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NOTAR
MD Explorer (German police)
The Cierva W.9 showing the long
tailboom from-which the efflux from
the engine-driven fan emerged from a
NOTARFrom Wikipedia, the free encyclopedia
NOTAR is the name of a helicopter anti-torque
system which replaces the use of a tail rotor.
Developed by McDonnell Douglas Helicopter
Systems (through their acquisition of Hughes
Helicopters), 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 Coand 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 controlis 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 Concept3 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. During1957, 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 Hughes Helicopters 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.
Army for Hughes to develop the NOTAR technology and was
the second OH-6 built by Hughes for the U.S. Army. A more
NOTAR - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/NOTAR
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directable vent on the left side at the
tip of the tailboom
Diagram showing the movement of
air through the NOTAR system.
1 Air intake 2 Variable pitch fan 3
Tail boom with Coand Slots 4
Vertical stabilizers 5 Direct jet
thruster 6 Downwash 7 Circulation
control tailboom cross-section 8
Anti-torque lift
heavily modified version of the prototype demonstrator first
flew in March 1986 (by which time McDonnell Douglas had
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 Coand effect.[2]
[3]
A
variable pitch fan is enclosed in the aft fuselage sectionimmediately 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.
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.
MD Explorer - a twin-engine, 8-seat light helicopter.
See also
Cierva-Weir W.9
Helicopter
Tail rotor
Other alternatives to conventional tail rotor
Fenestron
Tip jet rotor
Coaxial rotors
NOTAR - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/NOTAR
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MD 900
Aerotcnical AC-14, Ducted exhaust
and rudders detail
MD Helicopters 520N NOTAR
Tandem rotors
Synchropter
References
^ kulikovair.com (http://www.kulikovair.com/Notar.htm)1.
^ ab Frawley, Gerard: The International Directory of CivilAircraft, 2003-2004, page 155. Aerospace Publications PtyLtd, 2003. ISBN 1-875671-58-7
2.
^ NOTAR Technology (http://www.mdhelicopters.com/products.php?id=NOTAR)
3.
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
engine and NOTAR-like anti-torque system.
Retrieved from "http://en.wikipedia.org
/w/index.php?title=NOTAR&oldid=476970480"
Categories: Aerospace engineering
Helicopter components
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