Actually, the Comet fuselage failure was somewhat more complex than just bad design. First, there was a paperwork error that mislocated a rivet in the windowframe by about 1/4" toward the outside, virtually certain to cause a fatigue failure. This was NOT a design error, it was an error introduced during drafting.
Second, the particular window frame affected just happened to be at a very high stress point as it was directly below the corner of the fiberglass panel in the roof for the internal radio antenna system, so that a window failure resulted not in a blow out window but a massive failure of the entire row of windows, resulting in the complete disintegration of the airframe. Progressive failure of a fuselage like the original Comet design has been prevented in all latter aircraft by a "rip reistant" design pioneered by the Comet design team. You should note that the Comet in it's original form had four 5000 lb static thrust de Havilland Ghost engines, grossly underpowered even in the "featherweight" structure -- the functional equivlanet of one engine on a Boeing 707-200. Later models had about twice the engine power and better structure. The Comet was also pressurized to 9.5 psi, about a third higher than current aircraft, and flew at 40,000 plus ft altitude fully loaded. A contemporary DC-6 could stagger all the way up to 25,000 ft, was pressurized to 4.5 psi, and was almost 200 mph slower. The Comet was already slated for complete replacement due to structural inadequacy before the fuselage failures -- there was at least one, probably two, crashes of the original design traced to wing fatigue greatly acclerated by turbulence (and severe turbulence shortly before the failure was a factor in both fuselage failures). De Havilland was in the process of reworking the whole design inside the company to greatly increase capacity (only 40 passengers in the original design) and to carry much more fuel and heavier engines. All this was done by hand with slide rules -- massive failures in cutting edge aeronauitical designs were more or less the rule in those days of puny engines and fairly primitive understanding of modern aerodynamics. So far as I know, no Comet 4 every suffered a severe structural failure, and corrosion problems are NOT a design defect so much as a maintenance or ignorance problem. Ditto for the tail icing crashes that brought down some Viscounts (and was a problem on Brittanias, too, I think) -- to be a design defect the problem has to be known and understood during the design phase, and no aluminum plane has lasted long enough prior to WWII to develop fatigue problems -- they were all destroyed by unrealted crashes or fires or obsoleted before the accumulated enough hours of use to show fatigue. Bad drawings are a technical deffect, but hardly a design problem. I don't know what would have happened if the rivet had been correctly placed, but having where it was reduced the fatigue resistance upwards of 90 %, and the "test" airframe had a minor failure there before the side blew out in testing. The Nimrod the RAF used up until very recently (if it isn't still in use for antisubmarine work) was a Comet 4, not a refitted Comet I or II -- the only Comet I or II airframes built were for commerical customers, and there weren't more than 25 assembled before the fuselage failiures became known. All were scrapped post-haste. The Comet 4 entered service in 1956. After all, anybody who ever flew a Curtis Commando will tell you about design defects -- electrical, hydraulic, and pnematic lines all going through the same hole in the frame where the control stick could rub on them is one example....almost gaurenteed a massive fire someday. The Avro Jetliner was a wonderful plane, killed by the American aircraft manufacturers via the Canadian goverment. It had much the same operational characteristics as a DC-9/737 minus the short feild capability, and if the Rolls Conway had been available, would have eaten Boeing's lunch in short haul jet transport. Brilliant design, but due to political shenanigans was blowtorched and landfilled, blueprints burned. Ship one rolled off the line in 1949, almost a decade before the US builders popped out a jet passenger plane. Ditto for the Arrow in 1961. The DC-3 was known as a very reliable aircraft in WWII, but it had been carrying passengers since 1934 and all the "infant mortality" had been worked out -- like a cover over the control column pivot so a pilot's headphones couldn't slide down and jam the column in full down or up position..... External gust locks for the fabric tail crashed any number of DC-3, etc etc. Peter
