NOTAR: Anti-Torque System
Intro to Aircraft Systems
February 4, 2013
All single rotor helicopters need some way to counteract the torque that is created by the rotor blades spinning around the mast. The most common anti-torque system used on helicopters is the Tail Rotor System. The Tail Rotor System is a relatively small rotor and transmission attached at the end of the tail boom that is driven from a shaft coming from the main engine and transmission (ASA, Helicopter Flying Handbook 1-5). Another anti-thrust system used less frequently is the Fenestron system. It is driven in a similar way to the standard tail rotor system but instead of two rotor blades at the end of the boom there is a series of rotating blades that are enclosed in a protective shroud, thus adding a degree in safety by protecting the tail rotor blades from ground contact (ASA, Helicopter Flying Handbook 4-7). The anti-torque system I want to discuss in greater detail is called the “NOTAR” system. The NOTAR system is dramatically different in design as it does not require another rotor at the end of the tail boom to create thrust and in losing that tail rotor this system has a number of advantages, added safety being one of the crucial benefits. The NOTAR system uses the natural characteristics of aerodynamics along with thrust from pressurized air exiting the tail boom to provide the thrust needed to counter the torque being produced by the main rotor (ASA, Helicopter Flying Handbook 4-7). It does this using the following components that are built into the design of the helicopter: air intake, fan, tail boom the can contain and control airflow, tail thruster cone, and two vertical stabilizers at the end of the tail boom. The first component of this system is the air intake, or a large opening on top of the rear fuselage. This intake is covered by a fine mesh screen designed to keep foreign objects from getting sucked into the system (Wagtendonk 190). The intake pulls air...
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