PREDICTION OF CONTROL SYSTEM LOADS IN LEVEL FLIGHT AND MANEUVERS

The objective of this work was to reduce the part played by empiricism in the estimation of control loads affecting helicopter mechanical flight control systems, A tool was developed which embraces a suitable level of modeling complexity and which runs efficiently. Performance of the analysis was evaluated by comparing predictions with test data derived from flight and model tests. Curves of predicted variations of push-rod load with respect to time show fair to good correlation with measurements. Peak-to-peak values are faithful to trends as extreme flight conditions are approached in level flight, a 45° angle-of-bank turn, and a symmetric pull-up. Peak-to-peak curves of torsion bending moment for powered models follow trends shown by wind tunnel data with increases in CT/σ. The analysis did not predict very accurately amplitudes or phases of harmonics of push-rod loads and stationary servo loads but trends were fair. The analysis shows ability to reflect the physics of rotor configurations and flight conditions and it advances on an empirical solution.