NOTAR - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/NOTAR

NOTAR From Wikipedia, the free encyclopedia

NOTAR is the name of a anti-torque system which replaces the use of a . NOTAR Developed by McDonnell Douglas Helicopter Systems (through their acquisition of Hughes ), the name is an acronym derived from the phrase no tail rotor. The system uses a fan inside the tailboom to build a high volume of low-pressure air, which exits through two slots and creates a boundary layer flow of air along the tailboom utilizing the Coandă effect. The boundary layer changes the direction of airflow around the tailboom, creating thrust opposite the motion imparted to the fuselage by the torque effect of the main rotor. Directional yaw control MD Explorer (German police) is gained through a vented, rotating drum at the end of the tailboom, called the direct jet thruster. Advocates of NOTAR believe the system offers quieter and safer operation.[1]

Contents

1 Development 2 Concept 3 Applications 4 See also 5 References 6 External links

Development

The use of directed air to provide anti-torque control had been tested as early as 1945 in the British Cierva W.9. During 1957, a Spanish prototype designed and built by Aerotecnica flew using exhaust gases from the turbine instead of a tail rotor. This model was designated as Aerotecnica AC-14. Development of the NOTAR system dates back to 1975, when engineers at began concept development work.[2] In December 1981, Hughes flew an OH-6A fitted with NOTAR for the first time. The OH-6A helicopter (serial number 65-12917) was supplied by the U.S. The Cierva W.9 showing the long Army for Hughes to develop the NOTAR technology and was tailboom from-which the efflux from the second OH-6 built by Hughes for the U.S. Army. A more the engine-driven fan emerged from a

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heavily modified version of the prototype demonstrator first directable vent on the left side at the flew in March 1986 (by which time McDonnell Douglas had tip of the tailboom acquired Hughes Helicopters). The original prototype last flew in June 1986 and is now at the U.S. Army Aviation Museum in Fort Rucker, Alabama. Soviet manufacturer Kamov made a prototype on their co-axial helicopter Ka-26 which they called Ka-26SS in 1988 it never went into production.

A production model NOTAR 520N (N520NT) was later produced and first flew on May 1, 1990. It later crashed on September 27, 1994 when it collided with an AH-64D while flying as a chase aircraft for the Apache. Concept

Although the concept took over three years to refine, the NOTAR system is simple in theory and works to provide some directional control using the Coandă effect.[2] [3] 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. Diagram showing the movement of air through the NOTAR system. Benefits of the NOTAR system include increased safety (the tail rotor being vulnerable), and greatly reduced external noise. NOTAR-equipped helicopters are among the quietest certified helicopters. Applications

There are three production helicopters that utilize the NOTAR system, all produced by MD Helicopters:

MD 520N - a NOTAR variant of the Hughes/MD500 series helicopter. MD 600N - a larger version of the MD 520N. 1 Air intake 2 Variable pitch fan 3 MD Explorer - a twin-engine, 8-seat light helicopter. Tail boom with Coandă Slots 4 Vertical stabilizers 5 Direct jet See also thruster 6 Downwash 7 Circulation control tailboom cross-section 8 Cierva-Weir W.9 Anti-torque lift Helicopter Tail rotor Other alternatives to conventional tail rotor Fenestron Tip jet rotor Coaxial rotors

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Tandem rotors Synchropter References

1. ^ kulikovair.com (http://www.kulikovair.com/Notar.htm) MD 900 2. ^ a b Frawley, Gerard: The International Directory of Civil Aircraft, 2003-2004, page 155. Aerospace Publications Pty Ltd, 2003. ISBN 1-875671-58-7 3. ^ NOTAR Technology (http://www.mdhelicopters.com /products.php?id=NOTAR) External links

MD Helicopters (http://www.mdhelicopters.com /products.php?id=NOTAR) Youngcopter (http://www.youngcopter.com/) , manufacturer of the neo - a kit helicopter with Wankel Aerotécnical AC-14, Ducted exhaust engine and NOTAR-like anti-torque system. and rudders detail

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