The Philadelphia based Autogyro Corporation of America’s Pitcairn AC 35 became a familiar sight both on and over Pennsylvania highways in the mid 1930s. Extensive road and air testing of the Pitcairn was financed by the US Bureau of Air Commerce, who thought it might be employed on Philadelphia’s autogiro operated air¬borne mail service. The AC 35 was a two-seater with a 135 hp engine mounted behind the cabin driving a pair of propellers on a common shaft up front. That was replaced by a single prop after the noise level proved to be excessive. Motor, driving the propeller by a long shaft, was buried in the fuselage behind the cabin; power was transferred to a large, steerable tail wheel for driving on the ground.
Changes to the rear control surfaces are noted in Peter W Brooks’ Cierva Autogiros: The Development of Rotary-Wing Flight (Smithsonian Press 1988) as necessary to improve longitudinal stability when the coaxial props were replaced by a single prop. The engine is also confirmed as a 90hp Pobjoy Cascade, which is corroborated by the NASM webpage article on their AC-35 exhibit. Confusion about the dates occurred because the AC-35 was flown to Washington on 2 Oct 1936, but not actually delivered there until 26 Oct 1936 for a staged handover to DoC.
As for the steering, the NASM webpage says, “For road use the rotor blades could be folded back over the fuselage, the propeller disengaged, and the tailwheel put in gear. The front wheels were used for steering.” In a picture on the Roadable Times website one can see the steering knuckles and the track rods in front of the landing gear cross-bracing.
Tested between 1936 and 1942, not only was it ingenious, it actually worked quite well, but the Pitcairn AC 35 never went into production. In 1960 Skyway Engineering announced ambitious plans for mass production of a revamped AC 35, but like its predecessor, the project was still¬born.
The Skyway Engr Co of 1964 produced an update of the Autogiro AC-35 with a 210hp Continental engine.
Year: 1937
Seats: 2
Engine: Pobjoy Niagra, 90 hp
Gross wt: 1350 lb
Rotor dia: 34 ft 3.5 in
No of blades: 3
Skyway AC-35
Engine: 210hp Continental
Projected data
Rotor diameter: 38’0″
Length: 18’11”
Useful load: 576 lb
Max speed: 134 nph
Cruise: 113 mph
Range: 400 mi
Seats: 2
All Aero 