Engine Pobjoy Ni Agra Hp

Rotorhead Pitcairn

Rotor head for Pitcairn PA-22. The hose going from the center of the hub allows hydraulic fluid to operate a cylinder which decreases the rotor pitch for run-up and suddenly increases itf0 "jump lake-off." Each blade will have a cylinder and a hose from the hub when complete. (Pitcairn Photo)

Rotor head for Pitcairn PA-22. The hose going from the center of the hub allows hydraulic fluid to operate a cylinder which decreases the rotor pitch for run-up and suddenly increases itf0 "jump lake-off." Each blade will have a cylinder and a hose from the hub when complete. (Pitcairn Photo)

throttle all the way and lifting off after a very short ground run. The engine could not be used to power the rotor during takeoff because an anti-torque device would be needed to prevent the fuselage from turning in the opposite direction as the rotor due to engine torque.

The fuselage was made from gas welded steel tubes of varying diameters and wall thicknesses. It was fabric covered with the exception of the generous allocation of transparent material around the cockpit.

Because the rotor provided all the lift and all the longitudinal and lateral control, wings were not necessary. A small rudder on the rear of the fuselage would tighten the turning radius, however, turns would be made in either direction by merely rolling into a left or right bank

Blades were similar to earlier models but the droop and interblade cables were no longer necessary due to improvements in blade design and construction.

The smaller autogiro was a test bed for many ideas—-the landing gear, tail and rotor system took on many shapes. At one time, a single large wheel was used under the center of the fuselage with small castering wheels forward. The rotor, at one time had hinges near the center of rotation as well as about half way between the blade root and the tip. Apparently this idea did not offer enough improvement in performance or rotor smoothness to justify the expense of manufacturing the double hinged blades. Specifications were as follows:

Specifications

Gross weight Empty weight Top speed Cruise speed Landing speed

1140 lbs. 600 lbs. 107 mph 90 mph 0 mph

Pobjoy Engine

Pitcairn PA-22 with blades folded for storage.

(Pitcairn Photo)

Pitcairn PA-22 with blades folded for storage.

(Pitcairn Photo)

Pobjoy Engine

1935 Pitcairn Observation Autogiro PA-33 Army YG-2.

(Pitcairn Photo)

These autogiros were similar to each other in nearly all appearances except the landing gear.

There had been a persistent rumor that the PA-33 and PA-34 were greatly modified XO-P-1 and YG-1 autogiros which were returned to Pitcairn for this rework.

During a search of the archives for more pictures of the YG-2 and XOP-2 autogiros a picture of the fuselage skeleton for the XOP-2 was uncovered. It could easily be seen that there was no resemblance of the XOP-1 (PCA-2) totheXOP-1 skeleton.

The design differences between the earlier Pitcairn-builtArmyand Navy autogiros were: A direct control rotor system using only three blades with fifty-foot diameter and absence of all the supporting and interblade wires. The engine was a Wright R-975 producing 450 hp turning a Hamilton Standard two-position propeller. A full N.A.C.A. cowl was used over the engine for cooling. A rotor pylon similar to the one used on the PA-18 was installed, having two large-diameter tubes on the fuselage centerline, braced to the upper longerons with streamlined tie rods. Gross weight was increased to 3300 lbs.

Two XOP-2s were delivered to the US Navy and the Army Air Corps purchased one YG-2. The only difference in the two models seems to be the landing gear.

The rumor may have belonged to the PA-39s which were made from PA-18s.

Pttcairn PA-34 (XOP-2) Navy autogiro. The same as PA-34 (YG-2) except landing gear. (National Archives Photo)
90hp Planetary Gearbox
Pitcairn PA-34 Navy XOP-2 Autogiro. (Pitcairn Photo)
Pitcairn Xop BlueprintsPitcairn Autogiro

Pitcairn PA-33 (YG-2) Autopro. (pücairn photo)

Pitcairn Autogiro

Pitcairn PA-33 Navy XOP-2.

(Pitcairn Photo)

Pitcairn Xop

Pitcairn PA-33 (YG-2). Note pitot-static tube at rotor head, different landing gear.

(Pitcairn Photo)

90hp Planetary Gearbox90hp Planetary Gearbox

Pitcairn PA-35 {or AC-35)

Pobjoy Engine

Pitcaim's AC-35 with Jim Ray in cockpit running tests on front wheel steering. Pobjvy "Niagra" engine can be Seen behi/id cockpit.

(Pitcairn Photo)

90hp Planetary Gearbox

In 1936 the U.S. Bureau of Air Commerce bought a two-placed autogiro; this too used a Pobjoy "Niagra" 90 hp engine.

In order to give the occupants more forward visibility, the engine was mounted just behind the seats with a shaft running through the cabin to the propeller on the nose. With this unorthodox engine installation, it was necessary to fan-cooi the engine as all piston engines in helicopters are now cooled. The engine could also be connected to the rear wheel to drive the autogiro along the road with the rotor blades folded back over the tail and the propeller disconnected from the engine. This craft can now be seen in the National Air Museum's Silver Hill Facility or as it is properly know, "The Paul E. Garber Facility." There was some confusion as to the proper model number being called the PA-35 or the AC-35.

Pitcaim AC-35 eontrarotating propellers can be seen clearly. Pobjoy "Niagra"90 hp tuns the engine mounted aft and was fan cooled. (Pitcaim Photo)

Autogiro GyroplaneGravity Engines Free Energy
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