Kinematics of Nose Landing Gear for RLGS Mechanism of MALE UAV

Electrical linear actuators reduce the weight of landing gear retraction / extension mechanism which helps in keeping the gross takeoff weight of aircraft weight low. Reduction in weight of the aircraft has manifold advantages in which noticeable are increased endurance, range, climb performance, acceleration performance and fuel efficiency. Use an electrical linear actuator in landing gear system is a simplification in the kinematics of landing gear retraction / extension sequence. In this research, a retraction / extension mechanism for nose landing gear (NLG) of a MALE UAV has been designed and tested according to FAR CFR 25.729. The design process of a Retractable Landing Gear System Mechanism (RLGS) started with selection of pivot point on NLG and axis for the rotation in free space available which resulted in least power requirement. Pivot point was selected such that no part of gear posed hindrance to other part of an aircraft. Next, the path of rotation about pivoting axis and position kinematics were calculated using vector loop closure equation. Essential parameters regarding retraction / extension sequence were calculated from trigonometry. Forces and power required for complete retraction / extraction sequence were calculated. During the research, it was found that retraction force on NLG depended upon the aerodynamic drag, inertial loads and gravitational force. In this research analysis of these forces is presented with much detail. Effect of velocity variation of linear actuator on the retraction force is commented upon. Computational analysis is carried out using multibody dynamics MSC ADAMS® software. The research concluded with experimental validation of a planner triangular retraction mechanism of NLG actuated by electrical linear actuator.