T.T. Lam - Post-graduate Student, Moscow Institute of Physics and Technology (State University). E-mail: tangthanhlam@gmail.com

This paper presents a study of three dimensional minimum-fuel turn and minimum-time turn for a light aircraft. Here fuel-optimal and time-optimal control problems are considered with boundary conditions and full constraints on the state, control variables. The optimal trajectory and controls are computed to bring the aircraft from initial position, altitude, speed, flight path angle, heading angle to final correspondent conditions with 180° turn. The rate limits of control variables are applied to engine thrust, bank angle and angle of attack. In order to find a numerical solution to the optimization problem, Gauss pseudospectral method is applied. The optimal control problem is transcribed to a nonlinear programming via a Gauss pseudospectral method and is solved using MATLAB and its Toolboxes. The numerical results are given for an agricultural aircraft (mass 550 kg) on a turn maneuver while performing spraying crops.