NOTAR

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MD 900 (German police)

NOTAR, an acronym for NO TAil Rotor, is a helicopter stabilization process developed by McDonnell Douglas Helicopter Systems which eliminates the use of tail rotors on helicopters, yielding quieter and safer operation.

Development of the revolutionary NOTAR system dates back to late 1975 when engineers at Hughes Helicopters began initial concept development work.^[1] In December 1981 Hughes flew a OH-6A fitted with NOTAR for the first time. A more heavily modified prototype demonstrator first flew in March 1986 (by which time McDonnell Douglas had acquired Hughes).

Although the concept, which uses the Coandă effect, took some time to refine, the NOTAR system is simple in theory and works to provide directional control the same way a wing develops lift.^[1] A variable pitch fan is enclosed in the aft fuselage section immediately forward of the tail boom and driven by the main rotor transmission. This fan forces low pressure air through two slots on the right side of the tailboom, causing the downwash from the main rotor to hug the tailboom, producing lift, and thus a measure of directional control. This is augmented by a direct jet thruster and vertical stabilisers. NOTAR system benefits include far lower external noise (NOTAR-equipped helicopters are among the quietest certificated helicopters in the world), increased safety due to the lack of a tail rotor, improved handling and performance, reduced vibration and easier maintainability.

There are currently three helicopters that take advantage of NOTAR technology, all produced by MD Helicopters:

MD 520N - a NOTAR variant of the Hughes/MD500 series helicopter is seen in the movie Mission: Impossible
MD 600N - a larger version of the MD 520N, is seen in the James Bond film Die Another Day
MD 902 Explorer - a twin-engine, 8-seat light helicopter.