Failure analysis of LH top root fitting of an aircraft

Evidences suggest that the LH top root fitting of the aircraft has failed by stress corrosion cracking (SCC). Laboratory study showed that SCC was promoted due to poor machining at the fillet region of the component. The stress concentrators and the residual stresses resulting from this poor machining were responsible for the SCC. The situation was further aggravated due to destruction of the surface protective layer at some point of time in the service life of the component. The material of construction was found to conform to specification in terms of composition, microstructure and hardness. No metallurgical abnormalities were found responsible for the failure. A detailed analysis of the failure is presented in this report