Trim Analysis of Helicopter Rotor in Forward Flight

Rotor trim is an important prerequisite for conducting an accurate aerodynamic computation of helicopter rotor. In order to accurately obtain the rotor control settings such as collective pitch and cyclic pitch, trim analysis of helicopter rotor in forward flight based on CFD method is carried out. Firstly, a rotor trimming method for forward flight and CFD numerical method are introduced. Then, the moving-embedded grid method is applied to perform trim calculation on the flowfield of AH-1G rotor under forward flight test condition. Finally, the CFD calculation of rotor control settings are compared with flight test data. The comparison results suggest that the rotor trimming and CFD numerical methods are reasonable and feasible for the numerical simulation on unsteady flowfield of a trimmed rotor in forward flight. Compared with flight test data, the calculated collective pitch of trimmed AH-G rotor is about 0.19 degrees smaller with an error of 3.2%. The calculated rotor control settings have a certain degree of accuracy, which can meet the engineering application needs on evaluation of trimmed helicopter rotor control settings and lay the foundation for further accurate numerical simulation research of rotor aerodynamic characteristics.