Last update: 12-01-2010
Cirstel, the South-African NOTAR
In spring 1996 the first reports of the South African project came into the news. At the Flight Test Centre of the Atlas Factory (a Denel Aviation Company) an Allouette III (registration 618, type SA318B, s/n: 1625) was conferted with a high tailbeam. The development was started in 1987 and called "Cirstel", Combined InfraRed Suppression and Tail Rotor Elimination. The project was proven in real scale model, the Alouette III, from 1993 for a period of 8 years.
The difference between the MD-Helicopter concept and this one is that the exhaust gases let true the tail beam to control directional movements in place of a tail rotor. This technique also reduces the infrared visability. Also the air outlet was reduced by 150 degrees. This was the result of mixing the exhaust gases with air in the tail beam. The Alouette III is used as Technology Demonstrator and testbed. The maiden (hovering) flight of the Cirstel project toke somewhere in 1996 place. November 1996 the project was demonstrated to the public. No flight tests have been completed as of 2002.
The research is still going on. In June 2003 the Departement of Mechanical Engineering (University in South Africa) descrips in a newsletter about the prototype of a two stage fan.
The two sections of the system, namely the Coanda section (compensating down wash) and the tail thruster sections (stearing), are separated from each other, which allows for optimisation of each section without compromising the other section. Each of the two sections requires a certain amount of air, supplied at a specific pressure, to function optimally. By using two fans the weight could be a problem by a helicopter design. Therefore the Departement of Mechanical Engineering made a scale model of a new fan. Extensive measurements have been conducted and the performance figures proved the concept since the design targets on which the experiments have been reached or exceeded.
The second part of the project was the Airintake for the fan.Computational Fluid Dynamics (CFD) simulations have been conducted on the intake concepts developed. In these CFD simulations the performance of the intake has been evaluated from hover through to high-speed flight. From the simulation results the intake geometry was modified to result in a serviceable design.