Comet Aircraft Fatigue Failure Group 6 Background…. • Designed by De Havilland -the first turbojet powered airliner -competition between USA (Boeing) and Britain to produce the most successful commercial aircraft • 27th July 1949 – flight of the first prototype • The first passenger flights began in 1952 -From London to Johannesburg -Flight time decreased from 40 to 23 hours All seemed well!!...... • • • • • Smooth engine Fuel Efficient Low Maintenance Costs Little Vibration Pressurised Cabin - Could fly over storms when other aircraft had to fly through them Technical Description… • Length ~ 90 – 100 feet -Very comfy with only 11 rows of seats!! • Thin metal skin (“Redux” panels) with low wings -Lightweight, low drag design • Pressurised Cabins • 4 Ghost 50 turbofan engines in the wings -more complicated wing structure -again, less drag Just when they thought they had it… • 1952 Rome: failed to become airborne Pakistan: ran into bridge, 11+ fatalities -both blamed on pilot, later found to be aircraft • 1953 Calcutta: disintegrated in thunderstorm -design fault → wing design reprofiled -43 fatalities • 1954 Italy: exploded and fell into sea -initially believed fire was the cause, next accident proved otherwise -35 fatalities More accidents… • 1954 Naples: disappeared, remains found in sea.. -after expensive testing the cause of both these 1954 accidents was found to be… FATIGUE Testing….. • Full-scale flight simulation testing began • Large tank was built to hold an aircraft, water was used to imitate cabin pressurisation cycles and wings were jacked to simulate typical flexing Test Results…… • Stress around windows was higher than expected, due to stress concentration caused by square shape • Poor placement of engines in wing design, had negative effect on lift-off potential and was a fire hazard • Many modifications were made.. windows were redesigned to an oval shape and the skin sheeting was thickened, flights started again….. 4 years later! Oh Well…! • The damage done to the Comet Aircraft’s reputation was beyond repair • Boeing had taken the lead with commercial jet manufacturing • Production of the Comet Aircrafts ceased after just another 10 years….. Into the Future…and Beyond!! •Full-scale testing of aircrafts used in future •Much better understanding of fatigue and fatigue testing achieved •Learned the importance of minimizing stress concentrations •New knowledge of materials Thanking You!!!