Active Helicopter Rotors

During the nominal rotation of a rotor, the rotor blades move out of the rotor plane (flapping) and in the rotor plane (lead-lag-motion). The lead-lag motion suffers from low damping which can result in resonance phenomena such as ground- and Air-resonance. In order to prevent such resonances, a control concept was developed that makes use of TEFs such that the damping of the lead-lag-motion is increased. This control concept was implemented on a full-scale EC145 and its functionality was demonstrated for the first time (worldwide) through flight tests.

A part of helicopter vibration is originated by blade dissimilarities. These dissimilarities cause the rotor blades to travel on different paths leading to static and dynamic imbalances, which in term lead to vibratory loads in the airframe. To minimize these vibrations a control concept was developed, which a continuous adaptation of the rotor tracks over the whole flight regime through control. It was demonstrated the first time (worldwide) with flight tests on a full-scale EC145.

Individual blade control has shown its potential for various control tasks like helicopter vibration reduction and lead-lag damping enhancement, on an EC145 (four rotor blades, 3,5t), the rotor of which was equipped with active TEFs. Ongoing work focuses on the scaling of this technology to other helicopter configurations with respect to the IBC actuation system, blade number or the size of the rotorcraft.