Swashplate (aeronautics)
file:Taumel 142 b.png|thumb|Swashplate on a radio-controlled helicopter. 1. Non-rotating outer ring. 2. Turning inner ring. 3. Ball joint. 4. Control preventing turning of outer ring. 5. Control. 6. Linkages to the rotor blade
In aeronautics, a swashplate is a mechanical device that translates input via the helicopter flight controls into motion of the main rotor blades. Because the main rotor blades are spinning, the swashplate is used to transmit three of the pilot's commands from the non-rotating fuselage to the rotating rotor hub and mainblades.
History
The swashplate was first tested in 1907 by brothers Jules and Paul Cornu. They obtained a patent for the device. Although its principle is also found in earlier patents by other screw inventors. The first successful implementation of the swashplate was made by de la Cierva in 1922 in his autogyro.However, it is widely accepted that the swashplate was first proposed by Russian Boris Yuriev in 1911. No direct sources for this. The known helicopter mock-up did not have such a device, drawings have not survived, and no patent application has been filed.
Today, on most modern aircraft the swashplate is above the transmission and the pushrods are visible outside the fuselage, but a few early designs, notably light helicopters built by Enstrom Helicopter, placed it underneath the transmission and enclosed the rotating pushrods inside the mainshaft. This reduces rotor hub drag since there are no exposed linkages.
Other swashplate and control design have been used. For instance, Kaman Aircraft helicopters do not use a traditional swashplate and instead operate servo flaps on the rotor blades to adjust the angle of attack of the blades.
Assembly
The swashplate consists of two main parts: a stationary swashplate and a rotating swashplate. The stationary swashplate is mounted on the main rotor mast and is connected to the cyclic and collective controls by a series of pushrods. It is able to tilt in all directions and move vertically. The rotating swashplate is mounted to the stationary swashplate by means of a bearing and is allowed to rotate with the main rotor mast. An anti-rotation link prevents the inner swash from rotating independently of the blades, which would apply torque to the actuators. The outer swashplate typically has an anti-rotation slider as well to prevent it from rotating. Both swashplates tilt up and down as one unit. The rotating swashplate is connected to the pitch horns by the pitch links. Alternative mechanics to the stationary swashplate are the hexapod and the universal joint.Swashplates for helicopters having two rotors mounted on the same shaft are much more complex than the single rotor helicopters.