Flight Trajectory Optimization to Minimize Ground Noise in Helicopter Landing Approach

Abstract

The purpose of this paper is to optimize helicopter flight trajectories to reduce ground noise in the landing approach using an optimization technique and to conduct flight experiments to confirm the effectiveness of the optimal solutions. The Japan Aerospace Exploration Agency has thus far measured helicopter noise under various flight conditions. This study builds a noise model of the helicopter in which the level of noise generated from a point noise source is a function of the flight path angle and bank angle. Then, we define optimal control problems that minimize the noise levels measured at points on the ground surface using equations of motion of 3 degrees of freedom for three-dimensional flight, and obtain the optimal controls for some flight constraints and wind conditions. The obtained optimal flights avoid the flight path angle that generates a great deal of noise and skirt the measurement points; these optimal flights are different from the conventional flight. Finally, this study verifies the validity of the optimal flight patterns by means of flight experiments with an experimental Japan Aerospace Exploration Agency helicopter. The actual flights following the optimal flights result in noise reduction and prove the effectiveness of the optimization.