Pitcairn PA-22

Pitcairn PA-22
Role	Experimental, direct contol autogyro
National origin	United States
Manufacturer	Autogiro Company of America
First flight	April 1933
Number built	1

The Pitcairn PA-22 was one of the first wingless autogyros, controlled by movement of the rotor plane rather than the usual control surfaces, though initially the much modified lone example retained rudders as a precaution.

Design and development

The first autogyros, while relying on the rotor for lift, were controlled in flight with ailerons, elevators and rudders like fixed wing aircraft. The first United States autogyro to dispense with these was the PA-22, though it initially retained the rudders. The pilot manoeuvred by altering the rotor plane by a long handle which reached down into the cabin; such designs were termed direct control autogyros. Direct control meant the aircraft could be controlled at the lowest speed at which sufficient lift was availble, rather then the higher speeds required for control surface authority. First flown in April 1933, it was first demonstrated in public in Washington D.C., on 8 November 1934.

The PA-22 had a three-bladed rotor with a diameter of 32 ft (9.8 m), pylon-mounted over the cockpit. It was connected via a clutch to the nose-mounted, 85 hp (63 kW) Pobjoy Cataract engine to spin it up at a low angle of incidence for take-off. Uncowled for cooling and driving a conventional two-bladed propeller, the Cataract powered the PA-22 conventionally once autorotation was established, in standard autogyro fashion.

Behind the engine the fuselage of the PA-22 was conventional, with two side-by-side seats in a flat-sided cabin with generous glazing including windows for both upward and downward views. Acces was via side doors. Its tail included a constant chord tailplane mounted above the fuselage which carried twin fins inboard of its rounded tips. In the early stages of this much modified airframe, the fins carried rudders as a precaution but experience of direct control allowed their removal.

The PA-22 had a split axle, fixed tailwheel undercarriage. Its design was similar to that of many fixed wing and autogyro aircraft, with the axles and their rearward drag struts mounted on the central fuselage underside. Long shock-absorbing legs are attached to the upper fuselage. The front wheels were further forward than on earlier aircraft, making the fraction of tailwheel weight greater than usual. Because there was no wing lift involved, it was not necessary to lift the tail during take-off. All three tyres were pneumatic and the tailwheel was steerable.

Another unusual feature of the PA-22 was its foldable rotor. Like other autogyros, the rotor blades were hinged to the drive shaft in the rotor lane. In flight, each blade's movement was limited to a few degrees by a pin but this could be removed and the blades folded back. With no wings, hangar space was minimized.

Variants

Autogiro AC-35

A roadable autogyro derived from the PA-22, aerodynamically similar and with a foldable rotor but with a centrally-positioned engine. This drove a tractor propeller in flight via a long drive shaft but the tailwheel on the ground.

Specifications

Data from

General characteristics

• Crew: 2
• Length: 18 ft (5.5 m)
• Empty weight: 600 lb (272 kg) approximately
• Gross weight: 1,140 lb (517 kg) approximately
• Fuel capacity: 17 US gal (14 imp gal; 64 L)
• Powerplant: 1 × Pobjoy Cataract seven cylinder radial, 85 hp (63 kW)
• Main rotor diameter: 32 ft (9.8 m)
• Propellers: 2-bladed

Performance

• Maximum speed: 105 mph (169 km/h, 91 kn)
• Cruise speed: 90 mph (140 km/h, 78 kn)
  
• Approximate minimum speed: 17 mph (27 km/h; 15 kn)
• Approximate take off speed: 25 mph (40 km/h; 22 kn)
• Range: 350 mi (560 km, 300 nmi)

References

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