Little-known postwar U.S. rotorcraft prototypes

[Stargazer]

When I started the topics on pre-war and post-war aircraft one-offs, my intention was always to start the corresponding rotorcraft topics... So here is the postwar "one-off" thread at last!

Let's begin with the Aeronautical Products A-1 [NX1270].

This was designed by Corwin Denny and Karl Schakel, two undergraduate engineers of the University of Michigan when they were working for the Aeronautical Products Corporation in Detroit. Although they soon left the company, Aeronautical Products Inc. — which normally manufactured aircraft engine parts — continued to work on the helicopter design they had initiated.

Built of welded-steel tubular construction, the Denny and Schakel helicopter was a single-seater with enclosed cabin, employing an auxiliary tail rotor for torque correction. The main rotor was 9m in diameter and was powered by a 90 hp engine. The gross weight of the craft was reported to be approximately 540 kg. It had a fixed tricycle landing gear. The pilot sits behind the engine, which is mounted in the nose. A long shaft extends under the pilot's seat and is geared to the vertical shaft of the rotor.

The aircraft was damaged during preparations for the first trial flights, but it was rebuilt and eventually flew successfully. It was not, however, actually put into production.

Sources:

• H. F. Gregory "Anything a Horse Can Do. The story of the Helicopter", 1944

 

[Stargazer]

A second prototype based on Denny and Shakel's design, was also produced. It was a two-seater designated as the Model 3 [NX1272] and powered by a 165 hp Franklin 6AC-298 engine. This helicopter's fuselage, of fabric-covered welded steel tubing, resembled that of a light aircraft with the engine located in the forward section and placed horizontally forward of the cabin instead of being situated centrally, as in most helicopters.

Power from the engine, cooled by a fan mounted directly above it, was transmitted by pulleys and vee belts to a horizontal main drive shaft, then through a bevel gear drive to the main rotor shaft which passed between the pilot's and the passenger's seats. Mounted on the vertical rotor drive shaft was the main gearbox for the tail shaft operating the two-bladed anti-torque rotor, with a diameter of 1.71 metres, the pitch of which was controlled by rudder pedals. This rotor's maximum rotational speed was 1200 r.p.m.

The main rotor's diameter was 9.14 m. The three blades of the main rotor were made with tapered tubular spars and also connected to the root spars by a double-action hydraulic shock absorber. Cyclic pitch control was obtained by a hanging stick while on the engine throttle support was the collective pitch control. Fully loaded, the helicopter weighed 544 kg.

The Model 3 was not put into production, and in 1947 Aeronautical Products merged with the McQuay Company.


Source:

• P.Lambermont "Helicopters and Autogyros of the World", 1958

 

[Stargazer]

The Filper helicopters already have a page, so I transfered RAP's post to the appropriate topic:
https://www.secretprojects.co.uk/forum/index.php/topic,15141.0/all.html

 

[RAP]

Thanks Skyblazer.