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Old 19th October 2007 | 19:22
  #36 (permalink)  
Graviman
 
Joined: Nov 2004
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From: Cambridgeshire, UK
CGWRA, dont forget angle of attack is caused by Relative Air Flow. Even though rotors are at positive pitch, tilting the disk forwards presents a downflow though the rotor, hence negative AOA.

theKite, we are talking gyroscopic nutation here - where movement lags 90 degrees azimuth behind force input. Basically the teetering rotor is always trying to flap back against airspeed, with cyclic input overcoming flapback. The coning means front portion of rotor disk causes a force which would produce starboard roll. By vectoring the forward cyclic position 18 degrees to port, this starboard roll can be revectored to foreward pitch. It only works ideally for coning at 1g, and i won't confuse you with inflow roll which is very similar.

The dynamics of "wee-wa" are a little harder to understand. The rotor always wants to pitch or roll at a constant rate, dependant on cyclic position (teetering delays the fuselage response a couple of seconds though). Once the rotor has established a pitch or roll rate, the aerodynamics act in a similar manner to coning. Thus at a forewards pitch rate the rotor also has little starboard roll rate. Again you revector the foreward cyclic to port roll and it all comes true.

Apologies for not taking much rocket out of the science, but it is a complex problem. I recommend getting a gyroscope from these guys to convince yourself about the 90 degree lag between force input and pitch or roll rate.

Last edited by Graviman; 19th October 2007 at 19:34.
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