Failure Analysis of the Restraining System of the Directional Rudder of an MD80 Aircraft
The directional rudder travel of an aircraft must be restricted as the speed in flight increases, this in order to decrease its sensitivity, thus avoiding maneuverability problems or overloads that could result in a break in the vertical stabilizer and cause an accident. aerial. The aircraft MD 80 have a system of restriction of the route of the directional rudder, whose main component, the hook, is the piece in charge of stopping the movement as it is introduced in the piston rod of the hydraulic cylinder that governs the movement of the rudder. In this work, the causes of the hook fractured that left the directional mechanism out of service is analyzed. In order to carry out the work, the manufacturing material of the piece was first characterized, doing the analysis of its microstructure and alloying elements, it was obtained that it has the typical characteristics of an AISI 4340 steel. Subsequently, the loads acting on the piece in service condition and the initiation of the crack route were determined. Then, the fatigue study was carried out through simulations using the finite element method. The results were that the piece failed due fatigue due to a superficial defect.
Luis Rodríguez-Tembleque, Jaime Domínguez and Ferri M.H. Aliabadi
J. Coronado et al., "Failure Analysis of the Restraining System of the Directional Rudder of an MD80 Aircraft", Key Engineering Materials, Vol. 774, pp. 77-83, 2018