Fatigue failure of the de Havilland comet I

Abstract The de Havilland Comet I entered service in 1952, and became the first commercial airliner to be powered by jet engines. It was introduced as the flagship aircraft on the routes of the British Overseas Airways Corporation, and was hailed as a triumph of British engineering. However there were a number of accidents involving this aircraft, culminating, in 1954, in the loss of two aircraft in similar circumstances. These were Comet G-ALYP near Elba, and Comet G-ALYY near Naples. A Court of Inquiry was convened, and the task of discovering the cause of these accidents was given to the Royal Aircraft Establishment at Farnborough. The investigation explored a number of avenues, and finally gave structural failure of the pressure cabin brought about by fatigue as the cause of the accidents. The use of fracture mechanics methods not used in 1954 has enabled the analysis of these fatigue cracks to be made, and the initial defect size has been estimated to be approximately 100 μm in the case of G-ALYP. This is not incompatible with the manufacturing techniques of the time, and information regarding cracks in the cabin identified during manufacture.