Design Modification of Mechanical Flight Control Circuits of an Intermediate Aerobatic Trainer Aircraft for Improved Efficiency

Abstract

In a typical Intermediate Aerobatic Trainer Aircraft (IATA) the primary control surfaces viz, Ailerons, Elevator and Rudder are operated mechanically and thus called Mechanical Flight Control System (MFCS) consisting of elements such as push-pull rods, levers, torque tubes etc. Design considerations for such MFCS include strength, stiffness, ergonomics, low circuit friction, kinematic feasibility etc. During the developmental flight trials, in one of the prototype aircraft, it was found that full control surface movement was not achieved under maximum aerodynamic load. This led to the reduction in efficiency of the system. Based on the analytical calculations and Finite Elemental (FE) simulations, it was found that considerable elastic deformation of mechanical elements as well as support structure had lowered the efficiency which was also validated experimentally. Although, aircraft handling qualities were found to be satisfactory during the normal flight testing, it was desirable to improve the efficiency of the MFCS. This paper broadly outlines the methodologies adopted to improve the efficiency of the existing control circuits considering aero-elasticity and structural design aspects