Kharkiv KhAI-4
| {{Infobox aircraft begin
| name=Kharkiv KhAI-4 | image=File:KN Charkov ChAi4-1937.jpg | caption= }}{{Infobox aircraft type | type=Experimental tailless aircraft | national origin=USSR | manufacturer=Kharkovskii Aviatsionni Institut | designer=P.G. Benning, A.A. Lazarev, A.A. Krol | first flight=October 1934 | primary user= | number built=1 }} |
The Kharkiv KhAI-4 was an experimental Soviet tailless aircraft tested in 1934. It only made three flights before being grounded as dangerous.
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.
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. 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.
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.
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.
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 {{cvt|180|km/h|mph 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.
Specifications
{{Aircraft specs
|ref=Russian Aircraft 1875-1995
|prime units?=met
|genhide=
|crew=two
|length m=4.2
|length note=
|span m=12.0
|span note=
|height m=
|height ft=
|height in=
|height note=
|wing area sqm=21.25
|wing area note=
|aspect ratio=
|airfoil=
|empty weight kg=550
|empty weight note=
|gross weight kg=850
|gross weight note=
|max takeoff weight kg=
|max takeoff weight lb=
|max takeoff weight note=
|fuel capacity=
|more general=
|eng1 number=1
|eng1 name=Shvetsov M-11
|eng1 type=5-cylinder air-cooled radial
|eng1 hp=125
|eng1 note=. Sub-type not known so power uncertain.
|prop blade number=2
|prop name=
|prop dia m=
|prop dia ft=
|prop dia in=
|prop dia note=
|perfhide=
|max speed kmh=180
|max speed note=at sea level
|cruise speed kmh=
|cruise speed mph=
|cruise speed kts=
|cruise speed note=
|stall speed kmh=
|stall speed mph=
|stall speed kts=
|stall speed note=
|never exceed speed kmh=
|never exceed speed mph=
|never exceed speed kts=
|never exceed speed note=
|range km=600
|range note=design target
|endurance=
|ceiling m=3250
|ceiling note=estimated service ceiling
|g limits=
|roll rate=
|glide ratio=
|climb rate ms=
|climb rate ftmin=
|climb rate note=
|time to altitude=
|sink rate ms=
|sink rate ftmin=
|sink rate note=
|lift to drag=
|wing loading kg/m2=
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|more performance=
- Landing speed: {{cvt|100|km/h|mph kn}}
}}