This was a sever problem encountered by helicopter pioneers since many didn’t realize how much the rotor blades flapped during flight and if insufficient spacing between the two rotor disks was used there could be a collision in flight. (The primary method used to control yaw was to increase collective on one rotor or the other which caused torque on the airframe in the desired direction).īlade interference. This reversal is caused by differential collective when changing from power to autorotation modes. When collective is reduced significantly in a coaxial rotor helicopter, rudder pedal action is reversed. Most helicopters utilize the conventional swash plate and coupling the joystick to the swash plate system of two rotors rotating in opposite directions increased the complexity and reduced reliability.Ĭontrol reversal at partial power.
The positive features of the coaxial rotor helicopter led early pioneers to select that design, but there were also some disadvantages that discouraged helicopter companies from producing such a configuration.Ĭomplexity of the control system. In hover the lift force is purely vertical – there is no side force generated due to the absence of the tail rotor. There is no dissymmetry of lift in forward flight since there are always advancing and retreating blades on both sides of the airframe at the same time. There is no torque on the airframe since the rotors rotate in opposite directions and therefore, no power-robbing tail rotor is required. Simplicity short couplings from the engine to the power train, and the airframe can be very compact and lighter weight than conventional designs. There are several advantages to the coaxial design, but U/S manufacturers tended to stick to the conventional single rotor with tail rotor except for Kaaman which produced an inter-meshing rotor design, and Piasecki and Boeing which have produced tandem rotor ships.Īdvantages of the coaxial rotor helicopter are: The main difference was that it utilized counter-rotating, coaxial rotors.Ĭoaxial rotors is a configuration that has never been applied to a production helicopter in this country, although Igor Sikorsky built a coaxial design before he immigrated to the U.S. The Little Zipster design included new concepts that departed from the normal helicopter, but the ship supposedly flew well in spite of the fact that it did not confirm to traditional helicopter configurations. Igor Bensen Coaxial Little Zipster Helicopter Plans and kits were offered in the late fifties, but we have not heard of anyone who built and flew one, although the prototype did fly as illustrated by the included photos from an original Bensen information pack. The “Little Zipster” was a simple coaxial design which utilized construction methods and components from the Gyrocopter.
A large tailfin provided directional stability, and the aircraft was controlled by a handlebar system extending over the pilot’s head to the rotor hub.”ĭr Igor Bensen, inventor of the “Gyrocopter” developed a number of rotary wing configurations, one of which was a coaxial rotor helicopter. Similar in general configuration to Bensen’s previous rotor kite and autogyro designs, it consisted of an open aluminum framework but substituted the autorotating main rotor for a coaxial, counter-rotating system of two, two-bladed rotors. “The Bensen B-9 Little Zipster was a small helicopter developed by Igor Bensen in the United States in the 1950s and marketed for home building.
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Bensen B9 Little Zipster Helicopter – From Wikipedia, the free encyclopedia.
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