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Main article: General Dynamics/Grumman F-111B
F-111B
An F-111B approaching the USS Coral Sea (CV-43) in July 1968
Role Fighter interceptor
National origin United States
Manufacturer General Dynamics/Grumman]]
First flight 21 December 1964
Primary user United States Navy
Number built 5?
Developed from General Dynamics F-111

The General Dynamics F-111 is a medium-range interdictor and tactical strike aircraft that also fills the roles of strategic bomber, reconnaissance and electronic warfare in its various versions. Developed in the 1960s and first entering service in 1967, the United States Air Force (USAF) variants were officially retired by 1998. The Royal Australian Air Force (RAAF) is the remaining operator of the F-111.

The F-111 pioneered several technologies for production military aircraft, including variable-sweep wings, afterburning turbofan engines, and automated terrain following radar for low-level, high-speed flight. Its design was highly influential, particularly for Soviet engineers, and some of its advanced features have since become commonplace. During its inception, however, the F-111 suffered a variety of development problems, and several of its intended roles, such as naval interception, failed to materialize.

In USAF service the F-111 has been effectively replaced by the F-15E Strike Eagle for medium-range precision strike missions, while the supersonic bomber role has been assumed by the B-1B Lancer. In 2007, the RAAF decided to replace its 21 F-111s in 2010 with 24 F/A-18F Super Hornets.[1][2]

Development

The beginnings of the F-111 were in the TFX program, an ambitious early 1960s project to combine the United States Air Force requirement for a fighter-bomber to replace the F-105 Thunderchief with the United States Navy's need for a long-range carrier-based Fleet Air Defense fighter to replace the F-4 Phantom II. The fighter design philosophy of the day concentrated on very high speed, raw power, and air-to-air missiles.

Early requirements

The U.S. Air Force's Tactical Air Command (TAC) was largely concerned with the fighter-bomber and deep strike/interdiction roles, which in the early 1960s still focused on the use of tactical nuclear weapons. The aircraft would be a follow-on to the F-105 Thunderchief, which was designed to deliver nuclear weapons low, fast and far. Air combat would be an afterthought until encountering MiGs over Vietnam in the mid-1960s. In June 1960 the USAF issued a specification for a long-range interdiction/strike aircraft able to penetrate Soviet air defenses at very low altitudes and very high speeds to deliver tactical nuclear weapons against crucial targets.[3]

Meanwhile the U.S. Navy sought a long-range, high-endurance interceptor to defend its carrier battle groups against the new generation of Soviet jet bombers, which by then were being armed with large, long range anti-ship missiles. The Navy needed a Fleet Air Defense (FAD) aircraft with range and load-carrying ability than the F-4 Phantom II, and one equipped with a powerful radar and a battery of long-range missiles to intercept both enemy bombers and their missiles. The Navy had studied, but rejected, a subsonic, straight-winged missile carrier, the F6D Missileer. The Navy had tried variable geometry with the XF10F Jaguar but abandoned that in 1953. By late 1960, the Navy had been reconsidering variable geometry for the FAD requirement. Variable geometry offered a compromise between swept wing for high speeds and a modestly swept wing with better payload, range and landing characteristics. This would allow larger and faster aircraft to land on an aircraft carrier.

Tactical Fighter Experimental (TFX)

The Air Force and Navy requirements appeared to be different. However, on 14 February 1961 the new U.S. Secretary of Defense, Robert McNamara, formally directed that the services study the development of a single aircraft that would satisfy both requirements. Early studies indicated the best option was to base the Tactical Fighter Experimental (TFX) on the Air Force requirement and a modified version for the Navy.[4] In June 1961, Secretary McNamara ordered the go ahead on TFX despite Air Force and the Navy efforts to keep their programs separate.[5] The USAF and the Navy could only agree on swing-wing, two seat, twin engine design features. The USAF wanted a tandem seat aircraft for low level penetration, while the Navy wanted a shorter, high altitude interceptor with side by side seating.[4] Also, the USAF wanted the aircraft designed for 7.33 g with Mach 2.5 speed at altitude and Mach 1.2 speed at low level with a length of 66-72 ft (20.1-21.9 m). The Navy had less strenuous requirements of 6 g with Mach 2 speed at altitude and high subsonic speed (approx. Mach 0.9) at low level with a length of 56 ft (17.1 m).[4][6] So McNamara developed a basic set of requirements for TFX based largely on the Air Force's requirements. Then on 1 September 1961 he ordered the USAF to develop it.[4][6]

A request for proposals (RFP) for the TFX was provided to industry in October 1961. In December of that year proposals were received from Boeing, General Dynamics, Lockheed, McDonnell, North American and Republic. The proposal evaluation group found all the proposals lacking but the best should be improved under study contracts. Boeing and General Dynamics were selected to enhance their designs. Boeing's proposal was recommended by the selection board in January 1962. However, the Boeing's engine was not considered acceptable. Switching to a crew capsule and alterations to radar and missile storage were also needed. The companies provided updated proposals in April 1962. Air Force reviewers favored Boeing's offering, but the Navy found both submissions unacceptable for its operations. Two more rounds of updates to the proposals were conducted with Boeing being picked by the selection board. Instead Secretary McNamara selected General Dynamics' proposal in November 1962 due to its greater commonality between Air Force and Navy TFX versions. The Boeing aircraft versions shared less than half of the major structural components. General Dynamics signed the TFX contract in December 1962. A Congressional investigation followed, but could not change the selection.[7]

The F-111A and B variants used the same airframe structural components and TF30-P-1 turbofan engines. They featured side by side crew seating in escape capsule as required by the Navy. The F-111B's nose was 8.5 feet (2.59 meters) shorter due to its need to fit on existing carrier elevator decks, and had 3.5 feet (1.07 meters) longer wingtips to to improve on-station endurance time. The Navy version would carry a AN/AWG-9 Pulse-Doppler radar and six AIM-54 Phoenix missiles. The Air Force version would carry the AN/APQ-113 attack radar and the AN/APQ-110 terrain-following radar and air-to-ground armament. Titanium was planned for most of the airframe. However, this proved to be too expensive and more conventional metals were used instead.[8]

With General Dynamics lacking experience with carrier-based fighters, it teamed with Grumman for the assembly and test the F-111B aircraft. In addition, Grumman would also build the F-111A's aft fuselage and the landing gear. The F-111A mock-up was inspected in September 1963. The first test F-111A was rolled out of the General Dynamics' Fort Worth, Texas plant on 15 October 1964. It was powered by YTF30-P-1 turbofans and used a set of ejector seats as the escape capsule was not yet available.[8] The F-111A first flew on 21 December 1964 from Carswell AFB, Texas.[9] During early flight testing, the F-111A achieved a speed of Mach 1.3. The second F-111A flew for the first time on 25 February 1965.[8] The first F-111B was also equipped with ejector seats and first flew on 18 May 1965.[10]

F-111 development continued. Flight testing of the F-111A ran through 1973.[11] The F-111B was canceled by the Navy in 1968 due to weight and performance issues.[12] The F-111C model was developed for Australia. Subsequently, the improved F-111E, F-111D, F-111F models were developed for the US Air Force. The strategic bomber FB-111A and the EF-111 electronic warfare versions were later developed for the USAF.[13] Production ended in 1976[14] with a total of 563 F-111 variants built.[15]

Design

F-111 cockpit prior to a night flight.

The F-111 is an all-weather attack aircraft capable of low-level penetration of enemy defenses to deliver ordnance on the target.[16] The F-111 features variable geometry wings, an internal weapons bay and a cockpit with side by side seating. The cockpit is part of an escape crew capsule.[17] The wing sweep varies between 16 degrees and 72.5 degrees (full forward to full sweep).[18]

Armament

Although conceived as a multi-role fighter, the F-111 became a long-range attack aircraft primarily armed with air-to-surface ordnance.

Weapons bay

The F-111 has an internal weapons bay under the fuselage for various weapons.

  • Cannon: All tactical combat versions (that is, not the EF-111A or FB-111A/F-111G) could carry a single M61 Vulcan 20 mm cannon with a very large (2,084 round) ammunition tank, covered by an eyelid shutter when not in use. Although carried by some USAF aircraft, the cannon was never actually used in combat, and was removed by the early 1980s; provision for the cannon has also been deleted from Australian F-111Cs.
  • Bombs: The bay can alternately hold two conventional bombs, usually the Mk 117 type of nominal 750 lb/340 kg weight, although weapons up to the Mk 118 (3,000 lb/1,400 kg) were cleared.
  • Nuclear weapons: All F-111 models except the EF-111A and the Australian F-111C were equipped to carry various free-fall nuclear weapons: tactical models generally carried the B43, B57, or B61. The FB-111A was a dedicated nuclear bomber for most of its life, and carried all of those weapons just mentioned, as well as the B83 and the AGM-69 Short Range Attack Missile. The FB-111A could carry one or two AGM-69 SRAM nuclear missiles in its weapons bay and up to four SRAMs on external wing pylons.
  • Sensor pod: The F-111C and F-111F were equipped to carry the AN/AVQ-26 Pave Tack targeting system on a rotating carriage that kept the pod protected within the weapons bay when not in use. Pave Tack is a FLIR and laser rangefinder/designator that allows the F-111 to designate and drop laser-guided bombs.
  • Reconnaissance pallet: Australian RF-111Cs carry a package of reconnaissance sensors and cameras for tactical recce missions. It contains two video cameras, a Honeywell AN/AAD-5 infrared linescan (recorded on video or film), a Fairchild KA-56E low-altitude and KA-93A4 high-altitude panoramic cameras, and a pair of CAI KS-87C split vertical cameras. It can also record photographs of the attack radar's display.
  • Missiles: The F-111B was intended to be capable of carrying two AIM-54 Phoenix air-to-air missiles in the bay. General Dynamics proposed an arrangement that would allow two AIM-9 Sidewinders to be carried on a trapeze mounting in the bay (at the expense of the M61 cannon), along with a single (usually nuclear) bomb. This was not adopted, with the USAF and RAAF opting for the cannon instead. The AIM-7 Sparrow or AIM-4 Falcon, standard on the F-4 Phantom II, was never fitted, though later F-111 models had radars equipped to guide the Sparrow.[citation needed]
  • Other equipment: Auxiliary fuel tanks and baggage pods were sometimes carried.
F-111F aircraft releasing its load of Mark 82 high-drag bombs over the Bardenas Reales range.
External ordnance

The design of the F-111's fuselage prevents the carriage of external weapons under the fuselage (although there are two small stations, one on the weapon bay, the other on the rear fuselage between the engines, for ECM pods and/or datalink pods for guided weapons). All aircraft, except the FB-111A have provision for eight underwing pylons, four under each wing, with a capacity of 6,000 lb (2,700 kg) each. The inner pylons (3, 4, 5 and 6) pivot with the wing, but only one on each side can be loaded at maximum sweep. The outer pylons (1, 2, 7 and 8) are fixed, and can be loaded only if the wings are spread at less than 26°, causing drag at takeoff angle. The outermost pylons (1 and 8) have never been used operationally, and the second pair of fixed pylons (2 and 7) are fitted only rarely, for the carriage of fuel tanks. FB-111/F-111G models have provision to jettison their empty pylons in flight, reducing drag.

The limited number of fully swiveling pylons restricts the F-111's maximum practical weapons load, since the aircraft cannot use all pylons with the wings fully swept. By contrast, aircraft such as the F-14 and Tornado can carry their maximum bomb loads with fully swept wings.

An F-111 carrying BLU-107 Durandals.

The primary external armament of USAF tactical F-111s included:

Although all F-111s can carry laser-guided munitions, only those with Pave Tack (i.e., F-111F and Australian F-111C) are capable of self-designation. Others can drop laser-guided weapons only with the aid of another ground or air designator.

From the early 1980s onward, tactical F-111s were fitted with shoulder rails on the sides of the outboard swiveling pylon (designated stations 3A and 6A) for two AIM-9 Sidewinder air-to-air missiles for self-defense. The standard Sidewinder fit was the AIM-9P, rather than the more modern AIM-9L or AIM-9M, whose larger fins were not compatible with the shoulder rail. The RAAF has considered replacing the Sidewinder with ASRAAM.

FB-111As could carry the same conventional ordnance as their tactical brothers, but their wing pylons were more commonly used for either fuel tanks or strategic nuclear gravity bombs. Until the weapon was withdrawn in 1990, they could carry up to four AGM-69 SRAM nuclear missiles on the wing pylons, although two was the more normal fit.

Australian F-111Cs have been equipped to launch the AGM-84 Harpoon anti-ship missile, AGM-88 HARM anti-radiation missile, and the AGM-142 Popeye stand-off missile.


Operational history

United States

Combat Lancer F-111As over South-East Asia in 1968

The first production F-111s were delivered on 18 July 1967 to the 428th, 429th and 430th Tactical Fighter Squadrons of the 474th Tactical Fighter Wing based at first out of Cannon AFB, New Mexico, which relocated in 1968 to Nellis AFB.

After early testing a detachment of six aircraft were sent in March 1968 to Southeast Asia for Combat Lancer testing in real combat conditions in Vietnam. In little over a month, three aircraft were lost and the combat tests were halted. It turned out that all three had been lost through malfunction (primarily with the terrain-following radar), not by enemy action. This caused a storm of political recrimination, with U.S. senators denouncing Secretary of Defense McNamara's judgment in procuring the aircraft. It was not until July 1971 that the 474 TFW was fully operational.

September 1972 saw the F-111 back in Southeast Asia, participating in the final month of Operation Linebacker and later the Operation Linebacker II aerial offensive against the North. F-111 missions did not require tankers or ECM support, and they could operate in weather that grounded most other aircraft. One F-111 could carry the bomb load of four F-4 Phantom IIs. The worth of the new aircraft was beginning to show, and over 4,000 combat F-111A missions were flown over Vietnam with only six combat losses.

In 1977, under Operation Creek Swing/Ready Switch the remaining F-111As were transferred from Nellis AFB, Nevada to the 366 TFW based at Mountain Home AFB, equipping the 389th, 390th, and 391st TFS. As the Ready Switch component of that operation, F-111Fs and their crews flew their aircraft to RAF Lakenheath, England to replace the F-4s and their crews of the 492nd, 493rd, and 494th Tactical Fighter Squadrons. As part of that operation, the F-4s from Lakenheath may have moved to Nellis AFB, Nevada.

On 14 April 1986, 18 F-111s and approximately 25 Navy aircraft executed Operation El Dorado Canyon by conducting air strikes against Libya. The 18 F-111s belonging to the 48th Tactical Fighter Wing flew what turned out to be the longest fighter combat mission in history.[19] The round-trip flight between RAF Lakenheath, United Kingdom and Libya of 6,400 miles (10,300 km) spanned 13 hours. One F-111 was shot down over Libya.[19]

In Desert Storm, F-111Fs completed 3.2 successful strike missions for every unsuccessful one, making it 47% more capable than the next leading strike aircraft.[20] The small 66-plane F-111F force was credited with 1,500 kills of Iraqi tanks and other mechanized vehicles. The F-111F was the only Desert Storm aircraft to deliver the GBU-15 and the 5,000-pound laser-guided, penetrating GBU-28.

The F-111 was in service with the USAF from 1967 through 1998. The Strategic Air Command had FB-111s in service from 1969 through 1990. At a ceremony marking the F-111's USAF retirement, on 27 July 1996, it was officially named Aardvark, its long-standing unofficial nickname. Aardvark literally means "earth pig" in Dutch/Afrikaans, consequently, in Australia, the F-111 is often known by the affectionate nickname "Pig". The USAF retired the EF-111 variant in 1998.

F-111B

The F-111B was to be a fleet air defense (FAD) fighter for the U.S. Navy, fulfilling a long-standing naval requirement for a fighter capable of carrying heavy, long-range missiles to defend carriers and their battle groups from Soviet bombers and fighter-bombers equipped with anti-ship missiles. The Navy had just cancelled the F6D Missileer, a concept for a slow, straight-winged jet with the advanced Hughes AN/AWG-9 pulse-Doppler radar, which could detect low flying targets among ground clutter, and lift eight new AIM-54 Phoenix long range, air-to-air missiles, which could attack multiple aircraft simultaneously at ranges out to 100 miles (160 km). The concept was soon cancelled, but the F-111 offered a platform with the range, payload, and Mach 2 performance of a fighter to intercept targets quickly, but with swing wings and turbofan engines, it could also loiter on station for long periods. The F-111B would carry six Phoenix missiles, but have no gun or other short range armament. General Dynamics, having no experience with carrier-based aviation, partnered with Grumman for this version.

The F-111B was a compromise that attempted to reconcile the Navy's very different needs with an aircraft whose basic configuration was largely set by the USAF need for a supersonic strike aircraft. These compromises would harm both USAF and USN versions. The side-by-side seating was preferred by the Navy from the Missileer. The F-111B was shorter than the F-111A, in order to enable it to fit on aircraft carrier deck edge elevators between the flight deck and the hangar deck. The F-111B also had a longer wingspan than its USAF counterpart (70 ft/21.3 m compared to 63 ft/19.2 m) for increased range and cruising endurance. Although the Navy had wanted a 48-inch (122 cm) radar dish for long range, they were forced to accept a 36-inch (91.4 cm) dish for compatibility. The Navy had requested a maximum takeoff weight of 50,000 lb (22,686 kg), but then-Secretary of Defense Robert S. McNamara forced the Navy to compromise at 55,000 lb (24,955 kg). This weight goal proved to be overly optimistic.

Catapult launch of F-111B BuNo 151974 from the USS Coral Sea

Excessive weight plagued the F-111B throughout its development. The prototypes were far over the 55,000 lb (24,955 kg) limit. Design efforts reduced airframe weight but were offset by the addition of the escape capsule. The excessive weight made the aircraft seriously underpowered. In landing configuration at carrier weights, the F-111B could not maintain level flight on one engine, which would be a major problem once committed to the approach.[citation needed] Worse, its visibility for carrier approach and landing were abysmal.

Requirements for the F-111B had been formulated before air combat over Vietnam in 1965 showed the Navy still had a need for an aircraft which could engage MiG fighters at close range. The Navy desired a fighter with more performance than the F-4 Phantom II, yet in trials, the maneuverability and performance of the F-111B, especially in the crucial medium-altitude regimen, was decidedly inferior to the Phantom. During the congressional hearings for the aircraft, Vice Admiral Thomas F. Connolly, then Deputy Chief of Naval Operations for Air Warfare, famously responded to a question from Senator John C. Stennis as to whether a more powerful engine would cure the aircraft's woes with "There isn't enough power in all Christendom to make that airplane what we want!"[21]

By October 1967, the Navy was finally convinced that the F-111B program was a lost cause and recommended its cancellation, which occurred in 1968 after seven had been delivered,[22] two of which had crashed. The swing-wing configuration, TF-30 engines, Phoenix missiles and radar developed for this aircraft (and the earlier, canceled F6D Missileer) were used on its replacement, the F-14 Tomcat, also designed by Grumman. The Tomcat would be large enough to carry the AWG-9 and Phoenix weapons system while exceeding the agility and speed of the F-4 Phantom.

Aircraft on display

F-111B
  • 151972 - Naval Air Weapons Station China Lake, CA (possibly scrapped)
  • 152715 - Naval Air Weapons Station China Lake, CA (last complete F-111B)

Specifications (F-111F)

An orthographically projected diagram of the F-111.
An orthographically projected diagram of the F-111.

Data from Miller,[23] Quest for Performance[24]

General characteristics

Performance

Armament

  • Guns: 1× M61 Vulcan 20 mm (0.787 in) gatling cannon (seldom fitted)
  • Hardpoints: external hardpoints have a capability of 31,500 lb (14,300 kg) of ordnance

See also

Related development

Aircraft of comparable role, configuration, and era

Related lists

References

Notes
  1. ^ Cite error: The named reference SH_buy was invoked but never defined (see the help page).
  2. ^ Cite error: The named reference SH_confirm was invoked but never defined (see the help page).
  3. ^ Gunston 1978, pp. 12–13.
  4. ^ a b c d Gunston 1978, pp. 8–17.
  5. ^ Eden 2004, pp. 196-197.
  6. ^ a b Miller 1982, pp. 11–15.
  7. ^ Gunston 1978, pp. 18–20.
  8. ^ a b c "General Dynamics F-111A", Joe Baugher's site, December 23, 1999.
  9. ^ Eden 2004, p. 197.
  10. ^ "General Dynamics/Grumman F-111B", Joe Baugher's site, 7 November 2004.
  11. ^ Logan 1998, p. 32.
  12. ^ Donald, David ed. "General Dyanic F-111". The Complete Encyclopedia of World Aircraft. Barnes & Nobel Books, 1997. ISBN 0-7607-0592-5.
  13. ^ Frawley, Gerald. "General Dynamics F-111 Aardvark". The International Directory of Military Aircraft, 2002/2003. Aerospace Publications, 2002. ISBN 1-875671-55-2.
  14. ^ Miller 1982, p. 65.
  15. ^ Logan 1998, p. 9.
  16. ^ General Dynamics F-111D to F Aardvark, US Air Force National Museum.
  17. ^ Eden 2004, pp. 196–201.
  18. ^ F-111 design, globalsecurity.org
  19. ^ a b Boyne, Walter J. "El Dorado Canyon", Air Force Magazine, March 1999.
  20. ^ Archive
  21. ^ "Tests & Testimony", Time magazine, 22 March 1968.
  22. ^ General Dynamics/Grumman F-111B, J Baugher, November 7, 2004.
  23. ^ Miller 1982, pp. 32–38, 66.
  24. ^ Loftin, LK, Jr. Quest for performance: The evolution of modern aircraft. NASA SP-468, NASA, 6 August 2004. Retrieved: 22 April 2006.
Bibliography
  • Eden, Paul, ed. "General Dynamics F-111 Aardvark/EF-111 Raven". Encyclopedia of Modern Military Aircraft. London: Amber Books, 2004. ISBN 1-90468-784-9.
  • Gunston, Bill. F-111. New York: Charles Scribner's Sons, 1978. ISBN 0-684-15753-5.
  • Logan, Don. General Dynamics F-111 Aardvark. Atglen, PA: Schiffer Military History, 1998. ISBN 0-7643-0587-5.
  • Miller, Jay. General Dynamics F-111 "Arardvark". Fallbrook, California: Aero Publishers, 1982. ISBN 0-8168-0606-3.
  • Neubeck, Ken. F-111 Aardvark Walk Around. Carrollton, Texas: Squadron/Signal Publications, 2009. ISBN 978-0-89747-581-5
  • Thornborough, Anthony M. F-111 Aardvark. London: Arms and Armour, 1989. ISBN 0-85368-935-0.
  • Winchester, Jim, ed. "General Dynamics FB-111A". "Grumman/General Dynamics EF-111A Raven". Military Aircraft of the Cold War (The Aviation Factfile). London: Grange Books plc, 2006. ISBN 1-84013-929-3.
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