Kharkiv KhAI-4

The Kharkiv KhAI-4 was an experimental Soviet tailless aircraft tested in 1934. It only made three flights before being grounded as dangerous.

Kharkiv KhAI-4
Role experimental tailless aircraft
National origin USSR
Manufacturer Kharkovskii Aviatsionni Institut
Designer P.G. Benning, A.A. Lazarev, A.A. Krol
First flight October 1934
Number built 1

Design and development

The KhAI-4 was the Kharkov Institute's first tailless design, making its first flight two years before the Kharkov KhAI-3. It was an all-wood machine.[1]

It was rather similar in layout to the powered version of the Lippisch Delta 1, first flown three years earlier in 1931, and had similar dimensions but a much more powerful engine.[2][3] Its low-mounted wing was tetragonal in plan, with sweep (15°) only on the leading edges. Wing tip fins, which had a blunted triangular profile, carried slightly more rounded rudders. Ailerons occupied the outer 65% of each wing, with the rest filled with an elevon. The controls were essentially conventional, with rudder pedals and a wheel for the ailerons which, when pushed or pulled moved the elevons together to change pitch.[1]

Its fuselage was short but deep, with an enclosed cabin over the leading edge holding two seats in tandem. A Shvetsov M-11 radial engine, working in pusher configuration, was mounted high on the rear fuselage with its five cylinders exposed for cooling. Under the engine the fuselage was cut away.[1]

The KhAI-4 had a conventional fixed undercarriage, though the need for propeller ground clearance required a long tailwheel leg, producing a low ground angle of attack.[1]

Operational history

The first flight was piloted by B.N. Kudrin, who found insufficient elevon authority to lift the nose for take-off until he reached 180 km/h (110 mph; 97 kn), the design maximum airspeed. Pitch instability dominated the rest of the flight, though he landed successfully. Two more flights were made before the KhAI-4 was grounded as dangerous.[1]

Specifications

Data from Russian Aircraft 1875-1995[1]

General characteristics

  • Crew: two
  • Length: 4.2 m (13 ft 9 in)
  • Wingspan: 12.0 m (39 ft 4 in)
  • Wing area: 21.25 m2 (228.7 sq ft)
  • Empty weight: 550 kg (1,213 lb)
  • Gross weight: 850 kg (1,874 lb)
  • Powerplant: 1 × Shvetsov M-11 5-cylinder air-cooled radial, 93 kW (125 hp) . Sub-type not known so power uncertain.
  • Propellers: 2-bladed

Performance

  • Maximum speed: 180 km/h (110 mph, 97 kn) at sea level
  • Range: 600 km (370 mi, 320 nmi) design target
  • Service ceiling: 3,250 m (10,660 ft) estimated service ceiling
  • Landing speed: 100 km/h (62 mph; 54 kn)

References
  1. Gunston, Bill (1995). The Osprey Encyclopedia of Russian Aircraft 1875-1995. London: Osprey (Reed Consumer Books Ltd). p. 148-9. ISBN 1 85532 405 9.
  2. Bowers, Peter M. (1984). Unconventional Aircraft. Blue Ridge Summit: Tab Books Inc. p. 40-1. ISBN 0 8306 2384 1.
  3. "L'avion sans queue Lippisch, de la R.R.G." L'Aérophile. 39 (X): 299. 1–15 October 1931.


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