1. Comet Aircraft Fatigue Failure Group 6

2. Background…. Designed by De Havilland -the first turbojet powered airliner -competition between USA (Boeing) and Britain to produce the most successful commercial aircraft 27 th 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

3. 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

4. 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

5. 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

6. More accidents… 1954 Naples: disappeared, remains found in sea.. -after expensive testing the cause of both these 1954 accidents was found to be… FATIGUE

7. 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

8. 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!

9. 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…..

10. 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

11. Thanking You!!!