Carbon with high-strength aluminium hub
The propellers are designed for being driven by multi-pole electric motor, such as the HPD 10 or HPD 13,5 having few torque oscillations. The use of differing drive motors, especially combustion engines, may cause the immediate or gradual destruction of the air screw.
The propeller needs to be accelerated softly during the start-up process until the blades are in working position (outspread), in order to prevent hard strikes to the end stops of the hub. For this purpose fixed programmed acceleration and deceleration ramps of the drive motor are required.
The limit speed is obligatory to be observed. Rotational speed in excess may cause the destruction of air screw or hub, due to the high centrifugal forces. The limit speed of air screw with 1,4m diameter is about 2200 1/min., limit speed of air screw with 1,3m is about 2300 1/min.