Method of and Device for Actively Damping Vertical Oscillations in a Helicopter Carrying a Suspended External Payload

A method of damping vertical oscillations in a helicopter having a rotor drive-unit and an airframe and which carries an external payload suspended via a lifting gear from a load attachment point on the airframe of the helicopter, the method comprising the steps of:

• arranging oscillation sensors on the helicopter;
• providing an actively operated linear actuator operative between the load attachment point and the lifting gear;
• sensing, with the oscillation sensors arranged on the helicopter, excitations at least of a first mode of the vertical oscillations, in which first mode the external load
• and the rotor drive-unit oscillate together relative to the load attachment point, and of a second mode of the vertical oscillations, in which the second mode the load
• attachment point oscillates relative to the external load and the rotor drive-unit, with regard to both phase and amplitude of the excitations;
• and
• applying, between the load attachment point and the lifting gear with the actively operated linear actuator, forces opposed to the vertical oscillations as a function of the phase and of the amplitude of the sensed excitations.