Tail rotor

The tail rotor of a helicopter is mounted on the tail of a traditional single-rotor helicopter, close to perpendicular to the main rotor. It is primarily used in order to counteract the yaw motion and the torque that a rapidly turning disk naturally produces. The tail rotor in simple terms is a propeller that pushes the body of the helicopter in the opposite direction of the main rotor, preventing loss of control.

ignificance

The tail rotor, stabilising the helicopter as it does, is an extremely crucial element of the helicopter, and loss or serious damage often means immediate loss of flight control, often resulting in serious and fatal crashes.

However, the loss does not "necessarily" mean all control has to be lost — if the aircraft can be kept moving in a forward direction, it can sometimes still be flown. In one case, a New Zealand helicopter pilot with extensive flight experience managed to lose his Robinson R44 helicopter's tail rotor at 4500 ft due to object strike (likely from something that had fallen from the open cabin), and then nursed the aircraft for over 25 minutes to an agricultural airstrip in Fiordland, because no other landing sites were available in the mountaineous terrain. He was forced to land at a speed of 80 knots and skidded for 45 m before coming to a rest, unharmed and with the helicopter in a repairable state. [" [http://www.nzherald.co.nz/section/1/story.cfm?c_id=1&objectid=10493099 Pilot's 'exceptional flying' saves $540,000 helicopter] " - "The New Zealand Herald", Monday 18 February 2008]

Design variations

There are two major variations to traditional tail rotor design concerning the placement of the tail rotor and the surrounding structure. Some companies such as Eurocopter enclose the rotor within a fantail assembly. Such design - called fenestron - protects the tail rotor from foreign object damage better than the traditional outer mounted design but complicates the design of the tailcone to account for the enclosed mechanisms.

New developments

In some more recent helicopter designs, the tail rotor has been mounted tangential to the furthest back point of the top rotor. That is to say that it looks much like an old propeller plane, only at the back of the helicopter instead of the front of a wing. In these new designs the rotor spins in a direction opposite to the top rotor (i.e. counter-clockwise if the rotor spins clockwise and vise-versa). This in effect, cancels the spin and has the added benefit of producing forward thrust. Fact|date=February 2007

Most, if not all, dual-rotary helicopters do not use tail rotors, instead, the design of the two main rotors is such that they spin in the opposite directions of each other, thus each cancels out the torque and yaw produced by the other. This has been researched in the past and has been incorporated into some European designs.

Sikorsky Aircraft, a UTC subsidiary is currently researching the merger of these two concepts with a dual rotor helicopter with a rear rotor to provide additional forward thrust and a respective increase in speed and operating range. First flight of a prototype aircraft, the Sikorsky X2 Demonstrator is expected to be accomplished by the end of 2006

ee also

*Fenestron
*NOTAR

References