noted that the actuator system had been switched from a hydraulic system to an electrical one, which he felt was less safe. He also noted that the floor would be prone to failure if the door was lost, and this would likely sever the control cables, leading to a loss of the aircraft. Finally, he pointed out that this precise failure had already occurred in ground testing in 1970, and he concluded that such an accident was almost certain to occur again in the future.<ref name = Fielder>John Fielder, Douglas Birsch, [http://books.google.com/books?id=gBHGmwmMj30C&pg=PA4&lpg=PA4&dq=%22Applegate+memorandum%22&source=web&ots=v1rP3bvPYn&sig=V9duWkuQlS7_6CV40EDsLn6t0_E&hl=en&sa=X&oi=book_result&resnum=2&ct=result "The DC-10 Case"], SUNY Press, 1992, ISBN 0791410870</ref>

In spite of these recommendations, two years later [[Turkish Airlines Flight 981]] suffered an almost identical failure, but lost all control of the tail surfaces. The plane crashed outside [[Paris]], killing all 346 passengers and crew onboard. Investigators discovered that the upgrades had never been carried out on this airframe, although the construction logs claimed it had. One modification had been carried out, the installation of the inspection window, along with a placard beside the door controls printed in English and Turkish that informed the operators how to inspect the latches. The operator in Paris was Algerian and could not read either language, and had been instructed that as long as the locking handle closed the door was safe. He also noted that he did not have to force the handle, and investigators concluded that it had already been bent on a prior flight.{{Citation needed|date=January 2010}}

In the aftermath of that accident, the Applegate memorandum was discovered and introduced into evidence during the massive civil lawsuit that followed. Many commentators subsequently blamed the aircraft manufacturer, [[McDonnell Douglas]], and other aviation authorities, for failing to learn lessons from the Flight 96 accident. Although there had been some redesign of the DC-10 cargo door system, it had only been implemented voluntarily and haphazardly by various airlines.{{Citation needed|date=January 2010}} If the warning signs of Flight 96 had been heeded, the Turkish Airlines disaster would have been avoided.<ref name="Air Disaster">[[Macarthur Job]] (1994). ''Air Disaster Volume 1'': pp.136-144</ref><ref name = Fielder/>

A complete redesign of the entire door system followed, and no DC-10 or [[MD-11]] ever suffered a similar accident again.{{Citation needed|date=January 2010}}

N103AA's airframe was broken up at [[Phoenix Goodyear Airport]] in 2002, after being assigned to the [[FedEx]] [[McDonnell Douglas DC-10|MD-10]] program.{{Citation needed|date=May 2008}}

==See also==
* [[Flying an airplane without control surfaces]]
* [[List of notable accidents and incidents on commercial aircraft]]
* [[Uncontrolled decompression#Notable decompression accidents and incidents|List of notable decompression accidents and incidents]]
* [[Loss of control]]
* [[Turkish Airlines Flight 981]]
* [[United Airlines Flight 811]]

==References==
{{Reflist}}

==External links==
*[http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf NTSB Report]



{{Aviation accidents and incidents in 1972}}
{{Mayday NavBox}}

[[Category:Airliner accidents and incidents caused by design or manufacturing errors]]
[[Category:In-flight airliner structural failures]]
[[Category:Accidents and incidents involving the McDonnell Douglas DC-10]]
[[Category:History of Buffalo, New York]]
[[Category:1972 in the United States]]
[[Category:Aviation accidents and incidents in Canada]]
[[Category:American Airlines flights|96]]
[[Category:Aviation accidents and incidents in 1972]]

[[es:Vuelo 96 de American Airlines]]
[[fr:Vol 96 American Airlines]]
[[hu:Az American Airlines 96-os járatának balesete]]
[[nl:American Airlines-vlucht 96]]
[[ja:アメリカン航空96便貨物ドア破損事故]]
[[zh:美國航空96號班機事故]]

American-Airlines-Flug 96

2010-05-04T01:12:04Z

EditorASC: /* Accident details */ Changed section title; see http://en.wikipedia.org/wiki/Aviation_incidents_and_accidents

{{Infobox Airliner accident
|Name = American Airlines Flight 96
|Crash image = Aaflight96dc10.png|360px
|Image caption = Artist's depiction of American Airlines Flight 96 losing its aft bulk cargo door
|Date = 12 June 1972|
|Type = Design flaw, Cargo door failure, control failure
|occurrence_type= Accident
|Site = [[Windsor, Ontario]]
|Origin = [[Los Angeles International Airport]]
|Destination = [[LaGuardia Airport]]
|Stopover = [[Detroit Metropolitan Wayne County Airport]]
|Last stopover = [[Buffalo Niagara International Airport]]
|Fatalities = 0
|Injuries = Several minor injuries
|Aircraft Type = [[McDonnell Douglas DC-10|McDonnell Douglas DC-10-10]]
|Operator = [[American Airlines]]
|tail_number = [http://aviation-safety.net/database/record.php?id=19720612-0 N103AA]
|Passengers = 56
|Crew = 11
|Survivors = 67 (All)
}}
'''American Airlines Flight 96''' was a regular [[McDonnell Douglas]] [[DC-10-10]] flight operated by [[American Airlines]]. The flight suffered a cargo door failure on 12 June 1972 while flying over [[Windsor, Ontario]]; it is thus sometimes referred to as the "Windsor incident."<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> The rapid [[Uncontrolled decompression|decompression]] in the cargo hold caused a partial collapse of the passenger compartment floor, which in turn ruptured hydraulic lines, pulled the rudder control cable to its maximum right position, and severed controls to engine number two (the tail engine) leading to serious problems operating the aircraft.<ref name="NTSB">{{cite web
| title = Aircraft Accident Report: American Airlines, Inc. McDonnell Douglas DC-10-10, N103AA. Near Windsor, Ontario, Canada. 12 June 1972.
| publisher = [[National Transportation Safety Board]]
| date = 1973-02-28
| url = http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf
| format = PDF
| accessdate = 2009-03-22 }}
</ref> In spite of [[loss of control|losing almost all control]], the pilots were able to make a safe landing at [[Detroit Metropolitan Wayne County Airport]] with no major injuries.

The cause was later traced to the door latching system, which had failed to close completely. A separate locking system was supposed to ensure this could not happen, but proved to be underdesigned. McDonnell Douglas instituted a number of minor changes to the system to avoid a repeat, but two years later [[Turkish Airlines Flight 981]]'s rear cargo door failed for exactly the same reason, causing the aircraft to lose all control and crash outside [[Paris]] with a loss of 346 passengers and crew, the deadliest air disaster to that point.

==Accident details==
Flight 96 was a regularly scheduled flight from Los Angeles to [[LaGuardia Airport]] with stops in [[Detroit Metropolitan Wayne County Airport]] and [[Buffalo Niagara International Airport]]. On 12 June it was being flown by DC-10-10 N103AA. It left Los Angeles 46 minutes after its scheduled 1:30 pm departure due to passenger loading and traffic, arriving in Detroit at 6:36 pm. At Detroit the majority of the passengers disembarked, and the plane took on new passengers and cargo. Leaving Detroit the aircraft had 56 passengers and 11 crew. The flight departed at 7:20 pm, climbing to 6,000 for a hold before capturing V-554 (a [[victor airway]]), then climb to flight level 210 (21,000 ft).{{Citation needed|date=January 2010}}

At 7:25 pm while climbing through 11,750 ft, the crew heard a distinct "thud" and dirt in the cockpit flew up into their faces. Captain Bryce McCormick reported that he momentarily believed they had suffered a mid-air collision and the cockpit windows had been smashed. At the same time, the rudder pedals moved to their full-left position and the engine controls moved to idle. McCormick immediately took manual control of the aircraft, and attempted to re-apply power, finding that engines 1 and 3 would respond normally, but engine 2, in the tail, would not allow its controls to be moved. McCormick was able to level off and stabilize the speed at 250 knots, although at this speed control was very sluggish. They declared an emergency and requested routing back to Detroit.{{Citation needed|date=January 2010}}

In the cabin, the flight attendants saw a "fog" form within the cabin and immediately recognized it as a depressurization. Two crew were in the rear lounge area, and the floor under their feet partially collapsed into the cargo hold, giving them both minor injuries. In spite of this, the cabin crew immediately attempted to ensure the oxygen masks had deployed properly, but having occurred below the 14,000 ft limit, the masks had not deployed. One of the attendants obtained a walk-around oxygen bottle and called the cockpit on the intercom to inform them that the damage was in the rear of the aircraft. On instructions from the cabin, the attendants instructed the passengers on emergency landing procedures. A number of passengers later reported that the aircraft safety cards proved useful in locating the nearest exit.{{Citation needed|date=January 2009}}

The flight returned to Detroit, but when the crew set the flaps to 35 degrees for landing, the aircraft stabilized in a 1,900 ft/min descent that was far too fast for landing. By applying power to the 1 and 3 engines, McCormick was able to level off the nose and reduce the descent to 700 ft/min. The aircraft touched down at 7:44 pm 1,900 ft down Runway 03R, immediately veering to the right and eventually leaving the runway surface. The first officer, Peter Whitney, applied full reverse thrust to the left engine and idled the right, straightening the aircraft's path, and eventually starting to bring the aircraft back to the runway. The aircraft stopped 8,800 ft from the runway threshold, with the nose and left gear on the runway and the right on the grass beside it.{{Citation needed|date=January 2010}} It happened that while training to convert his expertise to flying the DC-10, McCormick had practiced, in a simulator, controlling the plane with the throttles in this fashion, in the worst-case scenario of a hydraulic failure.<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> A similar technique was used in 1989 following a complete loss of hydraulic pressure on another DC-10, [[United Airlines Flight 232]].{{Citation needed|date=January 2010}}

==Investigation==
The problem that caused the accident was immediately obvious, as the cargo door was missing and had caused damage to the left horizontal stabilizer as it flew off. Investigators immediately studied the maintenance history and found that on 3 March 1972 the handlers reported that the door had not latched electrically and had to be closed manually. On 30 May McDonnell Douglas issued Service Bulletin 52-27, DC-10 SC 612, which called for the upgrading of the electrical wiring that drove the latches because "Three operators have reported failure of the electrical latch actuators to latch/unlatch the cargo doors. Latch actuator failure is attributed to an excessive voltage drop reducing the output torque to the actuator. This condition may prevent electrical latching/unlatching of the hooks."<ref name="NTSB"/> The modification was not compulsory, however, and had not been carried out on N103AA.{{Citation needed|date=January 2010}}

Investigators interviewed the ground crew at Detroit and learned that the cargo loader operating the rear door found it difficult to close. He stated that he closed the door electrically, and waited for the sound of the actuator motors to stop. When they did, he attempted to operate the locking handle, but found it very difficult to close. Adding force with his knee he was able to get the latch to lock, but noticed that the vent plug (see below) was not entirely closed. He brought this to the attention of a mechanic, who cleared the flight. The flight engineer reported that the "door ajar" warning light on his panel was not lit at any time during the taxi out or flight.<ref name="NTSB"/>

Examination of the aircraft and the cargo door, which was recovered largely intact, demonstrated that the latches had not rotated to their locked position. In their locked position, pressure on the door presses the latches further shut, and no force is transmitted into the actuator system that closes and opens them. With the latches only partially closed, forces on the door were transmitted back into the actuator, eventually overwhelming it at about 6,600 lbf. The rapid depressurization when the door broke off caused the floor above it to fail, which pulled the rudder cable to its extension limit and severed several other operating cables.{{Citation needed|date=January 2010}}

==Cause==
{{Unreferenced section|date=January 2010}}
Passenger doors on the DC-10 are of the [[plug door|plug variety]], which prevents the doors from opening while the aircraft is pressurized. The cargo door, however, is not. Due to its large area, the cargo door on the DC-10 could not be swung inside the fuselage without taking up a considerable amount of valuable cargo space. Instead, the door swung outward, allowing cargo to be stored directly behind it. The outward-opening door, in theory, allowed it to be "blown open" by the pressure inside the cargo area.

To prevent this, the DC-10 used a "[[fail safe]]" latching system held in place by "over top dead center latches", five C-shaped latches mounted on a common torque shaft that are rotated over fixed latching pins ("spools") fixed to the aircraft fuselage. Because of their shape, when the latches are in the proper position, pressure on the door does not place torque on the latches that could cause them to open, and actually further seats them on the pins. Normally the latches are opened and closed by a screw jack powered by an electric actuator motor.

Because of the under-designed cabling powering the actuator motor, it was possible for the voltage delivered to the motor to be too small to drive it under high loads. In these cases, the motor would stop turning even if the latches had not rotated over the pins. Since the operators listened for the motors to stop as an indication of their complete rotation, a failure in the drive system during operation would erroneously indicate that the door was properly latched.

To ensure this rotation had completed and the latches were in the proper position, the DC-10 cargo door also included a separate locking mechanism. The locks consisting of small pins that were slid horizontally through holes on the back of the latches, between the latch and the frame of the aircraft. When the pins were in place they mechanically prevented movement back into the open position, so even the actuator motor could no longer open them. If the latches were not in their correct positions, the pins could not enter the holes, and the operating handle on the outside of the door would remain open and visually indicate that there was a problem. Additionally, the handle moved a metal plug into a vent cut in the outer door panel; if the vent was not plugged the door would not retain pressure, eliminating any force on the door. Lastly, there was an indicator light in the cockpit that would remain on if the door was not correctly latched.

In theory, the motor failure on Flight 96 could not present a problem because the locking lever would not be able to close. However, during the investigation a McDonnell Douglas test rig demonstrated that the entire locking pin operating system was too weak, allowing the handle to be forced closed even with the pins out of the locking holes. This occurred on Flight 96, when the handler forced the handle closed with his knee. In spite of the vent not closing completely, neither the handler nor the engineer considered this to be serious. Although the vent door remained partially open, it closed enough to cause it to "blow shut", and thereby allow pressurization of the cargo hold. Although the handle did not seat the pins entirely, the small amount of motion it managed to cause was enough to press on the warning indicator switch, turning the warning light off. It was only the combination of all of these failures that allowed the accident to happen. Yet all of these indicators had a single common point of failure, the mechanical weakness of the locking system that allowed the handle to be moved.

The cabin floor failure was also a matter of poor design. All of the other portions of the cargo holds had holes cut into the cabin floor above the cargo areas. In the case of a pressure loss on either side of the floor, the air would flow through the vents and equalize the pressure, thereby eliminating any force on the floor. Only the rearmost portion of the cabin lacked these holes, and it was that portion that failed. However, because the control cables ran through the floor for the entire length of the aircraft, a failure at any point on the floor would cut controls to the tail section.

==Aftermath==
The NTSB suggested several changes to the system to ensure that the Windsor accident would not recur. These included changes to the locking mechanism to ensure it could not be forced closed, as well as venting cut into the rear cabin floor.{{Citation needed|date=January 2010}}

In response, the [[FAA]], in charge of actually implementing these recommendations, agreed with McDonnell Douglas that the additional venting would be difficult to install. Instead, they proceeded with the modification of the locking system, and additionally added a small clear window set into the bottom of the cargo door that allowed operators to directly inspect whether or not the latches were in place. Combined with the upgrades to the wiring that had already been on the books, this should prevent a repeat of the accident.{{Citation needed|date=January 2010}}

Shortly after the event, [[Dan Applegate]], Director of Product Engineering at [[Convair]], wrote a memo to [[Convair]] management pointing out several problems with the door design. McDonnell Douglas had subcontracted design and construction of the DC-10 fuselage to Convair, and Applegate had overseen its development in ways that he felt were reducing the safety of the system. In particular, he noted that the actuator system had been switched from a hydraulic system to an electrical one, which he felt was less safe. He also noted that the floor would be prone to failure if the door was lost, and this would likely sever the control cables, leading to a loss of the aircraft. Finally, he pointed out that this precise failure had already occurred in ground testing in 1970, and he concluded that such an accident was almost certain to occur again in the future.<ref name = Fielder>John Fielder, Douglas Birsch, [http://books.google.com/books?id=gBHGmwmMj30C&pg=PA4&lpg=PA4&dq=%22Applegate+memorandum%22&source=web&ots=v1rP3bvPYn&sig=V9duWkuQlS7_6CV40EDsLn6t0_E&hl=en&sa=X&oi=book_result&resnum=2&ct=result "The DC-10 Case"], SUNY Press, 1992, ISBN 0791410870</ref>

In spite of these recommendations, two years later [[Turkish Airlines Flight 981]] suffered an almost identical failure, but lost all control of the tail surfaces. The plane crashed outside [[Paris]], killing all 346 passengers and crew onboard. Investigators discovered that the upgrades had never been carried out on this airframe, although the construction logs claimed it had. One modification had been carried out, the installation of the inspection window, along with a placard beside the door controls printed in English and Turkish that informed the operators how to inspect the latches. The operator in Paris was Algerian and could not read either language, and had been instructed that as long as the locking handle closed the door was safe. He also noted that he did not have to force the handle, and investigators concluded that it had already been bent on a prior flight.{{Citation needed|date=January 2010}}

In the aftermath of that accident, the Applegate memorandum was discovered and introduced into evidence during the massive civil lawsuit that followed. Many commentators subsequently blamed the aircraft manufacturer, [[McDonnell Douglas]], and other aviation authorities, for failing to learn lessons from the Flight 96 accident. Although there had been some redesign of the DC-10 cargo door system, it had only been implemented voluntarily and haphazardly by various airlines.{{Citation needed|date=January 2010}} If the warning signs of Flight 96 had been heeded, the Turkish Airlines disaster would have been avoided.<ref name="Air Disaster">[[Macarthur Job]] (1994). ''Air Disaster Volume 1'': pp.136-144</ref><ref name = Fielder/>

A complete redesign of the entire door system followed, and no DC-10 or [[MD-11]] ever suffered a similar accident again.{{Citation needed|date=January 2010}}

N103AA's airframe was broken up at [[Phoenix Goodyear Airport]] in 2002, after being assigned to the [[FedEx]] [[McDonnell Douglas DC-10|MD-10]] program.{{Citation needed|date=May 2008}}

==See also==
* [[Flying an airplane without control surfaces]]
* [[List of notable accidents and incidents on commercial aircraft]]
* [[Uncontrolled decompression#Notable decompression accidents and incidents|List of notable decompression accidents and incidents]]
* [[Loss of control]]
* [[Turkish Airlines Flight 981]]
* [[United Airlines Flight 811]]

==References==
{{Reflist}}

==External links==
*[http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf NTSB Report]



{{Aviation accidents and incidents in 1972}}
{{Mayday NavBox}}

[[Category:Airliner accidents and incidents caused by design or manufacturing errors]]
[[Category:In-flight airliner structural failures]]
[[Category:Accidents and incidents involving the McDonnell Douglas DC-10]]
[[Category:History of Buffalo, New York]]
[[Category:1972 in the United States]]
[[Category:Aviation accidents and incidents in Canada]]
[[Category:American Airlines flights|96]]
[[Category:Aviation accidents and incidents in 1972]]

[[es:Vuelo 96 de American Airlines]]
[[fr:Vol 96 American Airlines]]
[[hu:Az American Airlines 96-os járatának balesete]]
[[nl:American Airlines-vlucht 96]]
[[ja:アメリカン航空96便貨物ドア破損事故]]
[[zh:美國航空96號班機事故]]

American-Airlines-Flug 96

2010-02-26T00:42:04Z

EditorASC: Changed "rear" back to "tail." "Tail engine" is the standard aviation nomenclature, in reference to the number 2 engine, on DC-10 L-1011

{{Infobox Airliner accident
|Name = American Airlines Flight 96
|Crash image = Aaflight96dc10.png|360px
|Image caption = Artist's depiction of American Airlines Flight 96 losing its aft bulk cargo door
|Date = 12 June 1972|
|Type = Design flaw, Cargo door failure, control failure
|occurrence_type= Accident
|Site = [[Windsor, Ontario]]
|Origin = [[Los Angeles International Airport]]
|Destination = [[LaGuardia Airport]]
|Stopover = [[Detroit Metropolitan Wayne County Airport]]
|Last stopover = [[Buffalo Niagara International Airport]]
|Fatalities = 0
|Injuries = Several minor injuries
|Aircraft Type = [[McDonnell Douglas DC-10|McDonnell Douglas DC-10-10]]
|Operator = [[American Airlines]]
|tail_number = [http://aviation-safety.net/database/record.php?id=19720612-0 N103AA]
|Passengers = 56
|Crew = 11
|Survivors = 67 (All)
}}
'''American Airlines Flight 96''' was a regular [[McDonnell Douglas]] [[DC-10-10]] flight operated by [[American Airlines]]. The flight suffered a cargo door failure on 12 June 1972 while flying over [[Windsor, Ontario]]; it is thus sometimes referred to as the "Windsor incident."<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> The rapid [[Uncontrolled decompression|decompression]] in the cargo hold caused a partial collapse of the passenger compartment floor, which in turn ruptured hydraulic lines, pulled the rudder control cable to its maximum right position, and severed controls to engine number two (the tail engine) leading to serious problems operating the aircraft.<ref name="NTSB">{{cite web
| title = Aircraft Accident Report: American Airlines, Inc. McDonnell Douglas DC-10-10, N103AA. Near Windsor, Ontario, Canada. 12 June 1972.
| publisher = [[National Transportation Safety Board]]
| date = 1973-02-28
| url = http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf
| format = PDF
| accessdate = 2009-03-22 }}
</ref> In spite of [[loss of control|losing almost all control]], the pilots were able to make a safe landing at [[Detroit Metropolitan Wayne County Airport]] with no major injuries.

The cause was later traced to the door latching system, which had failed to close completely. A separate locking system was supposed to ensure this could not happen, but proved to be underdesigned. McDonnell Douglas instituted a number of minor changes to the system to avoid a repeat, but two years later [[Turkish Airlines Flight 981]]'s rear cargo door failed for exactly the same reason, causing the aircraft to lose all control and crash outside [[Paris]] with a loss of 346 passengers and crew, the deadliest air disaster to that point.

==Incident==
Flight 96 was a regularly scheduled flight from Los Angeles to [[LaGuardia Airport]] with stops in [[Detroit Metropolitan Wayne County Airport]] and [[Buffalo Niagara International Airport]]. On 12 June it was being flown by DC-10-10 N103AA. It left Los Angeles 46 minutes after its scheduled 1:30 pm departure due to passenger loading and traffic, arriving in Detroit at 6:36 pm. At Detroit the majority of the passengers disembarked, and the plane took on new passengers and cargo. Leaving Detroit the aircraft had 56 passengers and 11 crew. The flight departed at 7:20 pm, climbing to 6,000 for a hold before capturing V-554 (a [[victor airway]]), then climb to flight level 210 (21,000 ft).{{Citation needed|date=January 2010}}

At 7:25 pm while climbing through 11,750 ft, the crew heard a distinct "thud" and dirt in the cockpit flew up into their faces. Captain Bryce McCormick reported that he momentarily believed they had suffered a mid-air collision and the cockpit windows had been smashed. At the same time, the rudder pedals moved to their full-left position and the engine controls moved to idle. McCormick immediately took manual control of the aircraft, and attempted to re-apply power, finding that engines 1 and 3 would respond normally, but engine 2, in the tail, would not allow its controls to be moved. McCormick was able to level off and stabilize the speed at 250 knots, although at this speed control was very sluggish. They declared an emergency and requested routing back to Detroit.{{Citation needed|date=January 2010}}

In the cabin, the flight attendants saw a "fog" form within the cabin and immediately recognized it as a depressurization. Two crew were in the rear lounge area, and the floor under their feet partially collapsed into the cargo hold, giving them both minor injuries. In spite of this, the cabin crew immediately attempted to ensure the oxygen masks had deployed properly, but having occurred below the 14,000 ft limit, the masks had not deployed. One of the attendants obtained a walk-around oxygen bottle and called the cockpit on the intercom to inform them that the damage was in the rear of the aircraft. On instructions from the cabin, the attendants instructed the passengers on emergency landing procedures. A number of passengers later reported that the aircraft safety cards proved useful in locating the nearest exit.{{Citation needed|date=January 2009}}

The flight returned to Detroit, but when the crew set the flaps to 35 degrees for landing, the aircraft stabilized in a 1,900 ft/min descent that was far too fast for landing. By applying power to the 1 and 3 engines, McCormick was able to level off the nose and reduce the descent to 700 ft/min. The aircraft touched down at 7:44 pm 1,900 ft down Runway 03R, immediately veering to the right and eventually leaving the runway surface. The first officer, Peter Whitney, applied full reverse thrust to the left engine and idled the right, straightening the aircraft's path, and eventually starting to bring the aircraft back to the runway. The aircraft stopped 8,800 ft from the runway threshold, with the nose and left gear on the runway and the right on the grass beside it.{{Citation needed|date=January 2010}} It happened that while training to convert his expertise to flying the DC-10, McCormick had practiced, in a simulator, controlling the plane with the throttles in this fashion, in the worst-case scenario of a hydraulic failure.<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> A similar technique was used in 1989 following a complete loss of hydraulic pressure on another DC-10, [[United Airlines Flight 232]].{{Citation needed|date=January 2010}}

==Investigation==
The problem that caused the accident was immediately obvious, as the cargo door was missing and had caused damage to the left horizontal stabilizer as it flew off. Investigators immediately studied the maintenance history and found that on 3 March 1972 the handlers reported that the door had not latched electrically and had to be closed manually. On 30 May McDonnell Douglas issued Service Bulletin 52-27, DC-10 SC 612, which called for the upgrading of the electrical wiring that drove the latches because "Three operators have reported failure of the electrical latch actuators to latch/unlatch the cargo doors. Latch actuator failure is attributed to an excessive voltage drop reducing the output torque to the actuator. This condition may prevent electrical latching/unlatching of the hooks."<ref name="NTSB"/> The modification was not compulsory, however, and had not been carried out on N103AA.

Investigators interviewed the ground crew at Detroit and learned that the cargo loader operating the rear door found it difficult to close. He stated that he closed the door electrically, and waited for the sound of the actuator motors to stop. When they did, he attempted to operate the locking handle, but found it very difficult to close. Adding force with his knee he was able to get the latch to lock, but noticed that the vent plug (see below) was not entirely closed. He brought this to the attention of a mechanic, who cleared the flight. The flight engineer reported that the "door ajar" warning light on his panel was not lit at any time during the taxi out or flight.<ref name="NTSB"/>

Examination of the aircraft and the cargo door, which was recovered largely intact, demonstrated that the latches had not rotated to their locked position. In their locked position, pressure on the door presses the latches further shut, and no force is transmitted into the actuator system that closes and opens them. With the latches only partially closed, forces on the door were transmitted back into the actuator, eventually overwhelming it at about 6,600 lbf. The rapid depressurization when the door broke off caused the floor above it to fail, which pulled the rudder cable to its extension limit and severed several other operating cables.

==Cause==
{{Unreferenced section|date=January 2010}}
Passenger doors on the DC-10 are of the [[plug door|plug variety]], which prevents the doors from opening while the aircraft is pressurized. The cargo door, however, is not. Due to its large area, the cargo door on the DC-10 could not be swung inside the fuselage without taking up a considerable amount of valuable cargo space. Instead, the door swung outward, allowing cargo to be stored directly behind it. The outward-opening door, in theory, allowed it to be "blown open" by the pressure inside the cargo area.

To prevent this, the DC-10 used a "[[fail safe]]" latching system held in place by "over top dead center latches", five C-shaped latches mounted on a common torque shaft that are rotated over fixed latching pins ("spools") fixed to the aircraft fuselage. Because of their shape, when the latches are in the proper position, pressure on the door does not place torque on the latches that could cause them to open, and actually further seats them on the pins. Normally the latches are opened and closed by a screw jack powered by an electric actuator motor.

Because of the under-designed cabling powering the actuator motor, it was possible for the voltage delivered to the motor to be too small to drive it under high loads. In these cases, the motor would stop turning even if the latches had not rotated over the pins. Since the operators listened for the motors to stop as an indication of their complete rotation, a failure in the drive system during operation would erroneously indicate that the door was properly latched.

To ensure this rotation had completed and the latches were in the proper position, the DC-10 cargo door also included a separate locking mechanism. The locks consisting of small pins that were slid horizontally through holes on the back of the latches, between the latch and the frame of the aircraft. When the pins were in place they mechanically prevented movement back into the open position, so even the actuator motor could no longer open them. If the latches were not in their correct positions, the pins could not enter the holes, and the operating handle on the outside of the door would remain open and visually indicate that there was a problem. Additionally, the handle moved a metal plug into a vent cut in the outer door panel; if the vent was not plugged the door would not retain pressure, eliminating any force on the door. Lastly, there was an indicator light in the cockpit that would remain on if the door was not correctly latched.

In theory, the motor failure on Flight 96 could not present a problem because the locking lever would not be able to close. However, during the investigation a McDonnell Douglas test rig demonstrated that the entire locking pin operating system was too weak, allowing the handle to be forced closed even with the pins out of the locking holes. This occurred on Flight 96, when the handler forced the handle closed with his knee. In spite of the vent not closing completely, neither the handler nor the engineer considered this to be serious. Although the vent door remained partially open, it closed enough to cause it to "blow shut", and thereby allow pressurization of the cargo hold. Although the handle did not seat the pins entirely, the small amount of motion it managed to cause was enough to press on the warning indicator switch, turning the warning light off. It was only the combination of all of these failures that allowed the accident to happen. Yet all of these indicators had a single common point of failure, the mechanical weakness of the locking system that allowed the handle to be moved.

The cabin floor failure was also a matter of poor design. All of the other portions of the cargo holds had holes cut into the cabin floor above the cargo areas. In the case of a pressure loss on either side of the floor, the air would flow through the vents and equalize the pressure, thereby eliminating any force on the floor. Only the rearmost portion of the cabin lacked these holes, and it was that portion that failed. However, because the control cables ran through the floor for the entire length of the aircraft, a failure at any point on the floor would cut controls to the tail section.

==Aftermath==
The NTSB suggested several changes to the system to ensure that the Windsor accident would not recur. These included changes to the locking mechanism to ensure it could not be forced closed, as well as venting cut into the rear cabin floor.{{Citation needed|date=January 2010}}

In response, the [[FAA]], in charge of actually implementing these recommendations, agreed with McDonnell Douglas that the additional venting would be difficult to install. Instead, they proceeded with the modification of the locking system, and additionally added a small clear window set into the bottom of the cargo door that allowed operators to directly inspect whether or not the latches were in place.{{Citation needed|date=January 2010}} Combined with the upgrades to the wiring that had already been on the books, this should prevent a repeat of the accident.{{Citation needed|date=January 2010}}

Shortly after the event, [[Dan Applegate]], Director of Product Engineering at [[Convair]], wrote a memo to [[Convair]] management pointing out several problems with the door design. McDonnell Douglas had subcontracted design and construction of the DC-10 fuselage to Convair, and Applegate had overseen its development in ways that he felt were reducing the safety of the system. In particular, he noted that the actuator system had been switched from a hydraulic system to an electrical one, which he felt was less safe. He also noted that the floor would be prone to failure if the door was lost, and this would likely sever the control cables, leading to a loss of the aircraft. Finally, he pointed out that this precise failure had already occurred in ground testing in 1970, and he concluded that such an accident was almost certain to occur again in the future.<ref name = Fielder>John Fielder, Douglas Birsch, [http://books.google.com/books?id=gBHGmwmMj30C&pg=PA4&lpg=PA4&dq=%22Applegate+memorandum%22&source=web&ots=v1rP3bvPYn&sig=V9duWkuQlS7_6CV40EDsLn6t0_E&hl=en&sa=X&oi=book_result&resnum=2&ct=result "The DC-10 Case"], SUNY Press, 1992, ISBN 0791410870</ref>

In spite of these recommendations, two years later [[Turkish Airlines Flight 981]] suffered an almost identical failure, but lost all control of the tail surfaces. The plane crashed outside [[Paris]], killing all 346 passengers and crew onboard.{{Citation needed|date=January 2010}} Investigators discovered that the upgrades had never been carried out on this airframe, although the construction logs claimed it had.{{Citation needed|date=January 2010}} One modification had been carried out, the installation of the inspection window, along with a placard beside the door controls printed in English and Turkish that informed the operators how to inspect the latches. The operator in Paris was Algerian and could not read either language, and had been instructed that as long as the locking handle closed the door was safe. He also noted that he did not have to force the handle, and investigators concluded that it had already been bent on a prior flight.{{Citation needed|date=January 2010}}

In the aftermath of that accident, the Applegate memorandum was discovered and introduced into evidence during the massive civil lawsuit that followed.{{Citation needed|date=January 2010}} Many commentators subsequently blamed the aircraft manufacturer, [[McDonnell Douglas]], and other aviation authorities, for failing to learn lessons from the Flight 96 accident.{{Citation needed|date=January 2010}} Although there had been some redesign of the DC-10 cargo door system, it had only been implemented voluntarily and haphazardly by various airlines.{{Citation needed|date=January 2010}} If the warning signs of Flight 96 had been heeded, the Turkish Airlines disaster would have been avoided.<ref name="Air Disaster">[[Macarthur Job]] (1994). ''Air Disaster Volume 1'': pp.136-144</ref><ref name = Fielder/>

A complete redesign of the entire door system followed, and no DC-10 or [[MD-11]] ever suffered a similar accident again.{{Citation needed|date=January 2010}}

N103AA's airframe was broken up at [[Phoenix Goodyear Airport]] in 2002, after being assigned to the [[FedEx]] [[McDonnell Douglas DC-10|MD-10]] program.{{Citation needed|date=May 2008}}

==See also==
* [[Flying an airplane without control surfaces]]
* [[List of notable accidents and incidents on commercial aircraft]]
* [[Uncontrolled decompression#Notable decompression accidents and incidents|List of notable decompression accidents and incidents]]
* [[Loss of control]]
* [[Turkish Airlines Flight 981]]
* [[United Airlines Flight 811]]

==References==
{{Reflist}}

==External links==
*[http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf NTSB Report]



{{Aviation accidents and incidents in 1972}}
{{Mayday NavBox}}

[[Category:Airliner accidents and incidents caused by design or manufacturing errors]]
[[Category:In-flight airliner structural failures]]
[[Category:Accidents and incidents involving the McDonnell Douglas DC-10]]
[[Category:History of Buffalo, New York]]
[[Category:1972 in the United States]]
[[Category:Aviation accidents and incidents in Canada]]
[[Category:American Airlines flights|96]]
[[Category:Aviation accidents and incidents in 1972]]

[[es:Vuelo 96 de American Airlines]]
[[fr:Vol 96 American Airlines]]
[[hu:Az American Airlines 96-os járatának balesete]]
[[nl:American Airlines-vlucht 96]]
[[ja:アメリカン航空96便貨物ドア破損事故]]
[[zh:美國航空96號班機事故]]

American-Airlines-Flug 96

2010-02-16T22:38:43Z

EditorASC: /* Investigation */ changed "incident" to "accident" See ICAO Annex 13 for correct nomenclature

{{Infobox Airliner accident
|Name = American Airlines Flight 96
|Crash image = Aaflight96dc10.png|360px
|Image caption = Artist's depiction of American Airlines Flight 96 losing its aft bulk cargo door
|Date = 12 June 1972|
|Type = Design flaw, Cargo door failure, control failure
|occurrence_type= Accident
|Site = [[Windsor, Ontario]]
|Origin = [[Los Angeles International Airport]]
|Destination = [[LaGuardia Airport]]
|Stopover = [[Detroit Metropolitan Wayne County Airport]]
|Last stopover = [[Buffalo Niagara International Airport]]
|Fatalities = 0
|Injuries = Several minor injuries
|Aircraft Type = [[McDonnell Douglas DC-10|McDonnell Douglas DC-10-10]]
|Operator = [[American Airlines]]
|tail_number = [http://aviation-safety.net/database/record.php?id=19720612-0 N103AA]
|Passengers = 56
|Crew = 11
|Survivors = 67 (All)
}}
'''American Airlines Flight 96''' was a regular [[McDonnell Douglas]] [[DC-10-10]] flight operated by [[American Airlines]]. The flight suffered a cargo door failure on 12 June 1972 while flying over [[Windsor, Ontario]]; it is thus sometimes referred to as the "Windsor incident."<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> The rapid [[Uncontrolled decompression|decompression]] in the cargo hold caused a partial collapse of the passenger compartment floor, which in turn ruptured hydraulic lines, pulled the rudder control cable to its maximum right position, and severed controls to engine number two (the tail engine) leading to serious problems operating the aircraft.<ref name="NTSB">{{cite web
| title = Aircraft Accident Report: American Airlines, Inc. McDonnell Douglas DC-10-10, N103AA. Near Windsor, Ontario, Canada. 12 June 1972.
| publisher = [[National Transportation Safety Board]]
| date = 1973-02-28
| url = http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf
| format = PDF
| accessdate = 2009-03-22 }}
</ref> In spite of [[loss of control|losing almost all control]], the pilots were able to make a safe landing at [[Detroit Metropolitan Wayne County Airport]] with no major injuries.

The cause was later traced to the door latching system, which had failed to close completely. A separate locking system was supposed to ensure this could not happen, but proved to be underdesigned. McDonnell Douglas instituted a number of minor changes to the system to avoid a repeat, but two years later [[Turkish Airlines Flight 981]]'s rear cargo door failed for exactly the same reason, causing the aircraft to lose all control and crash outside [[Paris]] with a loss of 346 passengers and crew, the deadliest air disaster to that point.

==Incident==
Flight 96 was a regularly scheduled flight from Los Angeles to [[LaGuardia Airport]] with stops in [[Detroit Metropolitan Wayne County Airport]] and [[Buffalo Niagara International Airport]]. On 12 June it was being flown by DC-10-10 N103AA. It left Los Angeles 46 minutes after its scheduled 1:30 pm departure due to passenger loading and traffic, arriving in Detroit at 6:36 pm. At Detroit the majority of the passengers disembarked, and the plane took on new passengers and cargo. Leaving Detroit the aircraft had 56 passengers and 11 crew. The flight departed at 7:20 pm, climbing to 6,000 for a hold before capturing V-554 (a [[victor airway]]), then climb to flight level 210 (21,000 ft).{{Citation needed|date=January 2010}}

At 7:25 pm while climbing through 11,750 ft, the crew heard a distinct "thud" and dirt in the cockpit flew up into their faces. Captain Bryce McCormick reported that he momentarily believed they had suffered a mid-air collision and the cockpit windows had been smashed. At the same time, the rudder pedals moved to their full-left position and the engine controls moved to idle. McCormick immediately took manual control of the aircraft, and attempted to re-apply power, finding that engines 1 and 3 would respond normally, but engine 2, in the tail, would not allow its controls to be moved. McCormick was able to level off and stabilize the speed at 250 knots, although at this speed control was very sluggish. They declared an emergency and requested routing back to Detroit.{{Citation needed|date=January 2010}}

In the cabin, the flight attendants saw a "fog" form within the cabin and immediately recognized it as a depressurization. Two crew were in the rear lounge area, and the floor under their feet partially collapsed into the cargo hold, giving them both minor injuries. In spite of this, the cabin crew immediately attempted to ensure the oxygen masks had deployed properly, but having occurred below the 14,000 ft limit, the masks had not deployed. One of the attendants obtained a walk-around oxygen bottle and called the cockpit on the intercom to inform them that the damage was in the rear of the aircraft. On instructions from the cabin, the attendants instructed the passengers on emergency landing procedures. A number of passengers later reported that the aircraft safety cards proved useful in locating the nearest exit.{{Citation needed|date=January 2009}}

The flight returned to Detroit, but when the crew set the flaps to 35 degrees for landing, the aircraft stabilized in a 1,900 ft/min descent that was far too fast for landing. By applying power to the 1 and 3 engines, McCormick was able to level off the nose and reduce the descent to 700 ft/min. The aircraft touched down at 7:44 pm 1,900 ft down Runway 03R, immediately veering to the right and eventually leaving the runway surface. The first officer, Peter Whitney, applied full reverse thrust to the left engine and idled the right, straightening the aircraft's path, and eventually starting to bring the aircraft back to the runway. The aircraft stopped 8,800 ft from the runway threshold, with the nose and left gear on the runway and the right on the grass beside it.{{Citation needed|date=January 2010}} It happened that while training to convert his expertise to flying the DC-10, McCormick had practiced, in a simulator, controlling the plane with the throttles in this fashion, in the worst-case scenario of a hydraulic failure.<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> A similar technique was used in 1989 following a complete loss of hydraulic pressure on another DC-10, [[United Airlines Flight 232]].{{Citation needed|date=January 2010}}

==Investigation==
The problem that caused the accident was immediately obvious, as the cargo door was missing and had caused damage to the left horizontal stabilizer as it flew off. Investigators immediately studied the maintenance history and found that on 3 March 1972 the handlers reported that the door had not latched electrically and had to be closed manually. On 30 May McDonnell Douglas issued Service Bulletin 52-27, DC-10 SC 612, which called for the upgrading of the electrical wiring that drove the latches because "Three operators have reported failure of the electrical latch actuators to latch/unlatch the cargo doors. Latch actuator failure is attributed to an excessive voltage drop reducing the output torque to the actuator. This condition may prevent electrical latching/unlatching of the hooks."<ref name="NTSB"/> The modification was not compulsory, however, and had not been carried out on N103AA.

Investigators interviewed the ground crew at Detroit and learned that the cargo loader operating the rear door found it difficult to close. He stated that he closed the door electrically, and waited for the sound of the actuator motors to stop. When they did, he attempted to operate the locking handle, but found it very difficult to close. Adding force with his knee he was able to get the latch to lock, but noticed that the vent plug (see below) was not entirely closed. He brought this to the attention of a mechanic, who cleared the flight. The flight engineer reported that the "door ajar" warning light on his panel was not lit at any time during the taxi out or flight.<ref name="NTSB"/>

Examination of the aircraft and the cargo door, which was recovered largely intact, demonstrated that the latches had not rotated to their locked position. In their locked position, pressure on the door presses the latches further shut, and no force is transmitted into the actuator system that closes and opens them. With the latches only partially closed, forces on the door were transmitted back into the actuator, eventually overwhelming it at about 6,600 lbf. The rapid depressurization when the door broke off caused the floor above it to fail, which pulled the rudder cable to its extension limit and severed several other operating cables.

==Cause==
{{Unreferenced section|date=January 2010}}
Passenger doors on the DC-10 are of the [[plug door|plug variety]], which prevents the doors from opening while the aircraft is pressurized. The cargo door, however, is not. Due to its large area, the cargo door on the DC-10 could not be swung inside the fuselage without taking up a considerable amount of valuable cargo space. Instead, the door swung outward, allowing cargo to be stored directly behind it. The outward-opening door, in theory, allowed it to be "blown open" by the pressure inside the cargo area.

To prevent this, the DC-10 used a "[[fail safe]]" latching system held in place by "over top dead center latches", five C-shaped latches mounted on a common torque shaft that are rotated over fixed latching pins ("spools") fixed to the aircraft fuselage. Because of their shape, when the latches are in the proper position, pressure on the door does not place torque on the latches that could cause them to open, and actually further seats them on the pins. Normally the latches are opened and closed by a screw jack powered by an electric actuator motor.

Because of the under-designed cabling powering the actuator motor, it was possible for the voltage delivered to the motor to be too small to drive it under high loads. In these cases, the motor would stop turning even if the latches had not rotated over the pins. Since the operators listened for the motors to stop as an indication of their complete rotation, a failure in the drive system during operation would erroneously indicate that the door was properly latched.

To ensure this rotation had completed and the latches were in the proper position, the DC-10 cargo door also included a separate locking mechanism. The locks consisting of small pins that were slid horizontally through holes on the back of the latches, between the latch and the frame of the aircraft. When the pins were in place they mechanically prevented movement back into the open position, so even the actuator motor could no longer open them. If the latches were not in their correct positions, the pins could not enter the holes, and the operating handle on the outside of the door would remain open and visually indicate that there was a problem. Additionally, the handle moved a metal plug into a vent cut in the outer door panel; if the vent was not plugged the door would not retain pressure, eliminating any force on the door. Lastly, there was an indicator light in the cockpit that would remain on if the door was not correctly latched.

In theory, the motor failure on Flight 96 could not present a problem because the locking lever would not be able to close. However, during the investigation a McDonnell Douglas test rig demonstrated that the entire locking pin operating system was too weak, allowing the handle to be forced closed even with the pins out of the locking holes. This occurred on Flight 96, when the handler forced the handle closed with his knee. In spite of the vent not closing completely, neither the handler nor the engineer considered this to be serious. Although the vent door remained partially open, it closed enough to cause it to "blow shut", and thereby allow pressurization of the cargo hold. Although the handle did not seat the pins entirely, the small amount of motion it managed to cause was enough to press on the warning indicator switch, turning the warning light off. It was only the combination of all of these failures that allowed the accident to happen. Yet all of these indicators had a single common point of failure, the mechanical weakness of the locking system that allowed the handle to be moved.

The cabin floor failure was also a matter of poor design. All of the other portions of the cargo holds had holes cut into the cabin floor above the cargo areas. In the case of a pressure loss on either side of the floor, the air would flow through the vents and equalize the pressure, thereby eliminating any force on the floor. Only the rearmost portion of the cabin lacked these holes, and it was that portion that failed. However, because the control cables ran through the floor for the entire length of the aircraft, a failure at any point on the floor would cut controls to the tail section.

==Aftermath==
The NTSB suggested several changes to the system to ensure that the Windsor accident would not recur. These included changes to the locking mechanism to ensure it could not be forced closed, as well as venting cut into the rear cabin floor.{{Citation needed|date=January 2010}}

In response, the [[FAA]], in charge of actually implementing these recommendations, agreed with McDonnell Douglas that the additional venting would be difficult to install. Instead, they proceeded with the modification of the locking system, and additionally added a small clear window set into the bottom of the cargo door that allowed operators to directly inspect whether or not the latches were in place.{{Citation needed|date=January 2010}} Combined with the upgrades to the wiring that had already been on the books, this should prevent a repeat of the accident.{{Citation needed|date=January 2010}}

Shortly after the event, [[Dan Applegate]], Director of Product Engineering at [[Convair]], wrote a memo to [[Convair]] management pointing out several problems with the door design. McDonnell Douglas had subcontracted design and construction of the DC-10 fuselage to Convair, and Applegate had overseen its development in ways that he felt were reducing the safety of the system. In particular, he noted that the actuator system had been switched from a hydraulic system to an electrical one, which he felt was less safe. He also noted that the floor would be prone to failure if the door was lost, and this would likely sever the control cables, leading to a loss of the aircraft. Finally, he pointed out that this precise failure had already occurred in ground testing in 1970, and he concluded that such an accident was almost certain to occur again in the future.<ref name = Fielder>John Fielder, Douglas Birsch, [http://books.google.com/books?id=gBHGmwmMj30C&pg=PA4&lpg=PA4&dq=%22Applegate+memorandum%22&source=web&ots=v1rP3bvPYn&sig=V9duWkuQlS7_6CV40EDsLn6t0_E&hl=en&sa=X&oi=book_result&resnum=2&ct=result "The DC-10 Case"], SUNY Press, 1992, ISBN 0791410870</ref>

In spite of these recommendations, two years later [[Turkish Airlines Flight 981]] suffered an almost identical failure, but lost all control of the tail surfaces. The plane crashed outside [[Paris]], killing all 346 passengers and crew onboard.{{Citation needed|date=January 2010}} Investigators discovered that the upgrades had never been carried out on this airframe, although the construction logs claimed it had.{{Citation needed|date=January 2010}} One modification had been carried out, the installation of the inspection window, along with a placard beside the door controls printed in English and Turkish that informed the operators how to inspect the latches. The operator in Paris was Algerian and could not read either language, and had been instructed that as long as the locking handle closed the door was safe. He also noted that he did not have to force the handle, and investigators concluded that it had already been bent on a prior flight.{{Citation needed|date=January 2010}}

In the aftermath of that accident, the Applegate memorandum was discovered and introduced into evidence during the massive civil lawsuit that followed.{{Citation needed|date=January 2010}} Many commentators subsequently blamed the aircraft manufacturer, [[McDonnell Douglas]], and other aviation authorities, for failing to learn lessons from the Flight 96 accident.{{Citation needed|date=January 2010}} Although there had been some redesign of the DC-10 cargo door system, it had only been implemented voluntarily and haphazardly by various airlines.{{Citation needed|date=January 2010}} If the warning signs of Flight 96 had been heeded, the Turkish Airlines disaster would have been avoided.<ref name="Air Disaster">[[Macarthur Job]] (1994). ''Air Disaster Volume 1'': pp.136-144</ref><ref name = Fielder/>

A complete redesign of the entire door system followed, and no DC-10 or [[MD-11]] ever suffered a similar accident again.{{Citation needed|date=January 2010}}

N103AA's airframe was broken up at [[Phoenix Goodyear Airport]] in 2002, after being assigned to the [[FedEx]] [[McDonnell Douglas DC-10|MD-10]] program.{{Citation needed|date=May 2008}}

==See also==
* [[Flying an airplane without control surfaces]]
* [[List of notable accidents and incidents on commercial aircraft]]
* [[Uncontrolled decompression#Notable decompression accidents and incidents|List of notable decompression accidents and incidents]]
* [[Loss of control]]
* [[Turkish Airlines Flight 981]]
* [[United Airlines Flight 811]]

==References==
{{Reflist}}

==External links==
*[http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf NTSB Report]



{{Aviation accidents and incidents in 1972}}
{{Mayday NavBox}}

[[Category:Airliner accidents and incidents caused by design or manufacturing errors]]
[[Category:In-flight airliner structural failures]]
[[Category:Accidents and incidents involving the McDonnell Douglas DC-10]]
[[Category:History of Buffalo, New York]]
[[Category:1972 in the United States]]
[[Category:Aviation accidents and incidents in Canada]]
[[Category:American Airlines flights|96]]
[[Category:Aviation accidents and incidents in 1972]]

[[es:Vuelo 96 de American Airlines]]
[[fr:Vol 96 American Airlines]]
[[hu:Az American Airlines 96-os járatának balesete]]
[[nl:American Airlines-vlucht 96]]
[[ja:アメリカン航空96便貨物ドア破損事故]]
[[zh:美國航空96號班機事故]]

American-Airlines-Flug 96

2010-02-16T22:33:03Z

EditorASC: Removed bold from "Windsor Incident," and substituted quotation marks, to help to distinguish the popular press use of "incident

{{Infobox Airliner accident
|Name = American Airlines Flight 96
|Crash image = Aaflight96dc10.png|360px
|Image caption = Artist's depiction of American Airlines Flight 96 losing its aft bulk cargo door
|Date = 12 June 1972|
|Type = Design flaw, Cargo door failure, control failure
|occurrence_type= Accident
|Site = [[Windsor, Ontario]]
|Origin = [[Los Angeles International Airport]]
|Destination = [[LaGuardia Airport]]
|Stopover = [[Detroit Metropolitan Wayne County Airport]]
|Last stopover = [[Buffalo Niagara International Airport]]
|Fatalities = 0
|Injuries = Several minor injuries
|Aircraft Type = [[McDonnell Douglas DC-10|McDonnell Douglas DC-10-10]]
|Operator = [[American Airlines]]
|tail_number = [http://aviation-safety.net/database/record.php?id=19720612-0 N103AA]
|Passengers = 56
|Crew = 11
|Survivors = 67 (All)
}}
'''American Airlines Flight 96''' was a regular [[McDonnell Douglas]] [[DC-10-10]] flight operated by [[American Airlines]]. The flight suffered a cargo door failure on 12 June 1972 while flying over [[Windsor, Ontario]]; it is thus sometimes referred to as the "Windsor incident."<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> The rapid [[Uncontrolled decompression|decompression]] in the cargo hold caused a partial collapse of the passenger compartment floor, which in turn ruptured hydraulic lines, pulled the rudder control cable to its maximum right position, and severed controls to engine number two (the tail engine) leading to serious problems operating the aircraft.<ref name="NTSB">{{cite web
| title = Aircraft Accident Report: American Airlines, Inc. McDonnell Douglas DC-10-10, N103AA. Near Windsor, Ontario, Canada. 12 June 1972.
| publisher = [[National Transportation Safety Board]]
| date = 1973-02-28
| url = http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf
| format = PDF
| accessdate = 2009-03-22 }}
</ref> In spite of [[loss of control|losing almost all control]], the pilots were able to make a safe landing at [[Detroit Metropolitan Wayne County Airport]] with no major injuries.

The cause was later traced to the door latching system, which had failed to close completely. A separate locking system was supposed to ensure this could not happen, but proved to be underdesigned. McDonnell Douglas instituted a number of minor changes to the system to avoid a repeat, but two years later [[Turkish Airlines Flight 981]]'s rear cargo door failed for exactly the same reason, causing the aircraft to lose all control and crash outside [[Paris]] with a loss of 346 passengers and crew, the deadliest air disaster to that point.

==Incident==
Flight 96 was a regularly scheduled flight from Los Angeles to [[LaGuardia Airport]] with stops in [[Detroit Metropolitan Wayne County Airport]] and [[Buffalo Niagara International Airport]]. On 12 June it was being flown by DC-10-10 N103AA. It left Los Angeles 46 minutes after its scheduled 1:30 pm departure due to passenger loading and traffic, arriving in Detroit at 6:36 pm. At Detroit the majority of the passengers disembarked, and the plane took on new passengers and cargo. Leaving Detroit the aircraft had 56 passengers and 11 crew. The flight departed at 7:20 pm, climbing to 6,000 for a hold before capturing V-554 (a [[victor airway]]), then climb to flight level 210 (21,000 ft).{{Citation needed|date=January 2010}}

At 7:25 pm while climbing through 11,750 ft, the crew heard a distinct "thud" and dirt in the cockpit flew up into their faces. Captain Bryce McCormick reported that he momentarily believed they had suffered a mid-air collision and the cockpit windows had been smashed. At the same time, the rudder pedals moved to their full-left position and the engine controls moved to idle. McCormick immediately took manual control of the aircraft, and attempted to re-apply power, finding that engines 1 and 3 would respond normally, but engine 2, in the tail, would not allow its controls to be moved. McCormick was able to level off and stabilize the speed at 250 knots, although at this speed control was very sluggish. They declared an emergency and requested routing back to Detroit.{{Citation needed|date=January 2010}}

In the cabin, the flight attendants saw a "fog" form within the cabin and immediately recognized it as a depressurization. Two crew were in the rear lounge area, and the floor under their feet partially collapsed into the cargo hold, giving them both minor injuries. In spite of this, the cabin crew immediately attempted to ensure the oxygen masks had deployed properly, but having occurred below the 14,000 ft limit, the masks had not deployed. One of the attendants obtained a walk-around oxygen bottle and called the cockpit on the intercom to inform them that the damage was in the rear of the aircraft. On instructions from the cabin, the attendants instructed the passengers on emergency landing procedures. A number of passengers later reported that the aircraft safety cards proved useful in locating the nearest exit.{{Citation needed|date=January 2009}}

The flight returned to Detroit, but when the crew set the flaps to 35 degrees for landing, the aircraft stabilized in a 1,900 ft/min descent that was far too fast for landing. By applying power to the 1 and 3 engines, McCormick was able to level off the nose and reduce the descent to 700 ft/min. The aircraft touched down at 7:44 pm 1,900 ft down Runway 03R, immediately veering to the right and eventually leaving the runway surface. The first officer, Peter Whitney, applied full reverse thrust to the left engine and idled the right, straightening the aircraft's path, and eventually starting to bring the aircraft back to the runway. The aircraft stopped 8,800 ft from the runway threshold, with the nose and left gear on the runway and the right on the grass beside it.{{Citation needed|date=January 2010}} It happened that while training to convert his expertise to flying the DC-10, McCormick had practiced, in a simulator, controlling the plane with the throttles in this fashion, in the worst-case scenario of a hydraulic failure.<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> A similar technique was used in 1989 following a complete loss of hydraulic pressure on another DC-10, [[United Airlines Flight 232]].{{Citation needed|date=January 2010}}

==Investigation==
The problem that caused the incident was immediately obvious, as the cargo door was missing and had caused damage to the left horizontal stabilizer as it flew off. Investigators immediately studied the maintenance history and found that on 3 March 1972 the handlers reported that the door had not latched electrically and had to be closed manually. On 30 May McDonnell Douglas issued Service Bulletin 52-27, DC-10 SC 612, which called for the upgrading of the electrical wiring that drove the latches because "Three operators have reported failure of the electrical latch actuators to latch/unlatch the cargo doors. Latch actuator failure is attributed to an excessive voltage drop reducing the output torque to the actuator. This condition may prevent electrical latching/unlatching of the hooks."<ref name="NTSB"/> The modification was not compulsory, however, and had not been carried out on N103AA.

Investigators interviewed the ground crew at Detroit and learned that the cargo loader operating the rear door found it difficult to close. He stated that he closed the door electrically, and waited for the sound of the actuator motors to stop. When they did, he attempted to operate the locking handle, but found it very difficult to close. Adding force with his knee he was able to get the latch to lock, but noticed that the vent plug (see below) was not entirely closed. He brought this to the attention of a mechanic, who cleared the flight. The flight engineer reported that the "door ajar" warning light on his panel was not lit at any time during the taxi out or flight.<ref name="NTSB"/>

Examination of the aircraft and the cargo door, which was recovered largely intact, demonstrated that the latches had not rotated to their locked position. In their locked position, pressure on the door presses the latches further shut, and no force is transmitted into the actuator system that closes and opens them. With the latches only partially closed, forces on the door were transmitted back into the actuator, eventually overwhelming it at about 6,600 lbf. The rapid depressurization when the door broke off caused the floor above it to fail, which pulled the rudder cable to its extension limit and severed several other operating cables.

==Cause==
{{Unreferenced section|date=January 2010}}
Passenger doors on the DC-10 are of the [[plug door|plug variety]], which prevents the doors from opening while the aircraft is pressurized. The cargo door, however, is not. Due to its large area, the cargo door on the DC-10 could not be swung inside the fuselage without taking up a considerable amount of valuable cargo space. Instead, the door swung outward, allowing cargo to be stored directly behind it. The outward-opening door, in theory, allowed it to be "blown open" by the pressure inside the cargo area.

To prevent this, the DC-10 used a "[[fail safe]]" latching system held in place by "over top dead center latches", five C-shaped latches mounted on a common torque shaft that are rotated over fixed latching pins ("spools") fixed to the aircraft fuselage. Because of their shape, when the latches are in the proper position, pressure on the door does not place torque on the latches that could cause them to open, and actually further seats them on the pins. Normally the latches are opened and closed by a screw jack powered by an electric actuator motor.

Because of the under-designed cabling powering the actuator motor, it was possible for the voltage delivered to the motor to be too small to drive it under high loads. In these cases, the motor would stop turning even if the latches had not rotated over the pins. Since the operators listened for the motors to stop as an indication of their complete rotation, a failure in the drive system during operation would erroneously indicate that the door was properly latched.

To ensure this rotation had completed and the latches were in the proper position, the DC-10 cargo door also included a separate locking mechanism. The locks consisting of small pins that were slid horizontally through holes on the back of the latches, between the latch and the frame of the aircraft. When the pins were in place they mechanically prevented movement back into the open position, so even the actuator motor could no longer open them. If the latches were not in their correct positions, the pins could not enter the holes, and the operating handle on the outside of the door would remain open and visually indicate that there was a problem. Additionally, the handle moved a metal plug into a vent cut in the outer door panel; if the vent was not plugged the door would not retain pressure, eliminating any force on the door. Lastly, there was an indicator light in the cockpit that would remain on if the door was not correctly latched.

In theory, the motor failure on Flight 96 could not present a problem because the locking lever would not be able to close. However, during the investigation a McDonnell Douglas test rig demonstrated that the entire locking pin operating system was too weak, allowing the handle to be forced closed even with the pins out of the locking holes. This occurred on Flight 96, when the handler forced the handle closed with his knee. In spite of the vent not closing completely, neither the handler nor the engineer considered this to be serious. Although the vent door remained partially open, it closed enough to cause it to "blow shut", and thereby allow pressurization of the cargo hold. Although the handle did not seat the pins entirely, the small amount of motion it managed to cause was enough to press on the warning indicator switch, turning the warning light off. It was only the combination of all of these failures that allowed the accident to happen. Yet all of these indicators had a single common point of failure, the mechanical weakness of the locking system that allowed the handle to be moved.

The cabin floor failure was also a matter of poor design. All of the other portions of the cargo holds had holes cut into the cabin floor above the cargo areas. In the case of a pressure loss on either side of the floor, the air would flow through the vents and equalize the pressure, thereby eliminating any force on the floor. Only the rearmost portion of the cabin lacked these holes, and it was that portion that failed. However, because the control cables ran through the floor for the entire length of the aircraft, a failure at any point on the floor would cut controls to the tail section.

==Aftermath==
The NTSB suggested several changes to the system to ensure that the Windsor accident would not recur. These included changes to the locking mechanism to ensure it could not be forced closed, as well as venting cut into the rear cabin floor.{{Citation needed|date=January 2010}}

In response, the [[FAA]], in charge of actually implementing these recommendations, agreed with McDonnell Douglas that the additional venting would be difficult to install. Instead, they proceeded with the modification of the locking system, and additionally added a small clear window set into the bottom of the cargo door that allowed operators to directly inspect whether or not the latches were in place.{{Citation needed|date=January 2010}} Combined with the upgrades to the wiring that had already been on the books, this should prevent a repeat of the accident.{{Citation needed|date=January 2010}}

Shortly after the event, [[Dan Applegate]], Director of Product Engineering at [[Convair]], wrote a memo to [[Convair]] management pointing out several problems with the door design. McDonnell Douglas had subcontracted design and construction of the DC-10 fuselage to Convair, and Applegate had overseen its development in ways that he felt were reducing the safety of the system. In particular, he noted that the actuator system had been switched from a hydraulic system to an electrical one, which he felt was less safe. He also noted that the floor would be prone to failure if the door was lost, and this would likely sever the control cables, leading to a loss of the aircraft. Finally, he pointed out that this precise failure had already occurred in ground testing in 1970, and he concluded that such an accident was almost certain to occur again in the future.<ref name = Fielder>John Fielder, Douglas Birsch, [http://books.google.com/books?id=gBHGmwmMj30C&pg=PA4&lpg=PA4&dq=%22Applegate+memorandum%22&source=web&ots=v1rP3bvPYn&sig=V9duWkuQlS7_6CV40EDsLn6t0_E&hl=en&sa=X&oi=book_result&resnum=2&ct=result "The DC-10 Case"], SUNY Press, 1992, ISBN 0791410870</ref>

In spite of these recommendations, two years later [[Turkish Airlines Flight 981]] suffered an almost identical failure, but lost all control of the tail surfaces. The plane crashed outside [[Paris]], killing all 346 passengers and crew onboard.{{Citation needed|date=January 2010}} Investigators discovered that the upgrades had never been carried out on this airframe, although the construction logs claimed it had.{{Citation needed|date=January 2010}} One modification had been carried out, the installation of the inspection window, along with a placard beside the door controls printed in English and Turkish that informed the operators how to inspect the latches. The operator in Paris was Algerian and could not read either language, and had been instructed that as long as the locking handle closed the door was safe. He also noted that he did not have to force the handle, and investigators concluded that it had already been bent on a prior flight.{{Citation needed|date=January 2010}}

In the aftermath of that accident, the Applegate memorandum was discovered and introduced into evidence during the massive civil lawsuit that followed.{{Citation needed|date=January 2010}} Many commentators subsequently blamed the aircraft manufacturer, [[McDonnell Douglas]], and other aviation authorities, for failing to learn lessons from the Flight 96 accident.{{Citation needed|date=January 2010}} Although there had been some redesign of the DC-10 cargo door system, it had only been implemented voluntarily and haphazardly by various airlines.{{Citation needed|date=January 2010}} If the warning signs of Flight 96 had been heeded, the Turkish Airlines disaster would have been avoided.<ref name="Air Disaster">[[Macarthur Job]] (1994). ''Air Disaster Volume 1'': pp.136-144</ref><ref name = Fielder/>

A complete redesign of the entire door system followed, and no DC-10 or [[MD-11]] ever suffered a similar accident again.{{Citation needed|date=January 2010}}

N103AA's airframe was broken up at [[Phoenix Goodyear Airport]] in 2002, after being assigned to the [[FedEx]] [[McDonnell Douglas DC-10|MD-10]] program.{{Citation needed|date=May 2008}}

==See also==
* [[Flying an airplane without control surfaces]]
* [[List of notable accidents and incidents on commercial aircraft]]
* [[Uncontrolled decompression#Notable decompression accidents and incidents|List of notable decompression accidents and incidents]]
* [[Loss of control]]
* [[Turkish Airlines Flight 981]]
* [[United Airlines Flight 811]]

==References==
{{Reflist}}

==External links==
*[http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf NTSB Report]



{{Aviation accidents and incidents in 1972}}
{{Mayday NavBox}}

[[Category:Airliner accidents and incidents caused by design or manufacturing errors]]
[[Category:In-flight airliner structural failures]]
[[Category:Accidents and incidents involving the McDonnell Douglas DC-10]]
[[Category:History of Buffalo, New York]]
[[Category:1972 in the United States]]
[[Category:Aviation accidents and incidents in Canada]]
[[Category:American Airlines flights|96]]
[[Category:Aviation accidents and incidents in 1972]]

[[es:Vuelo 96 de American Airlines]]
[[fr:Vol 96 American Airlines]]
[[hu:Az American Airlines 96-os járatának balesete]]
[[nl:American Airlines-vlucht 96]]
[[ja:アメリカン航空96便貨物ドア破損事故]]
[[zh:美國航空96號班機事故]]

American-Airlines-Flug 96

2010-02-16T22:29:03Z

EditorASC: /* Aftermath */ Changed "incident" to accident---see ICAO Annex 13

{{Infobox Airliner accident
|Name = American Airlines Flight 96
|Crash image = Aaflight96dc10.png|360px
|Image caption = Artist's depiction of American Airlines Flight 96 losing its aft bulk cargo door
|Date = 12 June 1972|
|Type = Design flaw, Cargo door failure, control failure
|occurrence_type= Accident
|Site = [[Windsor, Ontario]]
|Origin = [[Los Angeles International Airport]]
|Destination = [[LaGuardia Airport]]
|Stopover = [[Detroit Metropolitan Wayne County Airport]]
|Last stopover = [[Buffalo Niagara International Airport]]
|Fatalities = 0
|Injuries = Several minor injuries
|Aircraft Type = [[McDonnell Douglas DC-10|McDonnell Douglas DC-10-10]]
|Operator = [[American Airlines]]
|tail_number = [http://aviation-safety.net/database/record.php?id=19720612-0 N103AA]
|Passengers = 56
|Crew = 11
|Survivors = 67 (All)
}}
'''American Airlines Flight 96''' was a regular [[McDonnell Douglas]] [[DC-10-10]] flight operated by [[American Airlines]]. The flight suffered a cargo door failure on 12 June 1972 while flying over [[Windsor, Ontario]]; it is thus sometimes referred to as the '''Windsor incident'''.<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> The rapid [[Uncontrolled decompression|decompression]] in the cargo hold caused a partial collapse of the passenger compartment floor, which in turn ruptured hydraulic lines, pulled the rudder control cable to its maximum right position, and severed controls to engine number two (the tail engine) leading to serious problems operating the aircraft.<ref name="NTSB">{{cite web
| title = Aircraft Accident Report: American Airlines, Inc. McDonnell Douglas DC-10-10, N103AA. Near Windsor, Ontario, Canada. 12 June 1972.
| publisher = [[National Transportation Safety Board]]
| date = 1973-02-28
| url = http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf
| format = PDF
| accessdate = 2009-03-22 }}
</ref> In spite of [[loss of control|losing almost all control]], the pilots were able to make a safe landing at [[Detroit Metropolitan Wayne County Airport]] with no major injuries.

The cause was later traced to the door latching system, which had failed to close completely. A separate locking system was supposed to ensure this could not happen, but proved to be underdesigned. McDonnell Douglas instituted a number of minor changes to the system to avoid a repeat, but two years later [[Turkish Airlines Flight 981]]'s rear cargo door failed for exactly the same reason, causing the aircraft to lose all control and crash outside [[Paris]] with a loss of 346 passengers and crew, the deadliest air disaster to that point.

==Incident==
Flight 96 was a regularly scheduled flight from Los Angeles to [[LaGuardia Airport]] with stops in [[Detroit Metropolitan Wayne County Airport]] and [[Buffalo Niagara International Airport]]. On 12 June it was being flown by DC-10-10 N103AA. It left Los Angeles 46 minutes after its scheduled 1:30 pm departure due to passenger loading and traffic, arriving in Detroit at 6:36 pm. At Detroit the majority of the passengers disembarked, and the plane took on new passengers and cargo. Leaving Detroit the aircraft had 56 passengers and 11 crew. The flight departed at 7:20 pm, climbing to 6,000 for a hold before capturing V-554 (a [[victor airway]]), then climb to flight level 210 (21,000 ft).{{Citation needed|date=January 2010}}

At 7:25 pm while climbing through 11,750 ft, the crew heard a distinct "thud" and dirt in the cockpit flew up into their faces. Captain Bryce McCormick reported that he momentarily believed they had suffered a mid-air collision and the cockpit windows had been smashed. At the same time, the rudder pedals moved to their full-left position and the engine controls moved to idle. McCormick immediately took manual control of the aircraft, and attempted to re-apply power, finding that engines 1 and 3 would respond normally, but engine 2, in the tail, would not allow its controls to be moved. McCormick was able to level off and stabilize the speed at 250 knots, although at this speed control was very sluggish. They declared an emergency and requested routing back to Detroit.{{Citation needed|date=January 2010}}

In the cabin, the flight attendants saw a "fog" form within the cabin and immediately recognized it as a depressurization. Two crew were in the rear lounge area, and the floor under their feet partially collapsed into the cargo hold, giving them both minor injuries. In spite of this, the cabin crew immediately attempted to ensure the oxygen masks had deployed properly, but having occurred below the 14,000 ft limit, the masks had not deployed. One of the attendants obtained a walk-around oxygen bottle and called the cockpit on the intercom to inform them that the damage was in the rear of the aircraft. On instructions from the cabin, the attendants instructed the passengers on emergency landing procedures. A number of passengers later reported that the aircraft safety cards proved useful in locating the nearest exit.{{Citation needed|date=January 2009}}

The flight returned to Detroit, but when the crew set the flaps to 35 degrees for landing, the aircraft stabilized in a 1,900 ft/min descent that was far too fast for landing. By applying power to the 1 and 3 engines, McCormick was able to level off the nose and reduce the descent to 700 ft/min. The aircraft touched down at 7:44 pm 1,900 ft down Runway 03R, immediately veering to the right and eventually leaving the runway surface. The first officer, Peter Whitney, applied full reverse thrust to the left engine and idled the right, straightening the aircraft's path, and eventually starting to bring the aircraft back to the runway. The aircraft stopped 8,800 ft from the runway threshold, with the nose and left gear on the runway and the right on the grass beside it.{{Citation needed|date=January 2010}} It happened that while training to convert his expertise to flying the DC-10, McCormick had practiced, in a simulator, controlling the plane with the throttles in this fashion, in the worst-case scenario of a hydraulic failure.<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> A similar technique was used in 1989 following a complete loss of hydraulic pressure on another DC-10, [[United Airlines Flight 232]].{{Citation needed|date=January 2010}}

==Investigation==
The problem that caused the incident was immediately obvious, as the cargo door was missing and had caused damage to the left horizontal stabilizer as it flew off. Investigators immediately studied the maintenance history and found that on 3 March 1972 the handlers reported that the door had not latched electrically and had to be closed manually. On 30 May McDonnell Douglas issued Service Bulletin 52-27, DC-10 SC 612, which called for the upgrading of the electrical wiring that drove the latches because "Three operators have reported failure of the electrical latch actuators to latch/unlatch the cargo doors. Latch actuator failure is attributed to an excessive voltage drop reducing the output torque to the actuator. This condition may prevent electrical latching/unlatching of the hooks."<ref name="NTSB"/> The modification was not compulsory, however, and had not been carried out on N103AA.

Investigators interviewed the ground crew at Detroit and learned that the cargo loader operating the rear door found it difficult to close. He stated that he closed the door electrically, and waited for the sound of the actuator motors to stop. When they did, he attempted to operate the locking handle, but found it very difficult to close. Adding force with his knee he was able to get the latch to lock, but noticed that the vent plug (see below) was not entirely closed. He brought this to the attention of a mechanic, who cleared the flight. The flight engineer reported that the "door ajar" warning light on his panel was not lit at any time during the taxi out or flight.<ref name="NTSB"/>

Examination of the aircraft and the cargo door, which was recovered largely intact, demonstrated that the latches had not rotated to their locked position. In their locked position, pressure on the door presses the latches further shut, and no force is transmitted into the actuator system that closes and opens them. With the latches only partially closed, forces on the door were transmitted back into the actuator, eventually overwhelming it at about 6,600 lbf. The rapid depressurization when the door broke off caused the floor above it to fail, which pulled the rudder cable to its extension limit and severed several other operating cables.

==Cause==
{{Unreferenced section|date=January 2010}}
Passenger doors on the DC-10 are of the [[plug door|plug variety]], which prevents the doors from opening while the aircraft is pressurized. The cargo door, however, is not. Due to its large area, the cargo door on the DC-10 could not be swung inside the fuselage without taking up a considerable amount of valuable cargo space. Instead, the door swung outward, allowing cargo to be stored directly behind it. The outward-opening door, in theory, allowed it to be "blown open" by the pressure inside the cargo area.

To prevent this, the DC-10 used a "[[fail safe]]" latching system held in place by "over top dead center latches", five C-shaped latches mounted on a common torque shaft that are rotated over fixed latching pins ("spools") fixed to the aircraft fuselage. Because of their shape, when the latches are in the proper position, pressure on the door does not place torque on the latches that could cause them to open, and actually further seats them on the pins. Normally the latches are opened and closed by a screw jack powered by an electric actuator motor.

Because of the under-designed cabling powering the actuator motor, it was possible for the voltage delivered to the motor to be too small to drive it under high loads. In these cases, the motor would stop turning even if the latches had not rotated over the pins. Since the operators listened for the motors to stop as an indication of their complete rotation, a failure in the drive system during operation would erroneously indicate that the door was properly latched.

To ensure this rotation had completed and the latches were in the proper position, the DC-10 cargo door also included a separate locking mechanism. The locks consisting of small pins that were slid horizontally through holes on the back of the latches, between the latch and the frame of the aircraft. When the pins were in place they mechanically prevented movement back into the open position, so even the actuator motor could no longer open them. If the latches were not in their correct positions, the pins could not enter the holes, and the operating handle on the outside of the door would remain open and visually indicate that there was a problem. Additionally, the handle moved a metal plug into a vent cut in the outer door panel; if the vent was not plugged the door would not retain pressure, eliminating any force on the door. Lastly, there was an indicator light in the cockpit that would remain on if the door was not correctly latched.

In theory, the motor failure on Flight 96 could not present a problem because the locking lever would not be able to close. However, during the investigation a McDonnell Douglas test rig demonstrated that the entire locking pin operating system was too weak, allowing the handle to be forced closed even with the pins out of the locking holes. This occurred on Flight 96, when the handler forced the handle closed with his knee. In spite of the vent not closing completely, neither the handler nor the engineer considered this to be serious. Although the vent door remained partially open, it closed enough to cause it to "blow shut", and thereby allow pressurization of the cargo hold. Although the handle did not seat the pins entirely, the small amount of motion it managed to cause was enough to press on the warning indicator switch, turning the warning light off. It was only the combination of all of these failures that allowed the accident to happen. Yet all of these indicators had a single common point of failure, the mechanical weakness of the locking system that allowed the handle to be moved.

The cabin floor failure was also a matter of poor design. All of the other portions of the cargo holds had holes cut into the cabin floor above the cargo areas. In the case of a pressure loss on either side of the floor, the air would flow through the vents and equalize the pressure, thereby eliminating any force on the floor. Only the rearmost portion of the cabin lacked these holes, and it was that portion that failed. However, because the control cables ran through the floor for the entire length of the aircraft, a failure at any point on the floor would cut controls to the tail section.

==Aftermath==
The NTSB suggested several changes to the system to ensure that the Windsor accident would not recur. These included changes to the locking mechanism to ensure it could not be forced closed, as well as venting cut into the rear cabin floor.{{Citation needed|date=January 2010}}

In response, the [[FAA]], in charge of actually implementing these recommendations, agreed with McDonnell Douglas that the additional venting would be difficult to install. Instead, they proceeded with the modification of the locking system, and additionally added a small clear window set into the bottom of the cargo door that allowed operators to directly inspect whether or not the latches were in place.{{Citation needed|date=January 2010}} Combined with the upgrades to the wiring that had already been on the books, this should prevent a repeat of the accident.{{Citation needed|date=January 2010}}

Shortly after the event, [[Dan Applegate]], Director of Product Engineering at [[Convair]], wrote a memo to [[Convair]] management pointing out several problems with the door design. McDonnell Douglas had subcontracted design and construction of the DC-10 fuselage to Convair, and Applegate had overseen its development in ways that he felt were reducing the safety of the system. In particular, he noted that the actuator system had been switched from a hydraulic system to an electrical one, which he felt was less safe. He also noted that the floor would be prone to failure if the door was lost, and this would likely sever the control cables, leading to a loss of the aircraft. Finally, he pointed out that this precise failure had already occurred in ground testing in 1970, and he concluded that such an accident was almost certain to occur again in the future.<ref name = Fielder>John Fielder, Douglas Birsch, [http://books.google.com/books?id=gBHGmwmMj30C&pg=PA4&lpg=PA4&dq=%22Applegate+memorandum%22&source=web&ots=v1rP3bvPYn&sig=V9duWkuQlS7_6CV40EDsLn6t0_E&hl=en&sa=X&oi=book_result&resnum=2&ct=result "The DC-10 Case"], SUNY Press, 1992, ISBN 0791410870</ref>

In spite of these recommendations, two years later [[Turkish Airlines Flight 981]] suffered an almost identical failure, but lost all control of the tail surfaces. The plane crashed outside [[Paris]], killing all 346 passengers and crew onboard.{{Citation needed|date=January 2010}} Investigators discovered that the upgrades had never been carried out on this airframe, although the construction logs claimed it had.{{Citation needed|date=January 2010}} One modification had been carried out, the installation of the inspection window, along with a placard beside the door controls printed in English and Turkish that informed the operators how to inspect the latches. The operator in Paris was Algerian and could not read either language, and had been instructed that as long as the locking handle closed the door was safe. He also noted that he did not have to force the handle, and investigators concluded that it had already been bent on a prior flight.{{Citation needed|date=January 2010}}

In the aftermath of that accident, the Applegate memorandum was discovered and introduced into evidence during the massive civil lawsuit that followed.{{Citation needed|date=January 2010}} Many commentators subsequently blamed the aircraft manufacturer, [[McDonnell Douglas]], and other aviation authorities, for failing to learn lessons from the Flight 96 accident.{{Citation needed|date=January 2010}} Although there had been some redesign of the DC-10 cargo door system, it had only been implemented voluntarily and haphazardly by various airlines.{{Citation needed|date=January 2010}} If the warning signs of Flight 96 had been heeded, the Turkish Airlines disaster would have been avoided.<ref name="Air Disaster">[[Macarthur Job]] (1994). ''Air Disaster Volume 1'': pp.136-144</ref><ref name = Fielder/>

A complete redesign of the entire door system followed, and no DC-10 or [[MD-11]] ever suffered a similar accident again.{{Citation needed|date=January 2010}}

N103AA's airframe was broken up at [[Phoenix Goodyear Airport]] in 2002, after being assigned to the [[FedEx]] [[McDonnell Douglas DC-10|MD-10]] program.{{Citation needed|date=May 2008}}

==See also==
* [[Flying an airplane without control surfaces]]
* [[List of notable accidents and incidents on commercial aircraft]]
* [[Uncontrolled decompression#Notable decompression accidents and incidents|List of notable decompression accidents and incidents]]
* [[Loss of control]]
* [[Turkish Airlines Flight 981]]
* [[United Airlines Flight 811]]

==References==
{{Reflist}}

==External links==
*[http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf NTSB Report]



{{Aviation accidents and incidents in 1972}}
{{Mayday NavBox}}

[[Category:Airliner accidents and incidents caused by design or manufacturing errors]]
[[Category:In-flight airliner structural failures]]
[[Category:Accidents and incidents involving the McDonnell Douglas DC-10]]
[[Category:History of Buffalo, New York]]
[[Category:1972 in the United States]]
[[Category:Aviation accidents and incidents in Canada]]
[[Category:American Airlines flights|96]]
[[Category:Aviation accidents and incidents in 1972]]

[[es:Vuelo 96 de American Airlines]]
[[fr:Vol 96 American Airlines]]
[[hu:Az American Airlines 96-os járatának balesete]]
[[nl:American Airlines-vlucht 96]]
[[ja:アメリカン航空96便貨物ドア破損事故]]
[[zh:美國航空96號班機事故]]

American-Airlines-Flug 96

2010-02-16T22:24:37Z

EditorASC: /* Aftermath */ Changed "incident" to "accident" See ICAO Annex 13 for definitions

{{Infobox Airliner accident
|Name = American Airlines Flight 96
|Crash image = Aaflight96dc10.png|360px
|Image caption = Artist's depiction of American Airlines Flight 96 losing its aft bulk cargo door
|Date = 12 June 1972|
|Type = Design flaw, Cargo door failure, control failure
|occurrence_type= Accident
|Site = [[Windsor, Ontario]]
|Origin = [[Los Angeles International Airport]]
|Destination = [[LaGuardia Airport]]
|Stopover = [[Detroit Metropolitan Wayne County Airport]]
|Last stopover = [[Buffalo Niagara International Airport]]
|Fatalities = 0
|Injuries = Several minor injuries
|Aircraft Type = [[McDonnell Douglas DC-10|McDonnell Douglas DC-10-10]]
|Operator = [[American Airlines]]
|tail_number = [http://aviation-safety.net/database/record.php?id=19720612-0 N103AA]
|Passengers = 56
|Crew = 11
|Survivors = 67 (All)
}}
'''American Airlines Flight 96''' was a regular [[McDonnell Douglas]] [[DC-10-10]] flight operated by [[American Airlines]]. The flight suffered a cargo door failure on 12 June 1972 while flying over [[Windsor, Ontario]]; it is thus sometimes referred to as the '''Windsor incident'''.<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> The rapid [[Uncontrolled decompression|decompression]] in the cargo hold caused a partial collapse of the passenger compartment floor, which in turn ruptured hydraulic lines, pulled the rudder control cable to its maximum right position, and severed controls to engine number two (the tail engine) leading to serious problems operating the aircraft.<ref name="NTSB">{{cite web
| title = Aircraft Accident Report: American Airlines, Inc. McDonnell Douglas DC-10-10, N103AA. Near Windsor, Ontario, Canada. 12 June 1972.
| publisher = [[National Transportation Safety Board]]
| date = 1973-02-28
| url = http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf
| format = PDF
| accessdate = 2009-03-22 }}
</ref> In spite of [[loss of control|losing almost all control]], the pilots were able to make a safe landing at [[Detroit Metropolitan Wayne County Airport]] with no major injuries.

The cause was later traced to the door latching system, which had failed to close completely. A separate locking system was supposed to ensure this could not happen, but proved to be underdesigned. McDonnell Douglas instituted a number of minor changes to the system to avoid a repeat, but two years later [[Turkish Airlines Flight 981]]'s rear cargo door failed for exactly the same reason, causing the aircraft to lose all control and crash outside [[Paris]] with a loss of 346 passengers and crew, the deadliest air disaster to that point.

==Incident==
Flight 96 was a regularly scheduled flight from Los Angeles to [[LaGuardia Airport]] with stops in [[Detroit Metropolitan Wayne County Airport]] and [[Buffalo Niagara International Airport]]. On 12 June it was being flown by DC-10-10 N103AA. It left Los Angeles 46 minutes after its scheduled 1:30 pm departure due to passenger loading and traffic, arriving in Detroit at 6:36 pm. At Detroit the majority of the passengers disembarked, and the plane took on new passengers and cargo. Leaving Detroit the aircraft had 56 passengers and 11 crew. The flight departed at 7:20 pm, climbing to 6,000 for a hold before capturing V-554 (a [[victor airway]]), then climb to flight level 210 (21,000 ft).{{Citation needed|date=January 2010}}

At 7:25 pm while climbing through 11,750 ft, the crew heard a distinct "thud" and dirt in the cockpit flew up into their faces. Captain Bryce McCormick reported that he momentarily believed they had suffered a mid-air collision and the cockpit windows had been smashed. At the same time, the rudder pedals moved to their full-left position and the engine controls moved to idle. McCormick immediately took manual control of the aircraft, and attempted to re-apply power, finding that engines 1 and 3 would respond normally, but engine 2, in the tail, would not allow its controls to be moved. McCormick was able to level off and stabilize the speed at 250 knots, although at this speed control was very sluggish. They declared an emergency and requested routing back to Detroit.{{Citation needed|date=January 2010}}

In the cabin, the flight attendants saw a "fog" form within the cabin and immediately recognized it as a depressurization. Two crew were in the rear lounge area, and the floor under their feet partially collapsed into the cargo hold, giving them both minor injuries. In spite of this, the cabin crew immediately attempted to ensure the oxygen masks had deployed properly, but having occurred below the 14,000 ft limit, the masks had not deployed. One of the attendants obtained a walk-around oxygen bottle and called the cockpit on the intercom to inform them that the damage was in the rear of the aircraft. On instructions from the cabin, the attendants instructed the passengers on emergency landing procedures. A number of passengers later reported that the aircraft safety cards proved useful in locating the nearest exit.{{Citation needed|date=January 2009}}

The flight returned to Detroit, but when the crew set the flaps to 35 degrees for landing, the aircraft stabilized in a 1,900 ft/min descent that was far too fast for landing. By applying power to the 1 and 3 engines, McCormick was able to level off the nose and reduce the descent to 700 ft/min. The aircraft touched down at 7:44 pm 1,900 ft down Runway 03R, immediately veering to the right and eventually leaving the runway surface. The first officer, Peter Whitney, applied full reverse thrust to the left engine and idled the right, straightening the aircraft's path, and eventually starting to bring the aircraft back to the runway. The aircraft stopped 8,800 ft from the runway threshold, with the nose and left gear on the runway and the right on the grass beside it.{{Citation needed|date=January 2010}} It happened that while training to convert his expertise to flying the DC-10, McCormick had practiced, in a simulator, controlling the plane with the throttles in this fashion, in the worst-case scenario of a hydraulic failure.<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> A similar technique was used in 1989 following a complete loss of hydraulic pressure on another DC-10, [[United Airlines Flight 232]].{{Citation needed|date=January 2010}}

==Investigation==
The problem that caused the incident was immediately obvious, as the cargo door was missing and had caused damage to the left horizontal stabilizer as it flew off. Investigators immediately studied the maintenance history and found that on 3 March 1972 the handlers reported that the door had not latched electrically and had to be closed manually. On 30 May McDonnell Douglas issued Service Bulletin 52-27, DC-10 SC 612, which called for the upgrading of the electrical wiring that drove the latches because "Three operators have reported failure of the electrical latch actuators to latch/unlatch the cargo doors. Latch actuator failure is attributed to an excessive voltage drop reducing the output torque to the actuator. This condition may prevent electrical latching/unlatching of the hooks."<ref name="NTSB"/> The modification was not compulsory, however, and had not been carried out on N103AA.

Investigators interviewed the ground crew at Detroit and learned that the cargo loader operating the rear door found it difficult to close. He stated that he closed the door electrically, and waited for the sound of the actuator motors to stop. When they did, he attempted to operate the locking handle, but found it very difficult to close. Adding force with his knee he was able to get the latch to lock, but noticed that the vent plug (see below) was not entirely closed. He brought this to the attention of a mechanic, who cleared the flight. The flight engineer reported that the "door ajar" warning light on his panel was not lit at any time during the taxi out or flight.<ref name="NTSB"/>

Examination of the aircraft and the cargo door, which was recovered largely intact, demonstrated that the latches had not rotated to their locked position. In their locked position, pressure on the door presses the latches further shut, and no force is transmitted into the actuator system that closes and opens them. With the latches only partially closed, forces on the door were transmitted back into the actuator, eventually overwhelming it at about 6,600 lbf. The rapid depressurization when the door broke off caused the floor above it to fail, which pulled the rudder cable to its extension limit and severed several other operating cables.

==Cause==
{{Unreferenced section|date=January 2010}}
Passenger doors on the DC-10 are of the [[plug door|plug variety]], which prevents the doors from opening while the aircraft is pressurized. The cargo door, however, is not. Due to its large area, the cargo door on the DC-10 could not be swung inside the fuselage without taking up a considerable amount of valuable cargo space. Instead, the door swung outward, allowing cargo to be stored directly behind it. The outward-opening door, in theory, allowed it to be "blown open" by the pressure inside the cargo area.

To prevent this, the DC-10 used a "[[fail safe]]" latching system held in place by "over top dead center latches", five C-shaped latches mounted on a common torque shaft that are rotated over fixed latching pins ("spools") fixed to the aircraft fuselage. Because of their shape, when the latches are in the proper position, pressure on the door does not place torque on the latches that could cause them to open, and actually further seats them on the pins. Normally the latches are opened and closed by a screw jack powered by an electric actuator motor.

Because of the under-designed cabling powering the actuator motor, it was possible for the voltage delivered to the motor to be too small to drive it under high loads. In these cases, the motor would stop turning even if the latches had not rotated over the pins. Since the operators listened for the motors to stop as an indication of their complete rotation, a failure in the drive system during operation would erroneously indicate that the door was properly latched.

To ensure this rotation had completed and the latches were in the proper position, the DC-10 cargo door also included a separate locking mechanism. The locks consisting of small pins that were slid horizontally through holes on the back of the latches, between the latch and the frame of the aircraft. When the pins were in place they mechanically prevented movement back into the open position, so even the actuator motor could no longer open them. If the latches were not in their correct positions, the pins could not enter the holes, and the operating handle on the outside of the door would remain open and visually indicate that there was a problem. Additionally, the handle moved a metal plug into a vent cut in the outer door panel; if the vent was not plugged the door would not retain pressure, eliminating any force on the door. Lastly, there was an indicator light in the cockpit that would remain on if the door was not correctly latched.

In theory, the motor failure on Flight 96 could not present a problem because the locking lever would not be able to close. However, during the investigation a McDonnell Douglas test rig demonstrated that the entire locking pin operating system was too weak, allowing the handle to be forced closed even with the pins out of the locking holes. This occurred on Flight 96, when the handler forced the handle closed with his knee. In spite of the vent not closing completely, neither the handler nor the engineer considered this to be serious. Although the vent door remained partially open, it closed enough to cause it to "blow shut", and thereby allow pressurization of the cargo hold. Although the handle did not seat the pins entirely, the small amount of motion it managed to cause was enough to press on the warning indicator switch, turning the warning light off. It was only the combination of all of these failures that allowed the accident to happen. Yet all of these indicators had a single common point of failure, the mechanical weakness of the locking system that allowed the handle to be moved.

The cabin floor failure was also a matter of poor design. All of the other portions of the cargo holds had holes cut into the cabin floor above the cargo areas. In the case of a pressure loss on either side of the floor, the air would flow through the vents and equalize the pressure, thereby eliminating any force on the floor. Only the rearmost portion of the cabin lacked these holes, and it was that portion that failed. However, because the control cables ran through the floor for the entire length of the aircraft, a failure at any point on the floor would cut controls to the tail section.

==Aftermath==
The NTSB suggested several changes to the system to ensure that the Windsor accident would not recur. These included changes to the locking mechanism to ensure it could not be forced closed, as well as venting cut into the rear cabin floor.{{Citation needed|date=January 2010}}

In response, the [[FAA]], in charge of actually implementing these recommendations, agreed with McDonnell Douglas that the additional venting would be difficult to install. Instead, they proceeded with the modification of the locking system, and additionally added a small clear window set into the bottom of the cargo door that allowed operators to directly inspect whether or not the latches were in place.{{Citation needed|date=January 2010}} Combined with the upgrades to the wiring that had already been on the books, this should prevent a repeat of the accident.{{Citation needed|date=January 2010}}

Shortly after the event, [[Dan Applegate]], Director of Product Engineering at [[Convair]], wrote a memo to [[Convair]] management pointing out several problems with the door design. McDonnell Douglas had subcontracted design and construction of the DC-10 fuselage to Convair, and Applegate had overseen its development in ways that he felt were reducing the safety of the system. In particular, he noted that the actuator system had been switched from a hydraulic system to an electrical one, which he felt was less safe. He also noted that the floor would be prone to failure if the door was lost, and this would likely sever the control cables, leading to a loss of the aircraft. Finally, he pointed out that this precise failure had already occurred in ground testing in 1970, and he concluded that such an accident was almost certain to occur again in the future.<ref name = Fielder>John Fielder, Douglas Birsch, [http://books.google.com/books?id=gBHGmwmMj30C&pg=PA4&lpg=PA4&dq=%22Applegate+memorandum%22&source=web&ots=v1rP3bvPYn&sig=V9duWkuQlS7_6CV40EDsLn6t0_E&hl=en&sa=X&oi=book_result&resnum=2&ct=result "The DC-10 Case"], SUNY Press, 1992, ISBN 0791410870</ref>

In spite of these recommendations, two years later [[Turkish Airlines Flight 981]] suffered an almost identical failure, but lost all control of the tail surfaces. The plane crashed outside [[Paris]], killing all 346 passengers and crew onboard.{{Citation needed|date=January 2010}} Investigators discovered that the upgrades had never been carried out on this airframe, although the construction logs claimed it had.{{Citation needed|date=January 2010}} One modification had been carried out, the installation of the inspection window, along with a placard beside the door controls printed in English and Turkish that informed the operators how to inspect the latches. The operator in Paris was Algerian and could not read either language, and had been instructed that as long as the locking handle closed the door was safe. He also noted that he did not have to force the handle, and investigators concluded that it had already been bent on a prior flight.{{Citation needed|date=January 2010}}

In the aftermath of that accident, the Applegate memorandum was discovered and introduced into evidence during the massive civil lawsuit that followed.{{Citation needed|date=January 2010}} Many commentators subsequently blamed the aircraft manufacturer, [[McDonnell Douglas]], and other aviation authorities, for failing to learn lessons from the Flight 96 incident.{{Citation needed|date=January 2010}} Although there had been some redesign of the DC-10 cargo door system, it had only been implemented voluntarily and haphazardly by various airlines.{{Citation needed|date=January 2010}} If the warning signs of Flight 96 had been heeded, the Turkish Airlines disaster would have been avoided.<ref name="Air Disaster">[[Macarthur Job]] (1994). ''Air Disaster Volume 1'': pp.136-144</ref><ref name = Fielder/>

A complete redesign of the entire door system followed, and no DC-10 or [[MD-11]] ever suffered a similar accident again.{{Citation needed|date=January 2010}}

N103AA's airframe was broken up at [[Phoenix Goodyear Airport]] in 2002, after being assigned to the [[FedEx]] [[McDonnell Douglas DC-10|MD-10]] program.{{Citation needed|date=May 2008}}

==See also==
* [[Flying an airplane without control surfaces]]
* [[List of notable accidents and incidents on commercial aircraft]]
* [[Uncontrolled decompression#Notable decompression accidents and incidents|List of notable decompression accidents and incidents]]
* [[Loss of control]]
* [[Turkish Airlines Flight 981]]
* [[United Airlines Flight 811]]

==References==
{{Reflist}}

==External links==
*[http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf NTSB Report]



{{Aviation accidents and incidents in 1972}}
{{Mayday NavBox}}

[[Category:Airliner accidents and incidents caused by design or manufacturing errors]]
[[Category:In-flight airliner structural failures]]
[[Category:Accidents and incidents involving the McDonnell Douglas DC-10]]
[[Category:History of Buffalo, New York]]
[[Category:1972 in the United States]]
[[Category:Aviation accidents and incidents in Canada]]
[[Category:American Airlines flights|96]]
[[Category:Aviation accidents and incidents in 1972]]

[[es:Vuelo 96 de American Airlines]]
[[fr:Vol 96 American Airlines]]
[[hu:Az American Airlines 96-os járatának balesete]]
[[nl:American Airlines-vlucht 96]]
[[ja:アメリカン航空96便貨物ドア破損事故]]
[[zh:美國航空96號班機事故]]

American-Airlines-Flug 96

2010-02-16T22:20:17Z

EditorASC: /* Aftermath */ changed "incident" to "accident" Popular press language is not Wiki's guide to proper definitions

{{Infobox Airliner accident
|Name = American Airlines Flight 96
|Crash image = Aaflight96dc10.png|360px
|Image caption = Artist's depiction of American Airlines Flight 96 losing its aft bulk cargo door
|Date = 12 June 1972|
|Type = Design flaw, Cargo door failure, control failure
|occurrence_type= Accident
|Site = [[Windsor, Ontario]]
|Origin = [[Los Angeles International Airport]]
|Destination = [[LaGuardia Airport]]
|Stopover = [[Detroit Metropolitan Wayne County Airport]]
|Last stopover = [[Buffalo Niagara International Airport]]
|Fatalities = 0
|Injuries = Several minor injuries
|Aircraft Type = [[McDonnell Douglas DC-10|McDonnell Douglas DC-10-10]]
|Operator = [[American Airlines]]
|tail_number = [http://aviation-safety.net/database/record.php?id=19720612-0 N103AA]
|Passengers = 56
|Crew = 11
|Survivors = 67 (All)
}}
'''American Airlines Flight 96''' was a regular [[McDonnell Douglas]] [[DC-10-10]] flight operated by [[American Airlines]]. The flight suffered a cargo door failure on 12 June 1972 while flying over [[Windsor, Ontario]]; it is thus sometimes referred to as the '''Windsor incident'''.<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> The rapid [[Uncontrolled decompression|decompression]] in the cargo hold caused a partial collapse of the passenger compartment floor, which in turn ruptured hydraulic lines, pulled the rudder control cable to its maximum right position, and severed controls to engine number two (the tail engine) leading to serious problems operating the aircraft.<ref name="NTSB">{{cite web
| title = Aircraft Accident Report: American Airlines, Inc. McDonnell Douglas DC-10-10, N103AA. Near Windsor, Ontario, Canada. 12 June 1972.
| publisher = [[National Transportation Safety Board]]
| date = 1973-02-28
| url = http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf
| format = PDF
| accessdate = 2009-03-22 }}
</ref> In spite of [[loss of control|losing almost all control]], the pilots were able to make a safe landing at [[Detroit Metropolitan Wayne County Airport]] with no major injuries.

The cause was later traced to the door latching system, which had failed to close completely. A separate locking system was supposed to ensure this could not happen, but proved to be underdesigned. McDonnell Douglas instituted a number of minor changes to the system to avoid a repeat, but two years later [[Turkish Airlines Flight 981]]'s rear cargo door failed for exactly the same reason, causing the aircraft to lose all control and crash outside [[Paris]] with a loss of 346 passengers and crew, the deadliest air disaster to that point.

==Incident==
Flight 96 was a regularly scheduled flight from Los Angeles to [[LaGuardia Airport]] with stops in [[Detroit Metropolitan Wayne County Airport]] and [[Buffalo Niagara International Airport]]. On 12 June it was being flown by DC-10-10 N103AA. It left Los Angeles 46 minutes after its scheduled 1:30 pm departure due to passenger loading and traffic, arriving in Detroit at 6:36 pm. At Detroit the majority of the passengers disembarked, and the plane took on new passengers and cargo. Leaving Detroit the aircraft had 56 passengers and 11 crew. The flight departed at 7:20 pm, climbing to 6,000 for a hold before capturing V-554 (a [[victor airway]]), then climb to flight level 210 (21,000 ft).{{Citation needed|date=January 2010}}

At 7:25 pm while climbing through 11,750 ft, the crew heard a distinct "thud" and dirt in the cockpit flew up into their faces. Captain Bryce McCormick reported that he momentarily believed they had suffered a mid-air collision and the cockpit windows had been smashed. At the same time, the rudder pedals moved to their full-left position and the engine controls moved to idle. McCormick immediately took manual control of the aircraft, and attempted to re-apply power, finding that engines 1 and 3 would respond normally, but engine 2, in the tail, would not allow its controls to be moved. McCormick was able to level off and stabilize the speed at 250 knots, although at this speed control was very sluggish. They declared an emergency and requested routing back to Detroit.{{Citation needed|date=January 2010}}

In the cabin, the flight attendants saw a "fog" form within the cabin and immediately recognized it as a depressurization. Two crew were in the rear lounge area, and the floor under their feet partially collapsed into the cargo hold, giving them both minor injuries. In spite of this, the cabin crew immediately attempted to ensure the oxygen masks had deployed properly, but having occurred below the 14,000 ft limit, the masks had not deployed. One of the attendants obtained a walk-around oxygen bottle and called the cockpit on the intercom to inform them that the damage was in the rear of the aircraft. On instructions from the cabin, the attendants instructed the passengers on emergency landing procedures. A number of passengers later reported that the aircraft safety cards proved useful in locating the nearest exit.{{Citation needed|date=January 2009}}

The flight returned to Detroit, but when the crew set the flaps to 35 degrees for landing, the aircraft stabilized in a 1,900 ft/min descent that was far too fast for landing. By applying power to the 1 and 3 engines, McCormick was able to level off the nose and reduce the descent to 700 ft/min. The aircraft touched down at 7:44 pm 1,900 ft down Runway 03R, immediately veering to the right and eventually leaving the runway surface. The first officer, Peter Whitney, applied full reverse thrust to the left engine and idled the right, straightening the aircraft's path, and eventually starting to bring the aircraft back to the runway. The aircraft stopped 8,800 ft from the runway threshold, with the nose and left gear on the runway and the right on the grass beside it.{{Citation needed|date=January 2010}} It happened that while training to convert his expertise to flying the DC-10, McCormick had practiced, in a simulator, controlling the plane with the throttles in this fashion, in the worst-case scenario of a hydraulic failure.<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> A similar technique was used in 1989 following a complete loss of hydraulic pressure on another DC-10, [[United Airlines Flight 232]].{{Citation needed|date=January 2010}}

==Investigation==
The problem that caused the incident was immediately obvious, as the cargo door was missing and had caused damage to the left horizontal stabilizer as it flew off. Investigators immediately studied the maintenance history and found that on 3 March 1972 the handlers reported that the door had not latched electrically and had to be closed manually. On 30 May McDonnell Douglas issued Service Bulletin 52-27, DC-10 SC 612, which called for the upgrading of the electrical wiring that drove the latches because "Three operators have reported failure of the electrical latch actuators to latch/unlatch the cargo doors. Latch actuator failure is attributed to an excessive voltage drop reducing the output torque to the actuator. This condition may prevent electrical latching/unlatching of the hooks."<ref name="NTSB"/> The modification was not compulsory, however, and had not been carried out on N103AA.

Investigators interviewed the ground crew at Detroit and learned that the cargo loader operating the rear door found it difficult to close. He stated that he closed the door electrically, and waited for the sound of the actuator motors to stop. When they did, he attempted to operate the locking handle, but found it very difficult to close. Adding force with his knee he was able to get the latch to lock, but noticed that the vent plug (see below) was not entirely closed. He brought this to the attention of a mechanic, who cleared the flight. The flight engineer reported that the "door ajar" warning light on his panel was not lit at any time during the taxi out or flight.<ref name="NTSB"/>

Examination of the aircraft and the cargo door, which was recovered largely intact, demonstrated that the latches had not rotated to their locked position. In their locked position, pressure on the door presses the latches further shut, and no force is transmitted into the actuator system that closes and opens them. With the latches only partially closed, forces on the door were transmitted back into the actuator, eventually overwhelming it at about 6,600 lbf. The rapid depressurization when the door broke off caused the floor above it to fail, which pulled the rudder cable to its extension limit and severed several other operating cables.

==Cause==
{{Unreferenced section|date=January 2010}}
Passenger doors on the DC-10 are of the [[plug door|plug variety]], which prevents the doors from opening while the aircraft is pressurized. The cargo door, however, is not. Due to its large area, the cargo door on the DC-10 could not be swung inside the fuselage without taking up a considerable amount of valuable cargo space. Instead, the door swung outward, allowing cargo to be stored directly behind it. The outward-opening door, in theory, allowed it to be "blown open" by the pressure inside the cargo area.

To prevent this, the DC-10 used a "[[fail safe]]" latching system held in place by "over top dead center latches", five C-shaped latches mounted on a common torque shaft that are rotated over fixed latching pins ("spools") fixed to the aircraft fuselage. Because of their shape, when the latches are in the proper position, pressure on the door does not place torque on the latches that could cause them to open, and actually further seats them on the pins. Normally the latches are opened and closed by a screw jack powered by an electric actuator motor.

Because of the under-designed cabling powering the actuator motor, it was possible for the voltage delivered to the motor to be too small to drive it under high loads. In these cases, the motor would stop turning even if the latches had not rotated over the pins. Since the operators listened for the motors to stop as an indication of their complete rotation, a failure in the drive system during operation would erroneously indicate that the door was properly latched.

To ensure this rotation had completed and the latches were in the proper position, the DC-10 cargo door also included a separate locking mechanism. The locks consisting of small pins that were slid horizontally through holes on the back of the latches, between the latch and the frame of the aircraft. When the pins were in place they mechanically prevented movement back into the open position, so even the actuator motor could no longer open them. If the latches were not in their correct positions, the pins could not enter the holes, and the operating handle on the outside of the door would remain open and visually indicate that there was a problem. Additionally, the handle moved a metal plug into a vent cut in the outer door panel; if the vent was not plugged the door would not retain pressure, eliminating any force on the door. Lastly, there was an indicator light in the cockpit that would remain on if the door was not correctly latched.

In theory, the motor failure on Flight 96 could not present a problem because the locking lever would not be able to close. However, during the investigation a McDonnell Douglas test rig demonstrated that the entire locking pin operating system was too weak, allowing the handle to be forced closed even with the pins out of the locking holes. This occurred on Flight 96, when the handler forced the handle closed with his knee. In spite of the vent not closing completely, neither the handler nor the engineer considered this to be serious. Although the vent door remained partially open, it closed enough to cause it to "blow shut", and thereby allow pressurization of the cargo hold. Although the handle did not seat the pins entirely, the small amount of motion it managed to cause was enough to press on the warning indicator switch, turning the warning light off. It was only the combination of all of these failures that allowed the accident to happen. Yet all of these indicators had a single common point of failure, the mechanical weakness of the locking system that allowed the handle to be moved.

The cabin floor failure was also a matter of poor design. All of the other portions of the cargo holds had holes cut into the cabin floor above the cargo areas. In the case of a pressure loss on either side of the floor, the air would flow through the vents and equalize the pressure, thereby eliminating any force on the floor. Only the rearmost portion of the cabin lacked these holes, and it was that portion that failed. However, because the control cables ran through the floor for the entire length of the aircraft, a failure at any point on the floor would cut controls to the tail section.

==Aftermath==
The NTSB suggested several changes to the system to ensure that the Windsor accident would not recur. These included changes to the locking mechanism to ensure it could not be forced closed, as well as venting cut into the rear cabin floor.{{Citation needed|date=January 2010}}

In response, the [[FAA]], in charge of actually implementing these recommendations, agreed with McDonnell Douglas that the additional venting would be difficult to install. Instead, they proceeded with the modification of the locking system, and additionally added a small clear window set into the bottom of the cargo door that allowed operators to directly inspect whether or not the latches were in place.{{Citation needed|date=January 2010}} Combined with the upgrades to the wiring that had already been on the books, this should prevent a repeat of the accident.{{Citation needed|date=January 2010}}

Shortly after the event, [[Dan Applegate]], Director of Product Engineering at [[Convair]], wrote a memo to [[Convair]] management pointing out several problems with the door design. McDonnell Douglas had subcontracted design and construction of the DC-10 fuselage to Convair, and Applegate had overseen its development in ways that he felt were reducing the safety of the system. In particular, he noted that the actuator system had been switched from a hydraulic system to an electrical one, which he felt was less safe. He also noted that the floor would be prone to failure if the door was lost, and this would likely sever the control cables, leading to a loss of the aircraft. Finally, he pointed out that this precise failure had already occurred in ground testing in 1970, and he concluded that such an incident was almost certain to occur again in the future.<ref name = Fielder>John Fielder, Douglas Birsch, [http://books.google.com/books?id=gBHGmwmMj30C&pg=PA4&lpg=PA4&dq=%22Applegate+memorandum%22&source=web&ots=v1rP3bvPYn&sig=V9duWkuQlS7_6CV40EDsLn6t0_E&hl=en&sa=X&oi=book_result&resnum=2&ct=result "The DC-10 Case"], SUNY Press, 1992, ISBN 0791410870</ref>

In spite of these recommendations, two years later [[Turkish Airlines Flight 981]] suffered an almost identical failure, but lost all control of the tail surfaces. The plane crashed outside [[Paris]], killing all 346 passengers and crew onboard.{{Citation needed|date=January 2010}} Investigators discovered that the upgrades had never been carried out on this airframe, although the construction logs claimed it had.{{Citation needed|date=January 2010}} One modification had been carried out, the installation of the inspection window, along with a placard beside the door controls printed in English and Turkish that informed the operators how to inspect the latches. The operator in Paris was Algerian and could not read either language, and had been instructed that as long as the locking handle closed the door was safe. He also noted that he did not have to force the handle, and investigators concluded that it had already been bent on a prior flight.{{Citation needed|date=January 2010}}

In the aftermath of that accident, the Applegate memorandum was discovered and introduced into evidence during the massive civil lawsuit that followed.{{Citation needed|date=January 2010}} Many commentators subsequently blamed the aircraft manufacturer, [[McDonnell Douglas]], and other aviation authorities, for failing to learn lessons from the Flight 96 incident.{{Citation needed|date=January 2010}} Although there had been some redesign of the DC-10 cargo door system, it had only been implemented voluntarily and haphazardly by various airlines.{{Citation needed|date=January 2010}} If the warning signs of Flight 96 had been heeded, the Turkish Airlines disaster would have been avoided.<ref name="Air Disaster">[[Macarthur Job]] (1994). ''Air Disaster Volume 1'': pp.136-144</ref><ref name = Fielder/>

A complete redesign of the entire door system followed, and no DC-10 or [[MD-11]] ever suffered a similar incident again.{{Citation needed|date=January 2010}}

N103AA's airframe was broken up at [[Phoenix Goodyear Airport]] in 2002, after being assigned to the [[FedEx]] [[McDonnell Douglas DC-10|MD-10]] program.{{Citation needed|date=May 2008}}

==See also==
* [[Flying an airplane without control surfaces]]
* [[List of notable accidents and incidents on commercial aircraft]]
* [[Uncontrolled decompression#Notable decompression accidents and incidents|List of notable decompression accidents and incidents]]
* [[Loss of control]]
* [[Turkish Airlines Flight 981]]
* [[United Airlines Flight 811]]

==References==
{{Reflist}}

==External links==
*[http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf NTSB Report]



{{Aviation accidents and incidents in 1972}}
{{Mayday NavBox}}

[[Category:Airliner accidents and incidents caused by design or manufacturing errors]]
[[Category:In-flight airliner structural failures]]
[[Category:Accidents and incidents involving the McDonnell Douglas DC-10]]
[[Category:History of Buffalo, New York]]
[[Category:1972 in the United States]]
[[Category:Aviation accidents and incidents in Canada]]
[[Category:American Airlines flights|96]]
[[Category:Aviation accidents and incidents in 1972]]

[[es:Vuelo 96 de American Airlines]]
[[fr:Vol 96 American Airlines]]
[[hu:Az American Airlines 96-os járatának balesete]]
[[nl:American Airlines-vlucht 96]]
[[ja:アメリカン航空96便貨物ドア破損事故]]
[[zh:美國航空96號班機事故]]

American-Airlines-Flug 96

2010-02-16T22:18:32Z

EditorASC: /* Aftermath */ Changed "incident" to "accident," as that is the correct aviation nomenclature. See ICAO Annex 13, for proper definitions

{{Infobox Airliner accident
|Name = American Airlines Flight 96
|Crash image = Aaflight96dc10.png|360px
|Image caption = Artist's depiction of American Airlines Flight 96 losing its aft bulk cargo door
|Date = 12 June 1972|
|Type = Design flaw, Cargo door failure, control failure
|occurrence_type= Accident
|Site = [[Windsor, Ontario]]
|Origin = [[Los Angeles International Airport]]
|Destination = [[LaGuardia Airport]]
|Stopover = [[Detroit Metropolitan Wayne County Airport]]
|Last stopover = [[Buffalo Niagara International Airport]]
|Fatalities = 0
|Injuries = Several minor injuries
|Aircraft Type = [[McDonnell Douglas DC-10|McDonnell Douglas DC-10-10]]
|Operator = [[American Airlines]]
|tail_number = [http://aviation-safety.net/database/record.php?id=19720612-0 N103AA]
|Passengers = 56
|Crew = 11
|Survivors = 67 (All)
}}
'''American Airlines Flight 96''' was a regular [[McDonnell Douglas]] [[DC-10-10]] flight operated by [[American Airlines]]. The flight suffered a cargo door failure on 12 June 1972 while flying over [[Windsor, Ontario]]; it is thus sometimes referred to as the '''Windsor incident'''.<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> The rapid [[Uncontrolled decompression|decompression]] in the cargo hold caused a partial collapse of the passenger compartment floor, which in turn ruptured hydraulic lines, pulled the rudder control cable to its maximum right position, and severed controls to engine number two (the tail engine) leading to serious problems operating the aircraft.<ref name="NTSB">{{cite web
| title = Aircraft Accident Report: American Airlines, Inc. McDonnell Douglas DC-10-10, N103AA. Near Windsor, Ontario, Canada. 12 June 1972.
| publisher = [[National Transportation Safety Board]]
| date = 1973-02-28
| url = http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf
| format = PDF
| accessdate = 2009-03-22 }}
</ref> In spite of [[loss of control|losing almost all control]], the pilots were able to make a safe landing at [[Detroit Metropolitan Wayne County Airport]] with no major injuries.

The cause was later traced to the door latching system, which had failed to close completely. A separate locking system was supposed to ensure this could not happen, but proved to be underdesigned. McDonnell Douglas instituted a number of minor changes to the system to avoid a repeat, but two years later [[Turkish Airlines Flight 981]]'s rear cargo door failed for exactly the same reason, causing the aircraft to lose all control and crash outside [[Paris]] with a loss of 346 passengers and crew, the deadliest air disaster to that point.

==Incident==
Flight 96 was a regularly scheduled flight from Los Angeles to [[LaGuardia Airport]] with stops in [[Detroit Metropolitan Wayne County Airport]] and [[Buffalo Niagara International Airport]]. On 12 June it was being flown by DC-10-10 N103AA. It left Los Angeles 46 minutes after its scheduled 1:30 pm departure due to passenger loading and traffic, arriving in Detroit at 6:36 pm. At Detroit the majority of the passengers disembarked, and the plane took on new passengers and cargo. Leaving Detroit the aircraft had 56 passengers and 11 crew. The flight departed at 7:20 pm, climbing to 6,000 for a hold before capturing V-554 (a [[victor airway]]), then climb to flight level 210 (21,000 ft).{{Citation needed|date=January 2010}}

At 7:25 pm while climbing through 11,750 ft, the crew heard a distinct "thud" and dirt in the cockpit flew up into their faces. Captain Bryce McCormick reported that he momentarily believed they had suffered a mid-air collision and the cockpit windows had been smashed. At the same time, the rudder pedals moved to their full-left position and the engine controls moved to idle. McCormick immediately took manual control of the aircraft, and attempted to re-apply power, finding that engines 1 and 3 would respond normally, but engine 2, in the tail, would not allow its controls to be moved. McCormick was able to level off and stabilize the speed at 250 knots, although at this speed control was very sluggish. They declared an emergency and requested routing back to Detroit.{{Citation needed|date=January 2010}}

In the cabin, the flight attendants saw a "fog" form within the cabin and immediately recognized it as a depressurization. Two crew were in the rear lounge area, and the floor under their feet partially collapsed into the cargo hold, giving them both minor injuries. In spite of this, the cabin crew immediately attempted to ensure the oxygen masks had deployed properly, but having occurred below the 14,000 ft limit, the masks had not deployed. One of the attendants obtained a walk-around oxygen bottle and called the cockpit on the intercom to inform them that the damage was in the rear of the aircraft. On instructions from the cabin, the attendants instructed the passengers on emergency landing procedures. A number of passengers later reported that the aircraft safety cards proved useful in locating the nearest exit.{{Citation needed|date=January 2009}}

The flight returned to Detroit, but when the crew set the flaps to 35 degrees for landing, the aircraft stabilized in a 1,900 ft/min descent that was far too fast for landing. By applying power to the 1 and 3 engines, McCormick was able to level off the nose and reduce the descent to 700 ft/min. The aircraft touched down at 7:44 pm 1,900 ft down Runway 03R, immediately veering to the right and eventually leaving the runway surface. The first officer, Peter Whitney, applied full reverse thrust to the left engine and idled the right, straightening the aircraft's path, and eventually starting to bring the aircraft back to the runway. The aircraft stopped 8,800 ft from the runway threshold, with the nose and left gear on the runway and the right on the grass beside it.{{Citation needed|date=January 2010}} It happened that while training to convert his expertise to flying the DC-10, McCormick had practiced, in a simulator, controlling the plane with the throttles in this fashion, in the worst-case scenario of a hydraulic failure.<ref name="Black Box">Nicholas Faith (1996, 1998). ''Black Box'': pp.157-158</ref> A similar technique was used in 1989 following a complete loss of hydraulic pressure on another DC-10, [[United Airlines Flight 232]].{{Citation needed|date=January 2010}}

==Investigation==
The problem that caused the incident was immediately obvious, as the cargo door was missing and had caused damage to the left horizontal stabilizer as it flew off. Investigators immediately studied the maintenance history and found that on 3 March 1972 the handlers reported that the door had not latched electrically and had to be closed manually. On 30 May McDonnell Douglas issued Service Bulletin 52-27, DC-10 SC 612, which called for the upgrading of the electrical wiring that drove the latches because "Three operators have reported failure of the electrical latch actuators to latch/unlatch the cargo doors. Latch actuator failure is attributed to an excessive voltage drop reducing the output torque to the actuator. This condition may prevent electrical latching/unlatching of the hooks."<ref name="NTSB"/> The modification was not compulsory, however, and had not been carried out on N103AA.

Investigators interviewed the ground crew at Detroit and learned that the cargo loader operating the rear door found it difficult to close. He stated that he closed the door electrically, and waited for the sound of the actuator motors to stop. When they did, he attempted to operate the locking handle, but found it very difficult to close. Adding force with his knee he was able to get the latch to lock, but noticed that the vent plug (see below) was not entirely closed. He brought this to the attention of a mechanic, who cleared the flight. The flight engineer reported that the "door ajar" warning light on his panel was not lit at any time during the taxi out or flight.<ref name="NTSB"/>

Examination of the aircraft and the cargo door, which was recovered largely intact, demonstrated that the latches had not rotated to their locked position. In their locked position, pressure on the door presses the latches further shut, and no force is transmitted into the actuator system that closes and opens them. With the latches only partially closed, forces on the door were transmitted back into the actuator, eventually overwhelming it at about 6,600 lbf. The rapid depressurization when the door broke off caused the floor above it to fail, which pulled the rudder cable to its extension limit and severed several other operating cables.

==Cause==
{{Unreferenced section|date=January 2010}}
Passenger doors on the DC-10 are of the [[plug door|plug variety]], which prevents the doors from opening while the aircraft is pressurized. The cargo door, however, is not. Due to its large area, the cargo door on the DC-10 could not be swung inside the fuselage without taking up a considerable amount of valuable cargo space. Instead, the door swung outward, allowing cargo to be stored directly behind it. The outward-opening door, in theory, allowed it to be "blown open" by the pressure inside the cargo area.

To prevent this, the DC-10 used a "[[fail safe]]" latching system held in place by "over top dead center latches", five C-shaped latches mounted on a common torque shaft that are rotated over fixed latching pins ("spools") fixed to the aircraft fuselage. Because of their shape, when the latches are in the proper position, pressure on the door does not place torque on the latches that could cause them to open, and actually further seats them on the pins. Normally the latches are opened and closed by a screw jack powered by an electric actuator motor.

Because of the under-designed cabling powering the actuator motor, it was possible for the voltage delivered to the motor to be too small to drive it under high loads. In these cases, the motor would stop turning even if the latches had not rotated over the pins. Since the operators listened for the motors to stop as an indication of their complete rotation, a failure in the drive system during operation would erroneously indicate that the door was properly latched.

To ensure this rotation had completed and the latches were in the proper position, the DC-10 cargo door also included a separate locking mechanism. The locks consisting of small pins that were slid horizontally through holes on the back of the latches, between the latch and the frame of the aircraft. When the pins were in place they mechanically prevented movement back into the open position, so even the actuator motor could no longer open them. If the latches were not in their correct positions, the pins could not enter the holes, and the operating handle on the outside of the door would remain open and visually indicate that there was a problem. Additionally, the handle moved a metal plug into a vent cut in the outer door panel; if the vent was not plugged the door would not retain pressure, eliminating any force on the door. Lastly, there was an indicator light in the cockpit that would remain on if the door was not correctly latched.

In theory, the motor failure on Flight 96 could not present a problem because the locking lever would not be able to close. However, during the investigation a McDonnell Douglas test rig demonstrated that the entire locking pin operating system was too weak, allowing the handle to be forced closed even with the pins out of the locking holes. This occurred on Flight 96, when the handler forced the handle closed with his knee. In spite of the vent not closing completely, neither the handler nor the engineer considered this to be serious. Although the vent door remained partially open, it closed enough to cause it to "blow shut", and thereby allow pressurization of the cargo hold. Although the handle did not seat the pins entirely, the small amount of motion it managed to cause was enough to press on the warning indicator switch, turning the warning light off. It was only the combination of all of these failures that allowed the accident to happen. Yet all of these indicators had a single common point of failure, the mechanical weakness of the locking system that allowed the handle to be moved.

The cabin floor failure was also a matter of poor design. All of the other portions of the cargo holds had holes cut into the cabin floor above the cargo areas. In the case of a pressure loss on either side of the floor, the air would flow through the vents and equalize the pressure, thereby eliminating any force on the floor. Only the rearmost portion of the cabin lacked these holes, and it was that portion that failed. However, because the control cables ran through the floor for the entire length of the aircraft, a failure at any point on the floor would cut controls to the tail section.

==Aftermath==
The NTSB suggested several changes to the system to ensure that the Windsor accident would not recur. These included changes to the locking mechanism to ensure it could not be forced closed, as well as venting cut into the rear cabin floor.{{Citation needed|date=January 2010}}

In response, the [[FAA]], in charge of actually implementing these recommendations, agreed with McDonnell Douglas that the additional venting would be difficult to install. Instead, they proceeded with the modification of the locking system, and additionally added a small clear window set into the bottom of the cargo door that allowed operators to directly inspect whether or not the latches were in place.{{Citation needed|date=January 2010}} Combined with the upgrades to the wiring that had already been on the books, this should prevent a repeat of the incident.{{Citation needed|date=January 2010}}

Shortly after the event, [[Dan Applegate]], Director of Product Engineering at [[Convair]], wrote a memo to [[Convair]] management pointing out several problems with the door design. McDonnell Douglas had subcontracted design and construction of the DC-10 fuselage to Convair, and Applegate had overseen its development in ways that he felt were reducing the safety of the system. In particular, he noted that the actuator system had been switched from a hydraulic system to an electrical one, which he felt was less safe. He also noted that the floor would be prone to failure if the door was lost, and this would likely sever the control cables, leading to a loss of the aircraft. Finally, he pointed out that this precise failure had already occurred in ground testing in 1970, and he concluded that such an incident was almost certain to occur again in the future.<ref name = Fielder>John Fielder, Douglas Birsch, [http://books.google.com/books?id=gBHGmwmMj30C&pg=PA4&lpg=PA4&dq=%22Applegate+memorandum%22&source=web&ots=v1rP3bvPYn&sig=V9duWkuQlS7_6CV40EDsLn6t0_E&hl=en&sa=X&oi=book_result&resnum=2&ct=result "The DC-10 Case"], SUNY Press, 1992, ISBN 0791410870</ref>

In spite of these recommendations, two years later [[Turkish Airlines Flight 981]] suffered an almost identical failure, but lost all control of the tail surfaces. The plane crashed outside [[Paris]], killing all 346 passengers and crew onboard.{{Citation needed|date=January 2010}} Investigators discovered that the upgrades had never been carried out on this airframe, although the construction logs claimed it had.{{Citation needed|date=January 2010}} One modification had been carried out, the installation of the inspection window, along with a placard beside the door controls printed in English and Turkish that informed the operators how to inspect the latches. The operator in Paris was Algerian and could not read either language, and had been instructed that as long as the locking handle closed the door was safe. He also noted that he did not have to force the handle, and investigators concluded that it had already been bent on a prior flight.{{Citation needed|date=January 2010}}

In the aftermath of that accident, the Applegate memorandum was discovered and introduced into evidence during the massive civil lawsuit that followed.{{Citation needed|date=January 2010}} Many commentators subsequently blamed the aircraft manufacturer, [[McDonnell Douglas]], and other aviation authorities, for failing to learn lessons from the Flight 96 incident.{{Citation needed|date=January 2010}} Although there had been some redesign of the DC-10 cargo door system, it had only been implemented voluntarily and haphazardly by various airlines.{{Citation needed|date=January 2010}} If the warning signs of Flight 96 had been heeded, the Turkish Airlines disaster would have been avoided.<ref name="Air Disaster">[[Macarthur Job]] (1994). ''Air Disaster Volume 1'': pp.136-144</ref><ref name = Fielder/>

A complete redesign of the entire door system followed, and no DC-10 or [[MD-11]] ever suffered a similar incident again.{{Citation needed|date=January 2010}}

N103AA's airframe was broken up at [[Phoenix Goodyear Airport]] in 2002, after being assigned to the [[FedEx]] [[McDonnell Douglas DC-10|MD-10]] program.{{Citation needed|date=May 2008}}

==See also==
* [[Flying an airplane without control surfaces]]
* [[List of notable accidents and incidents on commercial aircraft]]
* [[Uncontrolled decompression#Notable decompression accidents and incidents|List of notable decompression accidents and incidents]]
* [[Loss of control]]
* [[Turkish Airlines Flight 981]]
* [[United Airlines Flight 811]]

==References==
{{Reflist}}

==External links==
*[http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR73-02.pdf NTSB Report]



{{Aviation accidents and incidents in 1972}}
{{Mayday NavBox}}

[[Category:Airliner accidents and incidents caused by design or manufacturing errors]]
[[Category:In-flight airliner structural failures]]
[[Category:Accidents and incidents involving the McDonnell Douglas DC-10]]
[[Category:History of Buffalo, New York]]
[[Category:1972 in the United States]]
[[Category:Aviation accidents and incidents in Canada]]
[[Category:American Airlines flights|96]]
[[Category:Aviation accidents and incidents in 1972]]

[[es:Vuelo 96 de American Airlines]]
[[fr:Vol 96 American Airlines]]
[[hu:Az American Airlines 96-os járatának balesete]]
[[nl:American Airlines-vlucht 96]]
[[ja:アメリカン航空96便貨物ドア破損事故]]
[[zh:美國航空96號班機事故]]

Beschuss des Airbus A300 OO-DLL der European Air Transport

2009-06-17T20:31:16Z

EditorASC: /* Awards and aftermath */ Removed Engine Photo because it was a Hoax.

{{Infobox Airliner accident|name=European Air Transport OO-DLL|
Date= {{start-date|22 November 2003}}|
Type=Missile attack, loss of flight controls|
Site=[[Baghdad International Airport]], [[Baghdad]], [[Iraq]]|
Fatalities= 0|
Injuries= 0|
Crash image=DHL Airbus A300B4-203F, BIAP 7.jpg|
Aircraft Type=Airbus [[Airbus A300|A300]]B4-203F|
Operator=[[European Air Transport]] ("DHL")|
Tail Number={{Airreg|OO|DLL}}|
Passengers=0|
Crew=3|
Survivors =3 (all)|
}}
On 22 November 2003, shortly after takeoff from [[Baghdad]], [[Iraq]], an [[Airbus A300]] [[cargo plane]] owned by [[European Air Transport]] ("DHL") was struck on the left wing tip by a [[Surface-to-Air Missile|surface-to-air missile]]. Severe wing damage resulted in a fire and [[loss of control|complete loss]] of [[hydraulic]] flight control systems. Because outboard left wing fuel tank 1A was full at takeoff, there was no fuel-air vapour explosion. Liquid jet fuel dropped away as 1A disintegrated. Inboard fuel tank 1 was pierced and leaking.

Returning to Baghdad, the 3-person crew made an unprecedented injury-free landing of the crippled aircraft, using differential engine thrust as the only pilot input.

Paris Match Reporter Claudine Vernier-Palliez accompanied a [[Fedayeen]] commando unit on their strike mission against the DHL aircraft. [http://www.iasa-intl.com/folders/belfast/241103/index.html (Her report translated here.)]

Sara Daniel, a French weekly newsmagazine journalist claimed receipt, from an unknown source, of a video that showed insurgents, faces concealed, firing a missile at the A300. Daniel was researching a feature about Iraqi resistance groups but she disclaimed any specific knowledge of the people who carried out the attack.

==Destination and crew==
The aircraft took off from [[Baghdad International Airport]] en route to [[Bahrain International Airport]] at 06:30 [[UTC]] with an experienced crew of three: two Belgians, Captain Eric Gennotte and First Officer Steeve Michielsen, and a Scot, [[flight engineer]] Mario Rofail. 

==Moments following the strike==

To reduce exposure to ground attack, the aircraft was executing a rapid climbout. At about 8,000 feet (2,450 metres), a [[9K34 Strela-3]] (SA-14 Gremlin) surface-to-air missile struck the left wing tip. The warhead damaged trailing edge surfaces and structure and caused a fire. All three hydraulic systems lost pressure and flight controls were disabled. The aircraft pitched rapidly up and down in a roller-coaster [[phugoid]], oscillating between a nose-up and a nose-down position, trying to re-establish the [[angle of attack]] from which it was disturbed.

As in the case of the 1989 [[United Airlines Flight 232]] disaster in the USA, Captain Gennotte could only use thrust to modify pitch, speed and altitude and vary throttles asymmetrically to control yaw and turn the aircraft. Flight engineer Mario Rofail executed a [[Undercarriage#Emergency_extension_systems|gravity drop]] to extend the [[landing gear]], a procedure normally accomplished with hydraulic power. Early deployment of the gear was critical to a safe outcome because increased drag helped reduce speed and stabilize the Airbus.

In about 10 minutes of experimentation, the crew learned to manage turns, climbs and descents. After a meandering trajectory, they executed a right turn and initiated a descent path to [[Baghdad International Airport]].

==Final approach and emergency landing==
[[Image:DHL Iraq missile 3.jpg|thumb|left|Reverse thrust]]
[[Image:DHL Airbus A300B4-203F, BIAP.jpg|thumb|Left wing damage]]

Because of left wing damage and fuel loss, Rofail had to monitor the engine closely. If fuel flow was lost from the left side, the flight engineer would have to feed fuel from a right tank without losing thrust. Crew survival was dependent on accurate power control of each jet engine.

Gennotte and Michielsen set up for a final approach to runway 33R. Because the aircraft drifted to the right, away from the intended course, Gennotte decided to use the shorter 33L runway. Visibility was excellent and the pilots managed a controlled descent. They knew that, counter-intuitively, they could not retard throttles before touchdown without risking the nose or a wing smashing disastrously into the ground.

At about 400 feet (120 meters), surface-generated turbulence upset the aircraft balance and the right wing dipped. With thrust adjustments, the roll was controlled but the aircraft touched down off the runway centerline. Rofail immediately deployed full [[thrust reverser|reverse thrust]] but the Airbus veered off the paved runway. Running through rough soft ground, throwing up a huge plume of sand and dragging a razor wire barrier, the aircraft stopped after about 1,000 meters.

The crew exited down the left emergency slide. Fearing an explosion, the crew started to move away from the crash site, but emergency US Air Force ground personnel stopped them from doing so as there were buried explosives (mines) meant for use against [[Saddam Hussein]]'s forces in [[Operation Iraq Freedom]] that had not been cleared. The crew was later safely evacuated from the runway.

==Awards and aftermath==

The [http://www.gapan.org/Awards/06hgb.htm Guild of Air Pilots and Air Navigators] (founded 1929) jointly honoured crewmembers with the Gordon-Burge Memorial Award. This is awarded to flight crew whose action contributed outstandingly by saving their aircraft or passengers, or made a significant contribution to future air safety. This annual award is made only if a nomination is considered to be of significant merit.

[http://www.flightsafety.org/citations/dhl_cit.html Flight Safety Foundation Professionalism Award in Flight Safety] was presented to the crewmembers for their “extraordinary piloting skills in flying their aircraft to a safe landing after a missile strike following takeoff from Baghdad, Iraq.”

In May 2006, Captain Eric Gennotte, together with Armand Jacob, an Airbus experimental test pilot, gave a presentation to the Toulouse branch of the Royal Aeronautical Society titled “Landing an A300 Successfully Without Flight Controls”.

In addition to severe wing and undercarriage damage, both jet engines suffered ruinous abuse by ingesting debris. The already aging aircraft has not flown again.

The incident became widely discussed. For Mario Rofail, the [[flight engineer]], it was a point on which to retire.

==See also==
{{commonscat|Baghdad DHL Airbus A300 OO-DLL incident 2003}}
* [[United Airlines Flight 232]]
* [[Japan Airlines Flight 123]]
* [[Flying an airplane without control surfaces]]
* [[Loss of control]]
* [[CAMPS]]
* [[Flight Guard]]
* [[Northrop Grumman Guardian]]

==References==
{{Nofootnotes|date=August 2008}}
* [http://www.flightsafety.org/citations/dhl_cit.html Flight Safety Foundation Award Citation]
* [http://www.casa.gov.au/fsa/2004/dec/22-24.pdf Australian Government Civil Aviation Safety Authority]
* [http://www.asasi.org/2004_PPTs/Malinge_Airbus%20Bagdhad_ISASI04_PPT.pdf Australian Society of Air Safety Investigators]
* Aviation Week and Space Technology, 12/08/03
*[[Mayday (TV series)|Mayday]] (also known as ''Air Emergency'' and ''Air Crash Investigation''), [[List of Mayday episodes#Season 3|Season 3, Episode 2: Attack Over Baghdad]]

==External links==
* {{ASN accident|id=20031122-0|type=Criminal Occurrence}}
* [http://hawker.smugmug.com/gallery/58908#2047837 Hawker's gallery of the incident]
* [http://www.smh.com.au/articles/2003/11/22/1069027377782.html Agence France-Presse article about the incident]

{{Mayday NavBox}}

[[Category:Aviation accidents and incidents in Iraq]]
[[Category:Airliner shootdowns]]
[[Category:Aviation accidents and incidents in 2003|Baghdad DHL shootdown incident]]
[[Category:2003 in Iraq|Baghdad DHL shootdown incident]]
[[Category:DHL]]

[[fr:Attaque d'un vol DHL en 2003 à Bagdad]]
[[nl:Aanval op DHL-vliegtuig bij Bagdad]]
[[ja:DHL貨物便撃墜事故]]
[[zh:DHL貨機巴格達遇襲事件]]

Colgan-Air-Flug 3407

2009-02-14T08:55:02Z

EditorASC: /* Crash */ Changed "incident" to "crash."

{{current|date=February 2009}}
{{Infobox Airliner accident
| name = Colgan Air Flight 3407
| image =
| caption = The plane burns after it crashed into a house in Clarence Center, N.Y.,Thursday Feb. 12, 2009.
| Date = February 12, 2009
| Type = Under Investigation
| Site = [[Clarence Center, New York|Clarence Center]], [[New York]], [[USA]]
| Fatalities = 50 (1 on ground)
| Injuries = 4 (all on the ground)
| Aircraft Type = [[Bombardier_Dash-8#Series_400|Bombardier Dash 8 Q400]]
| Operator = [[Colgan Air]]
| tail_number = N200WQ
| Passengers = 44
| Crew = 4 + 1 off-duty pilot
| Survivors = 0
| Origin = [[Newark Liberty International Airport]]
| Destination = [[Buffalo Niagara International Airport]]
}}

'''[[Colgan Air]] Flight 3407''', marketed as '''[[Continental Connection]] Flight 3407''', was a [[Continental Airlines]] [[codeshare agreement|code share]] flight operated between [[Newark Liberty International Airport]] (EWR) in [[New Jersey]] and [[Buffalo Niagara International Airport]] (BUF) in [[New York]].

Shortly after its last communication at 10:11 p.m. [[Eastern Time Zone|EST]] on February 12, 2009 (03:11, February 13 [[UTC]]), the plane crashed into a house in the northeast [[Buffalo, New York|Buffalo]] suburb of [[Clarence Center, New York|Clarence Center]], {{convert|6|mi|km}} short of BUF's Runway 23, killing everyone on board. A total of 50 people were killed, including two [[pilot]]s, two [[flight attendant]]s, 44 passengers, one off-duty pilot, and one resident of the house. The crew made no emergency declaration before the crash.<ref>{{Citation
| title = 50 killed as US plane crashes into house
| newspaper = Dawn
| year = 2009
| date = 14-02-2009
| url =http://www.dawn.com/2009/02/14/top10.htm }}</ref> It was the first fatal crash of a commercial airliner in the United States since the crash of [[Comair Flight 191]] in August 2006.

==Flight details==
[[Image:Continental Connection Bombardier Q400.jpg|thumb|left|A Dash 8 Q400 similiar to the aircraft involved.]]
Flight 3407 was a 74-seat [[Bombardier Dash 8|Bombardier Dash 8 Q400]] ([http://www.airliners.net/photo/Continental-Connection-(Colgan/De-Havilland-Canada/1453895/L/&tbl=photo_info&photo_nr=1&sok=keyword_%28%5C%27%2B%5C%22N200WQ%5C%22%5C%27_IN_BOOLEAN_MODE%29%29_&sort=_order_by_photo_id_DESC_&prev_id=&next_id=NEXTID Registration: N200WQ]) twin engine turboprop operated by [[Colgan Air]], equipped with [[deicing boot|deicing boots]]. The Q400 model has been involved in 13 incidents{{clarify}}, but this is the first fatality. This particular plane was put into service in April 2008.<ref name=bloomberg/> It was en route from [[Newark Liberty International Airport]] to [[Buffalo Niagara International Airport]]. The flight was one of seven Continental flights bound for Buffalo Niagara that day, out of a total of 110 incoming and departing flights across all carriers.<ref name=Carey/>

The crew was led by Captain Marvin Renslow, age 47, of [[Lutz, Florida]],<ref>{{cite news|last=Nipps|first=Emily|title=Pilot in Buffalo crash was from Pasco County|work=St. Petersburg Times|date=2009-02-13|url=http://www.tampabay.com/news/publicsafety/accidents/article975671.ece|accessdate=2009-02-14}}</ref> who was hired by Colgan in 2005 and had flown 3,379 hours. First Officer Rebecca Lynne Shaw of [[Maple Valley, Washington]]<ref>[http://www.katu.com/news/local/39566412.html "Co-pilot of crashed plane was from Wash"] (2009-02-13). ''Katu''. Retrieved 2009-02-13.</ref> was hired by Colgan in January 2008, and had flown 2,244 hours. Flight Attendants Matilda Quintero and Donna Prisco both joined Colgan in May 2008. Captain Joseph Zuffoletto, an off-duty crew member aboard flight 3407, was hired by Colgan in September 2005.<ref name=wivb>{{cite web|url=http://www.wivb.com/dpp/news/Flight_3407_crew_members_names_released_090213 |title=Flight 3407 crew members names released |publisher=wivb.com |date=February 13, 2009 |accessdate=February 13, 2009 }}</ref><ref name=cbs2/><br>

==Crash==
[[Image:Dash 8 in planform arp rotated 03.jpg|thumb|right|[[Planform]] view of a Q400 showing the high aspect ratio wings]]
[[File:ILS_RWY_23_KBUF.jpg|thumb|left|FAA ILS/LOC approach plate to Runway 23 at Buffalo Niagara International Airport (KBUF). The flight crashed near the Localizer Outer Marker (LOM) (Identifier: "Klump") about five miles from the threshold of Rwy 23.]]
The aircraft had been cleared for the [[Instrument landing system|ILS]] Runway 23 approach to the nearby [[Buffalo Niagara International Airport]] when it disappeared from [[Radar|radar]]. The last radar position (unofficial) was at 10:11 PM Eastern time. Weather conditions were a [[wintry mix]] in the area, with light snow, fog, and {{convert|17|mph|km/h}} winds. Two other aircraft reported icing conditions around the time of the crash. Last radio contact was made when the plane was 3 miles from a radio beacon, when First Officer Shaw acknowledged a routine instruction to change to tower frequency with the flight's numbers, 3407. After several attempts to hail the crew, controllers requested the assistance of [[Delta Air Lines|Delta]] Flight 1998 and [[US Airways]] Flight 1452, in making visual contact with the missing airplane; the Delta crew responded that they did not see the plane.<ref name=cbs2>[http://www.cbsnews.com/stories/2009/02/13/national/main4799482.shtml All Calm Moments Before Plane Crashes] (2009-02-13). ''CBS News''. Retrieved 2009-02-13.</ref><ref name=buff>{{cite web|url=http://www.buffalonews.com/home/story/577959.html |title=Federal investigators begin searching for the cause of Clarence Center crash |authors=Dale Anderson and Phil Fairbanks |publisher=''[[The Buffalo News]]'' |date=February 12, 2009 |accessdate=February 12, 2009 }}</ref><ref>[http://archive-server.liveatc.net/kbuf/KBUF-Feb-13-2009-0300Z.mp3 Recording of air traffic controller] LiveATC.net Archive for Buffalo, 22:00-22:30 EST</ref><ref name=cbsnews>{{cite web|url=http://www.cbsnews.com/stories/2009/02/13/national/main4798963.shtml |title=Commuter Plane Crashes Into New York Home |publisher=cbsnews.com |date=February 12, 2009 |accessdate=February 12, 2009 }}</ref><ref name=cnn>{{cite web|url=http://www.cnn.com/2009/US/02/13/plane.crash.new.york/index.html |title=Plane with 49 aboard crashes into house in suburban Buffalo |publisher=CNN |date=February 13, 2009 |accessdate=February 13, 2009 }}</ref><ref>[http://archive-server.liveatc.net/kbuf/KBUF-Feb-13-2009-0300Z.mp3 Recording of air traffic controller] LiveATC.net Archive for Buffalo, 22:00-22:30 EST</ref><ref name=fboweb>[http://fboweb.com/track/CJC3407 Track log for Continental Connection flight 3407 (CJC3407) at fboweb.com]</ref><ref name=upi>{{cite web|url=http://www.upi.com/Top_News/2009/02/13/Commuter_plane_crashes_into_house/UPI-22451234502518/ |title=Obama extends sympathies to crash victims|publisher=UPI|date=February 12, 2009 |accessdate=February 12, 2009 }}</ref><ref name=msnbc>{{cite web|url=http://www.msnbc.msn.com/id/29173163/ |title=50 killed as plane slams into home near Buffalo |publisher=[[MSNBC]] |date=February 12, 2009 |accessdate=February 12, 2009 }}</ref>

During the flight, the de-icing system was turned on by the pilots. The flight crew discussed significant ice buildup on the aircraft's wings and windshield shortly before the crash. Following this, the pilots configured the aircraft's flaps and landing gear for landing. Immediately, the plane went through severe pitch and roll oscillations and plunged at a steep angle directly into the private home at 6038 Long Street, Clarence Center, about 5 miles from the end of the runway, and nearly directly under its intended approach path. The lots in the area are only 60 feet wide, but the plane hit the house square on, completely destroying it in the fire but with remarkably little damage to surrounding homes. The house that was hit by the plane was the home of Douglas and Karen Wielinski along with their daughter Jill. Douglas was killed and the other two escaped with minor injuries and were treated at the Millard Fillmore Suburban hospital.<ref name="wben">[http://www.wben.com/WBEN-Exclusive---A-Survivor-Speaks/3848425 Residents Survive After Plane Crashes Through Home]. WBEN 930 Buffalo, NY. 13 February 2009.</ref> The home is around the corner from the Clarence Center Fire Company, so emergency personnel were able to respond quickly. While fighting the blaze, two firefighters were injured. The crash and intense fire caused the evacuation of 12 nearby houses.<ref name=cnn>{{cite web|url=http://www.cnn.com/2009/US/02/13/plane.crash.new.york/index.html |title=Plane with 49 aboard crashes into house in suburban Buffalo |publisher=CNN |date=February 13, 2009 |accessdate=February 13, 2009 }}</ref><ref>[http://www.nydailynews.com/news/2009/02/13/2009-02-13_karen_wielinski_tells_her_story_of_survi.html Karen Wielinski tells her story of survival after Flight 3407 crashed into her home] February 13, 2009</ref><ref>[http://www.cnn.com/2009/US/02/13/plane.crash.escape/ Mom, daughter escape after plane crashes into home] February 13, 2009</ref><ref name=Carey>Carey, Elizabeth (2009-02-13). [http://www.bizjournals.com/albany/stories/2009/02/09/daily46.html Buffalo area plane crash claims 50 lives]. ''The Business Review''. Retrieved 2009-02-13.</ref><ref name=msnbc2>{{cite web|url=http://www.msnbc.msn.com/id/29173163|title=NTSB: Crew reported ice buildup before crash|publisher=[[MSNBC]]|date=February 13, 2009|accessdate=February 13, 2009 }}</ref>

===Fatalities===
[[File:Obama and Beverly Eckert.jpg|thumb|Barack Obama shaking hands with [[Beverly Eckert]] a week before the accident]]
The total number of reported fatalities was 50 (49 on board and one on the ground). There were also four reported injuries on the ground. Among the reported dead were human rights investigator [[Alison Des Forges]], an expert on the [[Rwandan genocide]]; jazz musicians [[Gerry Niewood]] and [[Coleman Mellett]], en route to a concert with [[Chuck Mangione]] and the [[Buffalo Philharmonic Orchestra]]; and [[Beverly Eckert]], who became co-chair of the 9/11 Family Steering Committee and a leader of "Voices of September 11" after her husband Sean Rooney was killed in the [[September 11 attacks]]. Eckert was en route to Buffalo to celebrate her late husband's 58th birthday and to give a scholarship in his memory at [[Canisius High School]].<ref name=tapper/><ref name=bloomberg>Dolmetsch, Chris; Miller, Hugo (2009-02-13). [http://www.bloomberg.com/apps/news?pid=20601087&sid=aJrXDV_00oIk&refer=home Continental Flight Crashes Near Buffalo, Killing 50 (Update3)]. ''Bloomberg.com''. Retrieved 2009-02-13.</ref><ref name=Fox>[http://www.foxnews.com/story/0,2933,492164,00.html Commuter Plane Crashes Into Buffalo-Area Home; 50 Killed]. ''Fox News''. Retrieved 2009-02-13.</ref><ref>[http://www.npr.org/templates/story/story.php?storyId=100676892 Fiery Plane Crash In Upstate N.Y. Kills 50] (2009-02-13). ''NPR''. Retrieved 2009-02-13.</ref><ref name="ocregister">[http://hosted.ap.org/dynamic/stories/P/PLANE_INTO_HOME_MANGIONE?SITE=CAANR&SECTION=HOME&TEMPLATE=DEFAULT Publicist: 2 Mangione musicians die in plane crash]</ref>

==Investigation==
[[Continental Airlines|Continental Airlines Inc.]] said [[Colgan Air|Colgan Air]] was in the process of collecting information.<ref name="Yahoo" /> The [[National Transportation Safety Board]] (NTSB) and [[United States Department of Homeland Security|Department of Homeland Security]] (DHS) announced that they would send a team to the crash site on February 13 to begin the investigation.<ref name=buff/> NTSB spokesman Steve Chealander said that 14 investigators were assigned to the crash of Continental Connection Flight 3407.<ref name="Yahoo">{{cite news|url=http://news.yahoo.com/s/ap/20090213/ap_on_re_us/plane_into_home|title=Fiery plane crash in upstate NY kills 50|last=Wawrow|first=John|date=2009-02-13|publisher=Yahoo!|accessdate=2009-02-13}}</ref> Both the [[Flight Data Recorder]] (FDR) and the [[Cockpit Voice Recorder]] (CVR) have been retrieved and are currently being analyzed in [[Washington, D.C.]]<ref name=msnbc2/><ref name=cbsnewsfdr>{{cite web|url=http://www.cbsnews.com/stories/2009/02/13/national/main4799482.shtml|title=Black Boxes Found From Buffalo Crash |publisher=cbsnews.com |date=February 13, 2009 |accessdate=February 13, 2009 }}</ref>

After initial FDR and CVR analysis, it was determined that the aircraft went through severe pitch and roll oscillations after positioning its flaps and landing gear for landing. Up until this point, the plane had been handling normally. The de-icing system was reported to be turned on.<ref name=msnbc2/><ref name=cbs3>{{cite web|url=http://www.cbsnews.com/stories/2009/02/13/national/main4801448.shtml|title=NTSB: Crew Saw Ice Buildup Before Crash|publisher=cbsnews.com |date=February 13, 2009|accessdate=February 13, 2009 }}</ref>

==Reactions==
[[Colgan Air]] set up a telephone number for families and friends of those affected to call on February 13,<ref name=InsideNova/> and a family assistance center was opened at the Cheektowaga Senior Center in [[Cheektowaga (town), New York|Cheektowaga, New York]].<ref name=Colgan>[http://www.colganair.com/flight3407_press_release.pdf "Colgan Air, Inc. Releases Additional Information Regarding Flight 3407" (PDF)] (2009-02-13). ''Colgan Air''. Retrieved 2009-02-13.</ref> The [[American Red Cross]] also opened reception centers in Buffalo and Newark where family members could receive support from [[mental health]] and spiritual care workers.<ref>[http://www.redcross.org/portal/site/en/menuitem.1a019a978f421296e81ec89e43181aa0/?vgnextoid=f9dc78986407f110VgnVCM10000089f0870aRCRD "Red Cross Provides Comfort and Counseling to Families of Buffalo Plane Crash"]. American Red Cross. Retrieved 2009-02-13.</ref>

U.S. President Barack Obama extended condolences before the 10:30 am Business Council meeting in the [[East Room]] of the [[White House]] on the 13th, thanking the first responders and specifically mentioning Beverly Eckert.<ref name=tapper>Tapper, Jake; Travers, Karen (2009-02-13). [http://blogs.abcnews.com/politicalpunch/2009/02/president-oba-8.html "President Obama Mentions Plane Crash, and Victim Beverly Eckert"]. Retrieved 2009-02-13.</ref> New Jersey [[governor]] [[Jon Corzine]] followed suit, and New York governor [[David Paterson]] plans to visit the site of the crash. Just after 2:30 p.m., the [[U.S. House of Representatives]] held a [[moment of silence]] for the victims and their families.<ref> [http://wcbstv.com/topstories/continental.airlines.crash.2.934547.html "Local Leaders React In Wake Of Flight 3407 Crash"] (2009-02-13). ''WCBSTV''. Retrieved 2009-02-13.</ref>

Philip H. Trenary, President and [[Chief Executive Officer]] of [[Pinnacle Airlines]], Colgan's parent company, also expressed condolences in a [[press release]] on the 13th, and pledged to commit all needed resources necessary to assist in the investigation. The Colgan Air founder and former owner, [[Senate of Virginia|Virginia State Senator]] [[Charles J. Colgan]], made a similar statement.<ref name=InsideNova>Streng, Aileen (2009-02-13). [http://www.insidenova.com/isn/news/local/article/colgan_rushes_to_manassas_after_n.y._plane_crash/29924/ Colgan rushes to Manassas after N.Y. plane crash]. ''InsideNova''.</ref>

==See also==
*[[List of accidents and incidents involving commercial aircraft]]
*[[List of accidents and incidents involving airliners by location]]
*[[US Airways Flight 1549]]
*[[American Eagle Flight 4184]]

==References==
{{reflist|2}}

==External links==
{{Wikinews|Fifty killed in Continental Flight 3407 plane crash in Clarence Center, New York}}
*[http://fboweb.com/pu/info/newss.aspx?ni=320 Flight path for CJC3407 in 3D/Google Earth at fboweb.com]
*[http://fboweb.com/track/CJC3407 Flight track data for Continental Connection flight 3407 at fboweb.com]
*[http://www.continental.com/web/en-US/content/news/flight3407.aspx Information Regarding Flight 3407] - ''[[Continental Airlines]]''
*[http://flightaware.com/live/flight/CJC3407/history/20090213/0031Z/KEWR/KBUF Flight tracker] and [http://flightaware.com/live/flight/CJC3407/history/20090213/0220Z/KEWR/KBUF/tracklog Track log]
* [http://www.youtube.com/watch?v=HvbauxB7n18 CNN Fireman Interview]
* [http://flickr.com/photos/wnymedia/sets/72157613715506345/ Flickr photo set of the crash]
* [http://www.supload.com/listen?s=8QeAxT / ATC Recording of flight 3407]
* [http://www.airliners.net/photo/Continental-Connection-(Colgan/De-Havilland-Canada/1453895 A picture of the aircraft taken in late 2008.]

{{coord|43.011602|-78.63904|type:landmark_region:USNY|display=title}}

[[Category:2009 in the United States]]
[[Category:Accidents and incidents on commercial airliners in the United States]]
[[Category:Airliner accidents and incidents with an unknown cause]]
[[Category:Aviation accidents and incidents in 2009]]
[[Category:Continental Airlines]]
[[Category:Erie County, New York]]

[[es:Vuelo 3407 de Continental Airlines]]
[[fr:Vol 3407 Continental Airlines]]
[[nl:Continental Airlines vlucht 3407]]
[[ja:コンチネンタル航空3407便]]
[[no:Continental Airlines Flight 3407]]
[[pl:Katastrofa lotu Continental Express 3407]]
[[pt:Voo Continental Airlines 3407]]
[[ro:Zborul 3407 al Continental Airlines]]
[[ru:Рейс 3407 авиакомпании Continental Airlines]]
[[vi:Chuyến bay 3407 của Continental Airlines]]
[[wuu:美国大陆航空公司3407号航班]]
[[zh:美国大陆航空3407号班机空难]]

United-Airlines-Flug 173

2007-12-14T17:33:57Z

EditorASC: /* Aftermath */ Add SAS flight 993, to the list of similar accidents

{{Crash infobox|name=United Airlines Flight 173|
Date=[[December 28]], [[1978]] |
Type=Pilot Error |
Site=[[Portland, Oregon]]|
Fatalities=10|
Injuries=24 |
Aircraft Type=[[Douglas DC-8|McDonnell-Douglas DC-8-61]]|
Operator=United Airlines|
Tail Number=N8082U |
Passengers=181|
Crew=8 |
Survivors = 179|
}}

'''United Airlines Flight 173''', registration N8082U<ref>{{cite web |url=http://aviation-safety.net/database/record.php?id=19781228-1&lang=en |title=Accident description |publisher=Aviation Safety Network |accessdate=2006-08-16}}</ref>, was a [[Douglas DC-8|Douglas DC-8-61]] en route from [[Denver]] to [[Portland, Oregon]], on [[December 28]], [[1978]]. When the landing gear was lowered, only two of the green landing gear indicator lights came on. The plane circled in the vicinity of Portland while the crew investigated the problem. The plane eventually ran out of fuel and crashed in a sparsely populated area near 158th and East Burnside Ave, killing 10 and seriously injuring 24 of the 181 on board.

==Crash investigation and report==

The NTSB investigation revealed that when the landing gear was lowered, a loud thump was heard. That unusual sound was accompanied by abnormal vibration and an abnormal yaw of the aircraft. The right main landing gear retract cylinder assembly had failed, due to corrosion, and that allowed the right gear to free fall. Although the RMG was down and locked, the rapid and abnormal free fall damaged the mircroswitch, which completed the circuit to the cockpit green light, which tells the pilots that gear is down and locked. It was those unusual indicators (loud noise, vibration, yaw and no green light) which led the captain to abort the landing, so that they would have time to diagnose the problem and prepare the passengers for an emergency landing. While the decision to abort the landing was correct, the accident occurred because the flight crew became so absorbed with diagnosing the problem that they failed to calculate a time when they must be landing, to avoid fuel starvation.

"The Safety Board believes that this accident exemplifies a recurring problem --a breakdown in cockpit management and teamwork during a situation involving malfunctions of aircraft systems in flight....Therefore, the Safety Board can only conclude that the flightcrew failed to relate the fuel remaining and the rate of fuel flow to the time and distance from the airport, because their attention was directed almost entirely toward diagnosing the landing gear problem." <ref name=ntsb>[http://amelia.db.erau.edu/reports/ntsb/aar/AAR79-07.pdf NTSB Report (PDF)]</ref>

The NTSB determined the following [[probable cause]]:<ref name=ntsb/><blockquote>"The failure of the captain to monitor properly the aircraft's fuel state and to properly respond to the low fuel state and the crewmember's advisories regarding fuel state. This resulted in [[fuel starvation|fuel exhaustion]] to all engines. His inattention resulted from preoccupation with a landing gear malfunction and preparations for a possible landing emergency."</blockquote>

The NTSB also determined the following contributing factor:<blockquote>"The failure of the other two flight crewmembers either to fully comprehend the criticality of the fuel state or to successfully communicate their concern to the captain."</blockquote>

==Aftermath==
As a result of this accident United Airlines instituted the industry's first [[Crew Resource Management|Crew Resource Management/Cockpit Resource Management]] for pilots, in 1980. (CRM) program, which proved to be so successful that it is now used throughout the world.

Other aircraft accidents involving faulty landing gear indicator lights were [[Eastern Air Lines Flight 401]], which crashed while circling around the airport at Miami, on December 29, 1972, and SAS Flight 993, on January 13, 1969, which crashed into the ocean during an approach to LAX.

The Eastern crew became pre-occupied with the nose gear indicator light problem and accidentally disconnected the autopilot, causing the aircraft to make a slow descent and crash into the Everglades. Further investigation revealed that the nose gear was down and locked. It was the same for the SAS flight, as the green light for the nose gear failed to illuminate, after the landing gear was lowered. The SAS cockpit crew became so occupied with attempting to diagnose the lack of a nose gear green light, that they allowed their rate of descent to increase, until that DC-8-62 crashed into the ocean, well short of the runway.

FAA registration N8082U was set to suffer another tragic fate on [[July 27]], [[2007]], in [[Oshkosh, Wisconsin|Oshkosh]], [[Wisconsin]]. A homebuilt [[North American P-51|P-51A]] with the identical registration suffered a fatal accident while landing at the [[Experimental Aircraft Association| EAA]] [[EAA AirVenture Oshkosh| AirVenture]] following a flight demonstration. <ref>http://www.ntsb.gov/ntsb/brief.asp?ev_id=20070801X01080&key=1</ref>

==See also==
* [[Lists of accidents and incidents on commercial airliners]]
* [[Air safety]]

==References==
<references/>

==External links==
* [http://aviation-safety.net/database/record.php?id=19781228-1 Aviation Safety Network for United 173]
*[http://www.planecrashinfo.com/1978/1978-76.htm Accident details] at [http://www.planecrashinfo.com/ planecrashinfo.com]
*[http://www.airliners.net/search/photo.search?regsearch=N8082U Photos of N8082U] at [http://www.airliners.net Airliners.net]
*[http://www.airdisaster.com/photos/ua173/photo.shtml Photos of Accident site] at [http://www.airdisaster.com AirDisaster.com]
{{Geolinks-US-buildingscale|45.5225|-122.499722}}

[[Category:Accidents and incidents on commercial airliners in the United States]]
[[Category:Airliner crashes caused by pilot error]]
[[Category:Fuel exhaustion on commercial airliners]]
[[Category:Aviation accidents and incidents in 1978]]
[[Category:1978 in the United States]]
[[Category:United Airlines flights]]
[[Category:Disasters in Oregon]]

United-Airlines-Flug 173

2007-12-14T16:43:25Z

EditorASC: Expanded the details of why this crash occurred, and noted that a mechanical failure of part of the right main gear, precipited the events that eventually led to the crash.

{{Crash infobox|name=United Airlines Flight 173|
Date=[[December 28]], [[1978]] |
Type=Pilot Error |
Site=[[Portland, Oregon]]|
Fatalities=10|
Injuries=24 |
Aircraft Type=[[Douglas DC-8|McDonnell-Douglas DC-8-61]]|
Operator=United Airlines|
Tail Number=N8082U |
Passengers=181|
Crew=8 |
Survivors = 179|
}}

'''United Airlines Flight 173''', registration N8082U<ref>{{cite web |url=http://aviation-safety.net/database/record.php?id=19781228-1&lang=en |title=Accident description |publisher=Aviation Safety Network |accessdate=2006-08-16}}</ref>, was a [[Douglas DC-8|Douglas DC-8-61]] en route from [[Denver]] to [[Portland, Oregon]], on [[December 28]], [[1978]]. When the landing gear was lowered, only two of the green landing gear indicator lights came on. The plane circled in the vicinity of Portland while the crew investigated the problem. The plane eventually ran out of fuel and crashed in a sparsely populated area near 158th and East Burnside Ave, killing 10 and seriously injuring 24 of the 181 on board.

==Crash investigation and report==

The NTSB investigation revealed that when the landing gear was lowered, a loud thump was heard. That unusual sound was accompanied by abnormal vibration and an abnormal yaw of the aircraft. The right main landing gear retract cylinder assembly had failed, due to corrosion, and that allowed the right gear to free fall. Although the RMG was down and locked, the rapid and abnormal free fall damaged the mircroswitch, which completed the circuit to the cockpit green light, which tells the pilots that gear is down and locked. It was those unusual indicators (loud noise, vibration, yaw and no green light) which led the captain to abort the landing, so that they would have time to diagnose the problem and prepare the passengers for an emergency landing. While the decision to abort the landing was correct, the accident occurred because the flight crew became so absorbed with diagnosing the problem that they failed to calculate a time when they must be landing, to avoid fuel starvation.

"The Safety Board believes that this accident exemplifies a recurring problem --a breakdown in cockpit management and teamwork during a situation involving malfunctions of aircraft systems in flight....Therefore, the Safety Board can only conclude that the flightcrew failed to relate the fuel remaining and the rate of fuel flow to the time and distance from the airport, because their attention was directed almost entirely toward diagnosing the landing gear problem." <ref name=ntsb>[http://amelia.db.erau.edu/reports/ntsb/aar/AAR79-07.pdf NTSB Report (PDF)]</ref>

The NTSB determined the following [[probable cause]]:<ref name=ntsb/><blockquote>"The failure of the captain to monitor properly the aircraft's fuel state and to properly respond to the low fuel state and the crewmember's advisories regarding fuel state. This resulted in [[fuel starvation|fuel exhaustion]] to all engines. His inattention resulted from preoccupation with a landing gear malfunction and preparations for a possible landing emergency."</blockquote>

The NTSB also determined the following contributing factor:<blockquote>"The failure of the other two flight crewmembers either to fully comprehend the criticality of the fuel state or to successfully communicate their concern to the captain."</blockquote>

==Aftermath==
As a result of this accident United Airlines instituted the industry's first [[Crew Resource Management|Crew Resource Management/Cockpit Resource Management]] for pilots, in 1980. (CRM) program, which proved to be so successful that it is now used throughout the world.

Another aircraft accident involving a faulty landing gear indicator was [[Eastern Air Lines Flight 401]], which crashed while circling around the airport. The crew was pre-occupied with the nose gear problem and accidentally disabled the autopilot causing the aircraft to make a slow descent and crash into the Everglades. Further investigation revealed that the nose gear had, in fact, been lowered.

FAA registration N8082U was set to suffer another tragic fate on [[July 27]], [[2007]], in [[Oshkosh, Wisconsin|Oshkosh]], [[Wisconsin]]. A homebuilt [[North American P-51|P-51A]] with the identical registration suffered a fatal accident while landing at the [[Experimental Aircraft Association| EAA]] [[EAA AirVenture Oshkosh| AirVenture]] following a flight demonstration. <ref>http://www.ntsb.gov/ntsb/brief.asp?ev_id=20070801X01080&key=1</ref>

==See also==
* [[Lists of accidents and incidents on commercial airliners]]
* [[Air safety]]

==References==
<references/>

==External links==
* [http://aviation-safety.net/database/record.php?id=19781228-1 Aviation Safety Network for United 173]
*[http://www.planecrashinfo.com/1978/1978-76.htm Accident details] at [http://www.planecrashinfo.com/ planecrashinfo.com]
*[http://www.airliners.net/search/photo.search?regsearch=N8082U Photos of N8082U] at [http://www.airliners.net Airliners.net]
*[http://www.airdisaster.com/photos/ua173/photo.shtml Photos of Accident site] at [http://www.airdisaster.com AirDisaster.com]
{{Geolinks-US-buildingscale|45.5225|-122.499722}}

[[Category:Accidents and incidents on commercial airliners in the United States]]
[[Category:Airliner crashes caused by pilot error]]
[[Category:Fuel exhaustion on commercial airliners]]
[[Category:Aviation accidents and incidents in 1978]]
[[Category:1978 in the United States]]
[[Category:United Airlines flights]]
[[Category:Disasters in Oregon]]