Mechanical Flight Control System Research Articles

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

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

Stiffness Calculation and Predetermined Preload Optimal Design of Cable Control System

The stiffness of cable flight control systems is one of the most important design parameter for aviation aircraft, because it can change the characteristic of control stick and influence the maneuverability and stability of the flight control system. Flexible cable control system is the main type of mechanical flight control system, in which movement can only be transmitted by cable in tension, the stiffness of cable control system is affected mainly by predetermined preload(PP), however the excessive PP would increase friction between cable and pulley which leads pilot an unfavorable maneuver. In this paper, the theoretical stiffness calculation of cable control system with the complex cable braided construction has been calculated and discussed, in addition the effects of cable deflection and linkage pulley are taken into account to obtain a precise stiffness calculation, and also the predetermined preload related to friction is studied through numerical example, as well as the numerical results have been compared with the experimental results.