Fracture and Failure Analysis of the Trainer Aircraft Rudder Pedal Hanger

Abstract

This study analyzes the T-38A Talon twin-jet trainer aircraft rudder pedal hanger damage due to the fracture that has been identified at the clevis surfaces where the tension rises. The hanger has the function of swinging the rudder pedal under irregular tension loads. The fractured hanger material is magnesium AZ91C-T6 cast. The composition of the hanger is 90% Mg, 8.1–9.3% Al, 0.4–1% Zn, 0.3% Si, 0.13% Mn, 0.10% Cu, and 0.01% Ni. The average hardness value of the material was measured as 77 Hardness Rockwell-C (HRC). The oxygen and chloride pollutants had been observed under Field Emission Scanning Electron Microscope (SEM) and EnergyDispersive X-ray Spectroscopy (EDX). The mentioned pollutants were considered as the main factors for decreasing the corrosion strength. The mentioned corrosion augmented the crack propagations from multiple origins of the rudder pedal hanger. The fracture and failure analysis results demonstrate that the corrosion pitting associated the fatigue under the influence of repeated loads. Eventually, after the crack had grown catastrophically, the residual cross-section surface could not endure the repeated load overcoming on it, the clevis of the hanger was completely fractured into two pieces.