- Jan 2, 2009
- Centre FRANCE
- I piloted gliders C800, Bijave, C 310, airplanes Piper J3 , PA 28, Jodel D117, DR 220, Cessna 150, C
- Total Flight Time
- About 500 h (FW + ultra light)
I agree with you on this point.What I said is, that with a rotor the reaction always follows the applied force or moment by a phase lag of 90° since the rotor is a second order system in resonance, so maximum flapping occurs over the nose since the maximum moment from cm is applied at the point of maximum flow velocity, i.e. at psi=90°, where psi is the angular blade position and psi=0 is over the tail of the aircraft.
This is where our opinions differ, Juergen,As for the position of maximum angle of torsion, if you refer to the case of the external weight (not the case of maximum moment due to cm) then I’ll stick by my guns. The maximum torsion of the blade due to the external weight takes place at the point of maximum acceleration due to rotor flapping, which is over the nose of the aircraft.
During a revolution, the blades must cyclically correct their angle of attack to compensate for their airspeed variations during forward flight, and thus prevent roll. This is usually achieved automatically by the longitudinal flapping.
Despite of this flapping, the axis of the shaft having to continue to include the V formed by the blades (coning), must impose angular oscillations to him and overcome its inertia.
This is the 2/rev vibration explained already many times by Chuck Beaty, whose torque is maximum at 3 o'clock - 9 o'clock.
The angular inertia due to the external nose weight is only added to that of the blades V.
This cyclic torque can produce a proportional torsion of the blades, forcing to push the stick further forward to keep the level (By definition, a longitudinal flapping increased)