The de Haviland Comet?

Question

Can anyone tell me a little about the Comet's inception and some of its tragedies; what faults occurred, etc.

Thanks.

Answer 1

Bits used to fall off them when they were up in the sky.

Answer 2

There were a combination of reasons.  The use of very thin aluminum for skin as weight saving measure, the use of bonding instead of rivets, and finally the infamous square windows.

The problem was that in the 1940s when the plane was designed, very little was known about the effects of cyclic stress leading to metal fatigue and that these stresses tend to concentrate on areas where there are sharp corners or drastic changes in material thickness.

As a result, while the Comet fuselage could withstand over twice the pressure differential it was designed for, it was still too weak to withstand the stresses of repeated pressurization cycles over a period of time.

The Comet disasters changed the way aircraft are built and tested.  Now every pressurized aircraft must be fatigue tested as well as have an ultimate strength test.

Edit: Guy, you are right.  The windows were riveted and it was a contributing factor.  They were designed to be bonded like the fuselage but instead were 'punch riveted' which created further weaknesses in the design.  I guess you learn something new every day, I thought it was the bonding that was part of the problem.

Answer 3

It had squarish windows. Hairline cracks appeared around the rivets due to uneven stress on the structure & spread through the fusalarge causing failure. They changed the design to round windows which fixed the problem. But the damage had already been done & the comet is no more. They immersed the commet in a massive water take minus the wings & pressuried it to see where it failed. I think the Nimrod that the RAF use is basically a comet.

Excuse my spelling I have had a few & can not find my dict....

Calnickel. Were the windows bonded as well. I thought they had rivits in the windows. I do not know to much about the comet. If I got that bit wrong I apologise.

Answer 4

The first jet passenger liner The design originated in the late 1940's A superb British innovation No real ancestors designwise Unfortunately the windows were the wrong shape and caused many catastrophic decompressions and crashes The most infamous were in India and in the Mediterranean Modifications came later and new Comets were still coming out in 1960 but the reputation from the earlier failures were not forgotten and by that time the Boeing 707 had come along.In spite of this Comet is still in military service reincarnated as Nimrod

Answer 5

The Comet, hailed as the first viable jet powered passenger liner, suffered from some basic structural defects. The primary one being the design of the windows. Any aircraft that is pressurized  must allow the fuselage structure to "flex"; expand and contract as the plane pressurizes and depressurizes. The design of the Comet's passenger windows allowed cracks to develop in the fuselage structure after a number of flights.

The first few Comets suffered catastrophic structural failure in flight causing the breakup of the aircraft with loss of all aboard. Subsequent water pressure tank testing revealed this design flaw and the remaining Comets were grounded.

Answer 6

I am not 100% sure but I think the present Nimrod surveilance aircraft is a developement based on the airframe of the original de Haviland Comet 4.

Answer 7

The aviation industry learned a lot about metal fatigue and the effects of pressurisation from the Comet, unfortunately the hard way for the passengers & crew as already described. These were the principal disasters:

May 2, 1953: G-ALYV disintegrated in a thunderstorm at

10000 ft during its initial climb on a flight from Calcutta

to Delhi

January 10, 1954: G-ALYP crashed from at 27000 ft in good

weather on a Rome to London flight

April 8, 1954: G-ALYY disappeared on a flight from Rome to

Cairo. All Comet aircraft were grounded until they found the problem.

The Nimrod is not a retread Comet, but some of the basic design principles are still used in it.

Answer 8

There was a design flaw in that the cyclical pressurisation and de-pressurisation caused catastrophic failure of the airframe during flight.

These failures and subsequent innovative tests using water tanks were shared with Boeing who were designing the 707 at the time and they adjusted their design.

Unfortunately, despite fixing the design, the Comet IV (its final incarnation) was not a commercial success.  It was very comfortable and revolutionary.  The design is so graceful with the engines embedded in nacelles in the wing stubs.

It's spiritual or design successor was the VC-10 which is still in use by the RAF as fuel-tankers (though they are seriously showing their age).

It is such a shame the British were able to design gorgeous looking aircraft - Comet, VC-10, Concorde though none of them became commercial successes.

Answer 9

Calnickel's explanation is spot on. The various incidents that plagued the Comet did in fact lead to a greater understanding of fatigue and failure mechanisms in aviation. Unfortunately this is the nature of aviation advancement - much of it leads from what we learn from investigating and analysing aircraft disasters.

The Nimrod MRA4 ( a martime reconnaissance & attack aircraft) , which is due to enter RAF service in the next couple of years can be considered as a "grand daddy" to the Comet - however the MRA4 is essentially a brand new aeroplane, sharing only one component common to the Nimrods of old.