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ITS-8

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Role Motor-glider
National origin Poland
Manufacturer Institute of gliding techniques (I.T.S.), University of Lwów
Designer Wieslaw Stępniewski
First flight late August 1936
Number built 2

The ITS-8 was a twin-boom motor glider

Design and development

In the mid-1930s there was growing Polish interest in low cost powered gliders and and other small, low powered, structurally simple aircraft. The Lwów University's Institute of Gliding Techniques studies of motor gliders was guided by FAI specifications for the new International Powered Glider Class and received funding from LOPP. the ITS-8 was designed to have a gliding performance competitive with contemporary intermediate and high performance unpowered machines. These specifications suggested a conventional glider nose and forward fuselage was required, hence a pusher engine and, to avoid a pylon engine mounting, a twin-boom layout.[1]

The wooden ITS-8 had a high wing which was built around single box spar and a plywood-covered leading edge forming a torsion box. An auxiliary spar carried differential ailerons. In plan the outer wings had a swept leading edges and unswept trailing edges. The rectangular centre section, which was braced on each side with a pair of steel tube struts from the lower fuselage, was ply-covered overall but the outer wing was fabric covered behind the main spar. Two versions of the aircraft had been planned from the start: the low-powered ITS-8, with a 13.6 m (44 ft 7 in)} span and an aspect ratio of 10.1 and the higher-powered ITS-8W with a greater 14.2 m (46 ft 7 in) span and an aspect ratio of 12.5. The ITS-8W also had a higher speed airfoil section centre section, though both had the same outer panel sections. These differences reflected the intention to use the ITS-8 as a trainer and the ITS-8W in competitive events.[1][2]

The ITS's pilot sat under the wing leading edge in an enclosed cockpit within a drop-shaped, ply-skinned nacelle, its pointed end just aft of the trailing edge. A thin, faired structure connected the nacelle to the centre of the wing, bracing it and the engine, largely buried in the wing apart from a carefully faired air intake at mid-chord and cylinder heads exposed for cooling. The ITS-8 had a 18 hp (13 kW)* Koeber Kötter M3 flat twin engine and the ITS-8W initially used another flat-twin, the 23–36 hp (17–27 kW)* Schliha s a stop-gap, later replacing it with the intended 30–32 hp (22–24 kW)* Sarolea Albatros flat-twin. The empennage was mounted on twin rectangular section spruce box girder booms which were internally wire-braced. A tapered tailplane with rounded tips was positioned on the top of the beams. The ITS-8 had a narrow fin mounted centrally on the tailplane, carrying a large balanced rudder but on the ITS-8W this was replaced with twin fins and rudders on the booms.[1][2]

The nacelle had a sprung landing skid, a semi-retractable monowheel under the wing and a long leaf spring tailwheel. On the ITS-8W the latter was faired-in and ended with a tailwheel.[1][2]



Variants

ITS-8
First prototype.
ITS-8W
Second prototype, with more powerful engine, improved engine mounting and twin fins. Production prevented by the German invasion of Poland.
ITS-8M
Intended for meteorological research with a fully cantilver wing, flaps and twin wheel retractable landing gear but unfinished before the invasion.

Specifications (ITS-8)

Data from J. Cynk (1971)[1]

General characteristics

  • Crew: One
  • Length: 6.4 m (21 ft 0 in)
  • Wingspan: 13.6 m (44 ft 7 in)
  • Wing area: 16.9 m2 (182 sq ft)
  • Empty weight: 180 kg (397 lb)
  • Gross weight: 290 kg (639 lb)
  • Powerplant: 1 × Koeber Kötter M3 flat twin engine, 13 kW (18 hp)
  • Propellers: 2-bladed Szomański, 1.36 m (4 ft 6 in) diameter wooden

Performance

  • Maximum speed: 120 km/h (75 mph, 65 kn) at sea level
  • Cruise speed: 110 km/h (68 mph, 59 kn)
  • Service ceiling: 1,500 m (4,900 ft)
  • Rate of climb: 1.3 m/s (260 ft/min)
  • Rate of sink: 0.91 m/s (179 ft/min) engine off
  • Landing speed: 45 km/h (28 mph; 24 kn)

References

  1. ^ a b c d e Cynk, Jerzy (1971). Polish Aircraft 1893-1939. London: Putnam Publishing. p. 651-4. ISBN 0 370 00085 4.
  2. ^ a b c "ITS-8, 1936". Samolotypolskie.pl. Retrieved 13 May 2018.



Category:Twin boom aircraft Category:Pusher aircraft Category:Motor gliders Category:Polish sport aircraft 1930–1939

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