ground resonance


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ground resonance

A resonance that manifests itself as a violent rocking of the helicopter when it is on the ground. This phenomenon is most evident when the helicopter is on hard surfaces that do not absorb vibration. It is caused by the resonance between the skid and the rotor system. It is most likely if the helicopter has a fully articulated rotor system that experiences a hard impact, such as the helicopter hitting the ground with a single skid while landing. The resonance can either build up slowly, with the oscillations gradually increasing in amplitude, or extremely rapidly. If uncorrected, the helicopter can roll over and break up. To prevent this critical situation, either the engine should be switched off if the rotor RPM is low or the helicopter should takeoff by applying more power.
References in periodicals archive ?
They cover notions of instability, rotor/structure coupling: examples of ground resonance and air resonance, torsional system: instability of closed-loop systems, self-sustaining instability for rotating shafts, and fluid-structure interaction.
Flights will likely be limited to the traffic pattern, he adds, after initial ground resonance and hover testing flights are completed.
EMIStream simulation is based on a SPICE model and provides accurate simulation of power and ground resonance noise in a relatively short calculation rime (around a few minutes per plane).
Westland is now part of a growing number of helicopter companies that use ADAMS software to understand dynamic behavior, stability, and loads in helicopter design, as well as simulate and study landing gear drop, taxiing, ground resonance effects, command lines, rotor and swash plates, and tie- downs.
Simon Newman addresses the unique considerations applicable to rotor UAVs and MAVs, and coverage of blade dynamics is expanded to include both flapping, lagging and ground resonance.