Abstract
Two major assumptions adopted in the current helicopter motion analysis are examined. It is shown numerically that to neglect the laterallongitudinal coupling motion may lead to about 20% error in the control response at lower fre- quencies, and that the quasi-static rotor assumption (or HOHENEMSER's assumption) can also produce about 20% error in the pitch damping at the frequency region of the short period mode. The coupling effect is remarkable for blades with large Lock number and is sensitive to the inflow distribution, while the effect of rotor dynamics is predominant for rotors with small Lock number or small rotational speed.
