Fenestron
Encyclopedia
Tail rotor
The tail rotor, or anti-torque rotor, is a smaller rotor mounted so that it rotates vertically or near-vertically at the end of the tail of a traditional single-rotor helicopter. The tail rotor's position and distance from the center of gravity allow it to develop thrust in the same direction as...
of a helicopter
Helicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by one or more engine-driven rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally...
that is essentially a ducted fan
Ducted fan
A ducted fan is a propulsion arrangement whereby a fan, which is a type of propeller, is mounted within a cylindrical shroud or duct. The duct reduces losses in thrust from the tip vortices of the fan, and varying the cross-section of the duct allows the designer to advantageously affect the...
. The housing is integral with the tail skin, and, like the conventional tail rotor it replaces, is intended to counteract the torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....
of the main rotor. It was originally conceived by Sud Aviation
Sud Aviation
Sud-Aviation was a French state-owned aircraft manufacturer, originating from the merger of Sud-Est and Sud-Ouest on March 1, 1957...
(now Eurocopter, part of the European Aeronautic Defence and Space Company (EADS)
EADS
The European Aeronautic Defence and Space Company N.V. is a global pan-European aerospace and defence corporation and a leading defence and military contractor worldwide...
).
While conventional tail rotors typically have two or four blades, Fenestrons have between eight and 18 blades. These may have variable angular spacing, so that the noise is distributed over different frequencies and thus sounds quieter. The housing allows a higher rotational speed than a conventional rotor, allowing it to have smaller blades.
The term Fenestron is a trademark of Eurocopter. It comes from the modern French
French language
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...
for a small window, and is ultimately from the Latin fenestra ("window")
History
The Fenestron was developed, conceived and produced to replace the classic tail rotor to improve security and performance for rotorcraft, and was used for the first time at the end of the 1960s on the second experimental model of the SA 340 by Sud AviationSud Aviation
Sud-Aviation was a French state-owned aircraft manufacturer, originating from the merger of Sud-Est and Sud-Ouest on March 1, 1957...
, and on the later model Aérospatiale SA 341 Gazelle
Aérospatiale Gazelle
The Aérospatiale Gazelle is a five-seat light helicopter, powered by a single turbine engine. It was designed and manufactured in France by Sud Aviation . It was also manufactured under licence by Westland Aircraft in the United Kingdom , by SOKO in Yugoslavia and ABHCO in Egypt...
SA341/342.
Since Sud Aviation was merged into Aérospatiale
Aérospatiale
Aérospatiale was a French aerospace manufacturer that built both civilian and military aircraft, rockets and satellites. It was originally known as Société Nationale Industrielle Aérospatiale...
, and more recently to Eurocopter, many rotorcraft in the world use the Fenestron as tail rotor, for light, intermediate and medium weight helicopters.
The Fenestron can be found on many Eurocopter helicopters, like the Eurocopter EC120 Colibri, EC130 ECO Star, EC135
Eurocopter EC135
The Eurocopter EC135 is a twin-engine civil helicopter produced by Eurocopter, widely used amongst police and ambulance services and for executive transport. It is capable of flight under instrument flight rules .-Development:...
(and EC635 the military version of the EC135), the AS365 N/N3 Dolphin
Eurocopter Dauphin
The Eurocopter SA 365/AS365 Dauphin 2 is a medium-weight multipurpose twin-engine helicopter manufactured by Eurocopter .-Design and development:...
(also known as the HH-65C widely used by the United States Coast Guard
United States Coast Guard
The United States Coast Guard is a branch of the United States Armed Forces and one of the seven U.S. uniformed services. The Coast Guard is a maritime, military, multi-mission service unique among the military branches for having a maritime law enforcement mission and a federal regulatory agency...
), the EC155 Super Dolphin (a wider, heavier and more advanced version of the AS365 N/N3 series of the Dolphin Helicopter), and more recently on the small reciprocating engine powered Guimbal Cabri G2
Guimbal Cabri G2
|-See also:-References:* -External links:* * * * *...
.
Other than Eurocopter and its predecessors, a fenestron was also used on the U.S. Boeing/Sikorsky RAH-66 Comanche, which was canceled in 2004. Ducted fan tail rotors have also been used in the Russian Kamov Ka-60
Kamov Ka-60
|-See also:-References:* Jackson, Paul. Jane's All The World's Aircraft 2003–2004. Coulsdon, UK:Jane's Information Group, 2003. ISBN 0-7106-2537-5.* "Nezavisimaya Gazeta", №241 , 25 December 1998. -External links:...
, and also on the military Japanese helicopter, the Kawasaki OH-1 Ninja.
Advantages
- Increased safetySafetySafety is the state of being "safe" , the condition of being protected against physical, social, spiritual, financial, political, emotional, occupational, psychological, educational or other types or consequences of failure, damage, error, accidents, harm or any other event which could be...
for people on the ground. The smaller size allows it to be higher above people or objects on the ground, and the enclosure provides peripheral protection; - Less susceptible to foreign object damageForeign object damageForeign Object Debris is a substance, debris or article alien to a vehicle or system which would potentially cause damage.Foreign Object Damage is any damage attributed to a foreign object that can be expressed in physical or economic terms that may or may not degrade the product's required...
. The higher ground clearance and the enclosure also makes it less likely to strike foreign objects or to suck in loose objects such as small rocks; - Greatly reduced noise and vibration, due to the enclosure of the blade tips and the greater number of blades;
- Enhanced anti-torque control efficiency;
- Reduced power demand in forward flight
Disadvantages
The Fenestron's disadvantages are those common to all ducted fanDucted fan
A ducted fan is a propulsion arrangement whereby a fan, which is a type of propeller, is mounted within a cylindrical shroud or duct. The duct reduces losses in thrust from the tip vortices of the fan, and varying the cross-section of the duct allows the designer to advantageously affect the...
s when compared to propellers. They include:
- Higher weight and air resistance of the enclosure
- Higher construction and purchasing cost
- Higher power requirement for a given thrust
- Less tail rotor authority in crosswind situations
- Limits on aircraft size
- Alleged Fenestron stall phenomenon