Pitcairn OP-1
The Pitcairn OP-1 (manufacturer designation: PCA-2) was the first rotary-wing aircraft to be seriously evaluated by any of the world's major air forces. The machine was not a helicopter, nor an airplane, but an autogyro. Pitcairn's model was never put into production for any military. Development
The Pitcairn-Cierva Autogiro Company, established by Harold Frederick Pitcairn, designed the PCA-2 based on the autogiros of Juan de la Cierva. The resulting design had a standard aircraft fuselage and powerplant, with a standard tail. However, it sported short, stubby wings, angled up at the wingtips. Above the cockpit was the rotor, consisting of three blades. The engine usually drove a standard propeller, on a vertical plane, in front of the aircraft. However, the engine could be geared to the horizontal rotor during takeoff or landing. The horizontal rotor, while in flight, did not draw energy from the engine but rather generated lift from airspeed. A minimum speed of 30 mph was needed to keep the aircraft in flight. Thus, in moderate winds, the aircraft could behave like a helicopter, except that it could not hover. The Pitcairn autogyro was first evaluated by the US military in the 1930s. In 1931, the Navy tested two prototypes, labelled XOP-1. One was tested with the aircraft carrier , on September 23, 1931. The only Pitcairn to see operational service did so in Nicaragua with the US Marines, starting in June 1932. This stint led to the Pitcairn OP-1 being rejected. Pitcairn OP-2
In 1935 the USN acquired a Pitcairn PA-34 autogyro, designated OP-2. The PA-34 was not a PCA-2 with wings removed but a separate design incorporating a three-bladed rotor with no wings, closely related to the US Army's YG-2 / PA-33. Operational service

Only the Pitcairn OP-1 saw operational service. One autogyro, assigned to Marine Utility Squadron Six (VJ-6M), was sent to Nicaragua in June 1932. The autogyro would be tested through policing the rebel-infested mountains and jungles. While the aircraft performed well, its range significantly impaired it. In addition, after the crew only 50 pounds could be carried. Marine historian Robert Debs Heinl, Jr. recounted the autogyro as being an "exasperating contraption". Operators

 United States Marine Corps
 Marine Observation Squadron 6

Specifications (OP-1)

References

Further reading
 

1930s United States military reconnaissance aircraft
OP-1
Single-engined tractor autogyros
Aircraft first flown in 1932