199?-project  An SAAF Alouette III technology demonstration helicopter
equipped with a new tailboom without a conventional tailrotor or a fenestron was
shown by Denel Aviation. The project is known as Cirstel (Combined InfraRed
Suppression and Tail rotor Elimination). Initial research and development
workbegan in 1987 and construction of the prototype started in 1993. The
demonstrator is due to make its maiden flight "in the next few months,"
according to project engineer Nols Fonternel. The workwas conducted by Denel
under an SAAF technology contract. It was administered by Armscor. While Cirstel
has some similarities to the McDonnell Douglas NOTAR (NO Tail Rotor) system, it
is a different design, Fonternel said. Although, like NOTAR, it uses the Coanda
effect of the engine bleed-air to eliminate the need for a tail rotor while also
incorporating suppression of the exhaust's infrared signature. The Cirstel
principle splits the high pressure air from the enginefor use in the Coanda
slots, while the low pressure air is bled-off for the tail thruster and to mix
and cool the engine exhaust. The thruster nozzle is a Denel-patented clamshell
design, unlike McDonnell Douglas' `rotating can' concept. Denel intends "to
apply the Cirstel to a new helicopter design, to be developed - hopefully - with
a new partner," Fonternel said. Jane's Defence Weekly, 1996  The Denel developed Cirstel (Combined Infrared Suppression and Tail Rotor), along with Armscor and the CSIR. The Cirstel is an anti-torque system, without tail rotor mixing hot and cold air and reduces the IR signature. The program started in 1987 and was tested for 8 years from 1993. It was made from the conversion of an Alouette III. The tail was replaced by another without conventional rotor. It uses the Coanda effect air from the engine to eliminate the need for tail rotor. The air is mixed and the temperature decreases to 150 degrees.    |
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