CALCULATION OF HELICOPTER ROTOR FLAPPING ANGLES AND COMPARISON WITH MEASURED DATA

摘要

Helicopter rotor flapping angles from hover to low-speed forward flight are calculated and compared with the measured data in this paper. The analytical method is based on a second order lift- ing-line/full-span free wake model as well as a fully coupled rotor trim model. It is shown that, in or- der to accurately predict the material flapping angle at low advance ratio, it is necessary to use free wake analysis to account for the highly non-uniform inflow induced by the distorted wake geometry at rotor disc plane.