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Old 26th April 2011 | 10:01
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delta3
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Joined: Apr 2004
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From: Belgium
Time lags cyclic control

Levi

Two main groups:

1. The rotor reaction time, depends on many parameters, but is in general very fast, typical 1 to 2 revolutions to execute the cyclic command. On a R44 that is approx 1/5th of a second.

2. The body is a different ball park. In general it is much slower.

2.1 First there is the rotor stiffness as per Crab. Theetering has stiffness 0, multiblades (even with free flapping hindges) are more stiff. That means the rotor can transmit cyclic torques at the rotor head. The stiffer the rotor the faster the response of the hull.

2.2 Inertial forces combined with aerodynamic forces (fins) and gravity explain the rest. They are the slowest (multi second, not hours). They are also the only one's for theetering rotors. The precise dynamic parameters are known by the constructor because they explain the flight behaviour (dutch roll etc). Given some more time I could get some precise time constants out of my R44 model, for for instance lateral and forward cyclic.

Hope that helps, d3
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