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Seibel S-3

With two collaborators Seibel built in 1947 the S-3 light helicopter with lateral and longitudinal control effected by changing the center of gravity.Each blade attaches to the rotor hub with the help of a piece of bent sheet metal. This formed an angle that could be “twisted” to control changes in pitch. The advantage of this design is how mechanically simple it is. There is no need for bearings, hinges or dampers.
A moveable cabin section shifted in response to "cyclic" stick inputs, thereby shifting the c/g and causing the machine to act accordingly. This was soon abandoned (insufficient control and the potential for roll-over on a hard landing) and replaced by a more conventional cyclic control system for testing and promotional flying.
S-3 NX735B c/n 1 was built in a cellar from miscellaneous spare parts, including a truck differential and an automotive clutch.
The S-3, NX735B, first took flight on 4 September 1947 and flew mainly to demonstrate Charles Seibel’s simplified two-bladed rotor system and transmission.
Most design and features evolved into the Cessna CH Skyhook.
Engine 65hp Franklin
Rotor diameter: 7.62m
Loaded weight: 365kg
Empty weight: 245kg
Cruising speed: 112km/h
Inclined climb: 275m/min
Absolute ceiling: 3660m
Seats: 1

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