NOTAR

Last updated
MD Explorer air ambulance G-HAAT (35321548351).jpg
MD Explorer air ambulance

NOTAR ("no tail rotor") is a helicopter system which avoids the use of a tail rotor. It was developed by McDonnell Douglas Helicopter Systems (through their acquisition of Hughes Helicopters). The system uses a fan inside the tail boom 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 is gained through a vented, rotating drum at the end of the tailboom, called the direct jet thruster. Advocates of NOTAR assert that the system offers quieter and safer operation than a traditional tail rotor. [1]

Contents

Development

The Cierva W.9 showing the long tailboom from which the efflux from the engine-driven fan emerged from a directable vent on the left side at the tip of the tailboom Cierva W.9.jpg
The Cierva W.9 showing the long tailboom from which the efflux from the engine-driven fan emerged from a directable vent on the left side at the tip of the tailboom

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. The Fiat 7005 used a pusher propeller that blew against a cascade of tail vanes at the rear of its fuselage.

Development of the NOTAR system dates back to 1975, when engineers at Hughes Helicopters began concept development work. [2] On December 17, 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 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 Novosel, Alabama.

A production model NOTAR 520N (N520NT) was later produced and first flew on May 1, 1990. It collided with an Apache AH-64D and crashed on September 27, 1994 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, [notes 1] causing the downwash from the main rotor to hug the tail boom, 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 as tail rotors on helicopters produce much of the aircraft's sound. NOTAR-equipped helicopters are among the quietest helicopters certified by FAA. [4]

Applications

MD Helicopters 520N NOTAR Belgium Police 520N (cropped).jpg
MD Helicopters 520N NOTAR

There are several production helicopters that utilize the NOTAR system, which are produced by MD Helicopters:

See also

Notes

  1. NOTAR is an American-designed system and so this is true for American-made helicopters whose main rotors rotate counterclockwise (viewed from above). Many helicopters made elsewhere, such as France and Russia, have clockwise rotating main rotors and with the opposite resultant torque would require the slots to be on the left.

Related Research Articles

<span class="mw-page-title-main">Helicopter flight controls</span> Instruments used in helicopter flight

Helicopter flight controls are used to achieve and maintain controlled aerodynamic helicopter flight. Changes to the aircraft flight control system transmit mechanically to the rotor, producing aerodynamic effects on the rotor blades that make the helicopter move in a desired way. To tilt forward and back (pitch) or sideways (roll) requires that the controls alter the angle of attack of the main rotor blades cyclically during rotation, creating differing amounts of lift at different points in the cycle. To increase or decrease overall lift requires that the controls alter the angle of attack for all blades collectively by equal amounts at the same time, resulting in ascent, descent, acceleration and deceleration.

<span class="mw-page-title-main">Tail rotor</span> Rotor mounted on the tail of a helicopter

The tail rotor is a smaller rotor mounted vertically or near-vertically at the tail of a traditional single-rotor helicopter, where it rotates to generate a propeller-like horizontal thrust in the same direction as the main rotor's rotation. The tail rotor's position and distance from the helicopter's center of mass allow it to develop enough thrust leverage to counter the reactional torque exerted on the fuselage by the spinning of the main rotor. Without the tail rotor or other anti-torque mechanisms, the helicopter would be constantly spinning in the opposite direction of the main rotor when flying.

<span class="mw-page-title-main">Helicopter rotor</span> Aircraft component

On a helicopter, the main rotor or rotor system is the combination of several rotary wings with a control system, that generates the aerodynamic lift force that supports the weight of the helicopter, and the thrust that counteracts aerodynamic drag in forward flight. Each main rotor is mounted on a vertical mast over the top of the helicopter, as opposed to a helicopter tail rotor, which connects through a combination of drive shaft(s) and gearboxes along the tail boom. The blade pitch is typically controlled by the pilot using the helicopter flight controls. Helicopters are one example of rotary-wing aircraft (rotorcraft). The name is derived from the Greek words helix, helik-, meaning spiral; and pteron meaning wing.

<span class="mw-page-title-main">Rotorcraft</span> Heavier-than-air aircraft with rotating wings

A rotary-wing aircraft, rotorwing aircraft or rotorcraft is a heavier-than-air aircraft with rotary wings that spin around a vertical mast to generate lift. The assembly of several rotor blades mounted on a single mast is referred to as a rotor. The International Civil Aviation Organization (ICAO) defines a rotorcraft as "supported in flight by the reactions of the air on one or more rotors".

<span class="mw-page-title-main">MD Helicopters</span> American aerospace manufacturer

MD Helicopters, LLC. is an American aerospace manufacturer. It produces light utility helicopters for commercial and military use. The company was a subsidiary of Hughes Aircraft until 1984, when McDonnell Douglas acquired it and renamed it McDonnell Douglas Helicopter Systems. It later became MD Helicopters in 1999 after McDonnell Douglas merged with Boeing.

<span class="mw-page-title-main">MD Helicopters MD 500</span> Light utility helicopter family

The MD Helicopters MD 500 series is an American family of light utility civilian and military helicopters. The MD 500 was developed from the Hughes 500, a civilian version of the US Army's OH-6A Cayuse/Loach. The series currently includes the MD 500E, MD 520N, and MD 530F.

<span class="mw-page-title-main">MD Helicopters MD Explorer</span> Light twin-engine utility helicopter

The MD Helicopters MD Explorer is a light twin-engined utility helicopter designed and initially produced by the American rotorcraft specialist McDonnell Douglas Helicopter Systems.

<span class="mw-page-title-main">Helicopter</span> Type of rotorcraft

A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes allow helicopters to be used in congested or isolated areas where fixed-wing aircraft and many forms of short take-off and landing (STOL) or short take-off and vertical landing (STOVL) aircraft cannot perform without a runway.

<span class="mw-page-title-main">MD Helicopters MD 600</span> Light utility helicopter

The MD Helicopters MD 600N is a light utility civilian helicopter designed in the United States. It is a stretched eight-seat development of the five-seat MD 520N helicopter.

<span class="mw-page-title-main">Powered lift</span> VTOL capable fixed-wing aircraft

A powered lift aircraft takes off and lands vertically under engine power but uses a fixed wing for horizontal flight. Like helicopters, these aircraft do not need a long runway to take off and land, but they have a speed and performance similar to standard fixed-wing aircraft in combat or other situations.

<span class="mw-page-title-main">Cierva W.9</span> British helicopter

The Cierva W.9 was a British 1940s experimental helicopter with a three-blade tilting-hub controlled main rotor, and torque compensation achieved using a jet of air discharged from the rear port side of the fuselage. The design was not further developed into production, and the prototype crashed in 1946.

The Fiat Model 7002 was a 1960s Italian general-purpose helicopter with a tip jet driven rotor built by Fiat Aviazione. Only one aircraft was built.

<span class="mw-page-title-main">SNCASO SO.1221 Djinn</span> Type of aircraft

The Sud-Ouest SO.1221 Djinn is a French two-seat light helicopter designed and manufactured by aircraft manufacturer Sud-Ouest (SNCASO), which was later merged into Sud Aviation. It was the first production French helicopter, as well as being one of the first practical European helicopters to be produced. The Djinn was also the first rotorcraft to harness tip-jet propulsion to enter production, and the first production turbine powered helicopter.

<span class="mw-page-title-main">Monocopter</span>

A monocopter or gyropter is a rotorcraft that uses a single rotating blade. The concept is similar to the whirling helicopter seeds that fall from some trees. The name gyropter is sometimes applied to monocopters in which the entire aircraft rotates about its center of mass as it flies. The name "monocopter" has also been applied to the personal jet pack constructed by Andreas Petzoldt.

<span class="mw-page-title-main">Bell 30</span> Type of aircraft

The Bell 30 is the prototype for the first commercial helicopter, and the first helicopter built by the Bell Aircraft Company. Designed by Arthur M. Young, the type served as a demonstration testbed for the successful Bell 47.

The Nord 1750 Norelfe was a 1950s French three-seat helicopter built by Nord Aviation and designed by Jean Cantinieau.

<span class="mw-page-title-main">Dornier Do 32</span> Type of aircraft

The Dornier Do 32E was a simple, collapsible one-man helicopter, designed for military use in Germany in the 1960s. Despite initial hopes of large orders and some proposed civilian roles, only three flew.

<span class="mw-page-title-main">Matra-Cantinieau MC-101</span> Type of aircraft

The Matra-Cantinieau MC-101 was an early 1950s French experimental two seat helicopter of conventional tail rotor configuration but with its engine mounted close to the main rotor, above the seating.

The Nord 1700 Norélic or SNCAN N.1700 Norélic was a French helicopter with several novel control features. Only one prototype was built, though it was intended to lead to series production.

The SNCASE SE-3110 or Sud-Est SE-3110 was a French two seat experimental helicopter with unusual twin, angled tail rotors, first flown in 1950. After brief tests SNCASE decided to concentrate on a closely related but single-tail-rotor design.

References

  1. "NOTAR Helicopter Design". Kulikov Aircraft Design. 7 January 2000. Archived from the original on 27 May 2000.{{cite web}}: CS1 maint: unfit URL (link)
  2. 1 2 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". MD Helicopters. 2006. Archived from the original on 12 March 2007.
  4. Federal Aviation Administration. "AC 36-1H - Noise Levels for U.S. Certificated and Foreign Aircraft" . Retrieved 27 June 2022.