FLUG REVUE Special: Helicopter trends 98

OPTIMIZED BLADE DESIGN

For the next helicopter generation, Eurocopter is working on an Advanced Technology Rotor (ATR) with better aerodynamics, simpler blade attachments, and new materials. Beginning in 1998, two flying test-beds are to verify the design's theoretical advantages: A BK 117 will be fitted with the new blades while an EC 135 will be tested with a new bearingless five-blade rotor.

Eurocopter's and DLR's aerodynamical calculations lead to a new blade design which is characterized by a negative trapezoid outline, as well as, modern Onera profile sections of the OA3 and OA4 series, along with an optimized twist. According to Gerald Kunze-Fechner, head of the rotor design division at Eurocopter Germany, this design allows a performance increase of six to ten percent (depending on flight conditions) with the same power setting. The effect of the design can of course also be used to reduce the fuel consumption by using less powerful engines. Four different blade tip designs (see drawings) will be evaluated in flight to check their noise reduction effect in real world conditions.

To improve the comfort, Eurocopter switches from a four to a five-blade rotor design which generally creates less vibrations. Furthermore, the fictive flapping hinge distance will be reduced, which will reportedly be achieved by a new blade attachment with height displaced levers. This allows the attachment of neighboring blades with one pin to the rotor head, which is expected to lead to a weight reduction of 15 percent.

The use of a new fibre/matrix system with R-glass for the spar and cost-efficient 6K carbonfibre for the blade planking are supposed to offer shorter production times and curing cycles, as well as, better material characteristics. First tests of small specimens have already confirmed this expectation.

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Last updated January 15, 1998