[pjc50]

They were an amazing example of a legacy system being maintained far beyond any reasonable expectation of life at gradually increasing cost, to a great extent because nobody could agree on a replacement and the one-off cost of a replacement was always a bit more than the endless "maintenance" and "refurbishment".

If I remember rightly the refurbishment project hit the problem that, because the original planes were hand-built to 1950s tolerances, building new parts off the original plans simply wouldn't fit. The only viable approach was measure the specific plane you wanted to fit, and build a custom part for it.

Eventually one simply caught fire in the air: https://www.telegraph.co.uk/news/1528109/Fire-was-reported-o...

The destruction of the airframes was controversial: https://www.bbc.co.uk/news/uk-england-12292390 but I see it as a symbolic driving of a stake through the heart of a project that should have been honorably retired a couple of decades previously but instead took on a vampiric, undead, and ultimately fatal life.

[KineticLensman]

> Eventually one simply caught fire in the air

Full details in the Haddon Cave report [0], the official investigation into the crash of Nimrod MR2 aircraft XV230 in Afghanistan in 2006. The 'simply' here (as in 'simply' caught fire) was in fact a catalogue of known problems and missed opportunities. The Nimrod variant involved was originally intended to perform long-duration maritime surveillance and was designed to allow the crew to intentionally switch off one of the engines when the plane arrived on station (to save fuel while loitering for hours). To restart the engine there was a pipe routed through the fuselage that carried hot gases from the running engine to kick start the cold one.

A separate modification of the complicated tanks and plumbing that supported in-air refuelling led to a (leaky) fuel pipe that was routed right past the (very hot) engine cross-coupling pipe. Very minor leaks somewhere in the system were routine.

In this case there was a fuel leak near the engine cross-coupling pipe. The unfortunate crew of 14 had six minutes from initial fire warning to the eventual and unavoidable explosion that killed them all.

[0] https://www.gov.uk/government/publications/the-nimrod-review

[kevin_thibedeau]

The B-52 program is slated to have a 95 year operational time span. Partly as an experiment in maintaining old aircraft.

[cstross]

Yes, but Boeing built 744 of the things, and only 78 (or fewer) are still in USAF service (I believe NASA has one …). So the ones being upgraded are from a late production batch (the B-52H) and presumably by that point Boeing had standardized things properly.

Comet production ran to 114 aircraft in four major versions, of significantly different size and engine configuration (they started with a 36 seater, and ended up with 119 passengers in a charter-variant of the Comet 4C). No individual model of Comet got anywhere close to a triple-digit production run.

Oh, and 26 hull loss accidents!

[billfruit]

Sometimes amazed at how old some of the aircraft still in service are with many airforces/airlines . Just about 3 weeks ago an Iranian airline crashed a 707 in active service.