The dream that never happened: the Comet aircraft

Commercial jet travel commenced when British Overseas Airways Corporation introduced the Comet Jet in 1952.  Great Britain was first with jet powered aircraft for passenger use. Great Britain had been a leader in jet research going back as far as 1791 when John Barber was granted a patent on a stationary turbine.

BOAC_ComentBritain’s hope for air superiority rode on the success or failure of the Comet. BOAC placed its order for the plane in the late 1940’s, while it was in development.  Indeed, the de Haviland company was THE leader in jet development around the globe. No American company was even close to a production jet passenger plane.

When the plane entered service in 1952, it was the most advance aircraft in use.  The manufacturer put the craft through all kinds of testing, including stress tests. Since the skin was made of an extremely thin and lightweight aluminum, the craft was subjected a battery of stress testing and was thoroughly inspected before each flight.

Technically, the planes should be able to handle thousands of liftoffs and landings without any signs of metal fatigue. Unfortunately, they had a flaw-a manufacturing flaw-that would culminate in catastrophic decompression in about three thousand flights. Two crashes, just weeks a part, in 1954 led to the grounding of all Comet aircraft.  Two investigations were launched, at different times and it was the second investigation (launched after the second crash that year) that actually brought about the discovery of the fatal flaw.

Because it was the 1950’s, and air travel in general was still fairly new, there were few investigative methods or technologies available for determining the cause of a crash. The British investigators had to formulate these methods as they went along. The investigation was slow and hampered by the fact that the craft had gone down in water.  In fact, both craft had gone down in water, with one in rather shallow waters while the other was in far deeper water and not retrievable.

Metal fatigue was suspected, mainly due to the condition of the bodies that were recovered from both crashes.  The bodies revealed skull damage and ruptured lungs. There were scores of broken bones that happened when the bodies hit the water, but the lung and skull damage preceded the actual crash.  Small scale tests were done and show that dummies would sustain the same damage during sudden decompression. But what caused it?

To prove out the theory, an actual Comet was used. A water tank was built up and the Comet placed in the tank.  Both the plan and tank were filled with water, with the plane getting more water to simulate the pressure it would sustain at 11,000 km.  The test was repeated, around the clock for nearly a month.  The last test caused the decompression.  The fracture was traced to rivet holes around the window.

Problem was that none of the retrieved metal from that first crash show such fatigue.  Luckily, though, a portion of the roof was retrieved shortly after the test and it did, in fact, show such fatigue.

Minute cracks, caused when the rivets were PUNCHED into the metal, grew over time as the plane was pressurized and depressurized.

While the cause was finally found and corrected, the Comet was grounded, commercially, until 1958. During the intervening years, Boeing introduced its jet airliner and many of the world’s major airlines purchased them, leaving de Haviland, and Britain, behind.  Great Britain’s hope for air dominance faded.

In all, there were four models of the Comet.  The last Comet was retired in 1998.  The Comet’s design, however, still looks fairly modern. It’s clean lines and overall shape still say ‘I’m the future’.I love the way this craft looks and it reminds me of the hope that many held for the future.

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