Failure Analysis and Measures on Cracking of Rear Beam of Horizontal Stabilizer of Aircraft

The intermediate section of the rear beam of an aircraft horizontal stabilizer was found to have cracks and corrosion after service for a while. The cause for the cracking was analyzed by macro and micro observation, metallographic examination, hardness testing, energy spectrum analysis as well as analyzing product design and manufacturing processes. The results show that the cracking mode is stress corrosion cracking. Sulfide and chloride corrosion products were found at the cracking fracture surface. The surface protection layer had been damaged during manufacturing process. The co-effect of residual stress and working stress resulted in the cracking of the LD5 aluminum alloy during service in the Cl-rich environment. Taking various factors of cracks and corrosion into consideration, several practical and effective measures were put forward to prevent this kind of failure and prolong the life of the aircraft body.