|
Belgium (Europe) is not known for its aerospace industry. However, there are now three different manufacturers of (very) light helicopters active in the country: Dynali, Winner and, most recently (2013), Sagita, which revealed a mock-up of its Sherpa very light helicopter at Le Bourget Air Show in France. Sagita was founded in 2008 by Hubert Antoine and is located in Wallonia, the French-speaking region of Belgium. The Sherpa helicopter was developed in a consortium with four other companies and the universities of Liege and Brussels. The Sherpa is a two-seater, coaxial helicopter, but that is where the similarities with conventional coaxial machines end. Sagita took a radically different approach when it designed the dynamic system and engine in an attempt to optimize the efficiency of the transmission system while limiting the number of moving parts. The result is the patented TDR rotor drive system (patent N°EP1990275). This system uses two conventional piston engines to power the helicopter. However, it doesn’t do this by driving a conventional transmission system with belts and/or gears. Instead, the piston engines power a centrifugal air compressor and the compressed air is ducted to the rotorhead. Along the way, the combustion exhaust gases of the piston engines are used to heat the compressed airflow, adding additional power. Finally, the heated airflow drives two contra-rotating turbines that are part of the enclosed rotorhead, where they drive the rotors directly. The expanded air leaves the turbines in the open space between the lower and upper halves of the rotor head enclosure. Each half also forms a turbine pressure chamber. This new approach eliminates the conventional mechanical transmission all together, including the free wheel construction (needed for autorotation), as the turbines can spin freely by design. Another remarkable feature is the use of incredibly stiff carbon epoxy blades that allow for a very short distance between the two contra-rotating rotor systems. The revolutionary design of the Sherpa is also seen in the way it looks. The compressor is placed at the rear end of the egg/bullet-shaped fuselage, while the enclosed rotorhead further enhances its futuristic appearance. At the time of writing (2014), there is only a true size mock-up and a 1:5 scale model used to demonstrate the technology in existence. Sagita is aiming for a market introduction by the end of 2015.
|