To: Dave Jackson
>"My point is that when you make everything unearthly rigid, you have turned the helicopter into a gyroscope. "<
Only the rotor is a gyroscope; in the horizontal plane
The whole helicopter is *starting* to become a gyroscope in the vertical-longitudinal plane, but, this will only last until the desired nose-down pitch is achieved. Then all precessions stop.
Response:
Why do you continually limit yourself to rigid rotors having gyroscopic tendencies and not consider that other rotors exhibit the same characteristics. The only difference is the level of interlock between the blades and the rotorhead, which effects the response to control input.
>" You apply the upwards force to the tail, a moment is created, angular momenta are summed, and the helicopter rolls a very small amount to the left. "<
Response:
In the Ditching thread, I indicated that when a helicopter is on a pitching and rolling deck the perturbing force on the spinning rotor in the form of ships motion will result in the rotor system moving in response to that input. This response was in the form of gyroscopic precession. Nick Lappos who said it never happens crucified me. Now a theory is being postulated that if on a rigid rotor helicopter the fuselage were moved upward by the tail boom the rotor system would precess. I totally agree but I also believe the same thing would happen on any other helicopter because I experienced this phenomenon on the back end of an icebreaker. Both types of heads were represented. One was a Bell and the other was a Sikorsky.
“The very small roll to the left can be also explained aerodynamically and the change in pitch is exactly what we commanded.
Response:
How can you explain this phenomenon by introducing aerodynamics as the partial cause of the rotor movement? There was no introduction of pitch change and the motivating (perturbing) force was someone pushing up on the tail boom.
[ 25 November 2001: Message edited by: Lu Zuckerman ]