Pressure cycles -- Jet aircraft

Is there a life limit on jet aircraft airframes? I know that pressurising and depressurising can eventually result in metal fatigue, and I assume that there is a statutory limit on the number of cycles an airframe can undergo before it can no longer carry passengers for hire.

Is that correct? Is there a statutory limit for each type? Or is it up to the manufacturer?

Many airliners retired from U.S. service go to Third World carriers and/or are put into cargo service. You don’t hear about them breaking up in flight very often. B-52s are famously half a century old and are still used. (I often wonder how close they are to the Ship of Theseus.) Just how long can an old jet airliner fly? Suppose I was a bazillionaire and bought a 727. How long would it last?

You might be able to do this as a mere multi-millionaire: here’s one for $700k. And it has lasted for 47 years and 35,000 hours (that’s four continuous years in the air).

I’m unaware of life limits, and I believe some 747s have flown over 100,000 hours. But note that this 727 has 33,000 cycles. This might mean it’s becoming prone to fuselage cracks which can be … unpleasant. (c.f. Aloha Airlines flight 243).

The life limits (if any) are determined during certification. Some have pressure cycle limits, some have flight hour limits, some have calendar year limits, some have landing limits, and some have no limits. I think it may have more to do with the FAA’s confidence in the manufacturer than anything, but that’s my own opinion.

Also, I’d be careful getting into a $700k B727. I can guarantee that the engines are run out: it’ll cost you at LEAST $3-4 million for those alone. I’d wager you’ll be $6 million into it by the time you’re ready to fly, then your annual fixed costs will be somewhere in the $2-3 million range. Variable maintenance costs are all over the board, but another $500k/yr is probably in the ballpark. THEN you have to put fuel in the thing, and my guess would be 800 gal/hr at $5/gallon.

If you’re a mere millionaire, you won’t be for long. As the saying goes, the only way to end up with a small fortune in aviation is to start with a large fortune!

I’ve worked on aircraft that had hour limits and landing limits. Even these could be SLEP’ed (Service Life Extension Program) by fixing or replacing various components such as wings.

The number of pressure cycles was certainly a worry in the old de Havilland DH 106 Comet. A number of them crashed due to the fuselage blowing apart especially around the cabin windows. The windows were square which caused stress points at the corners in the fuselage.

I don’t know about absolute, can-no-longer-be-flown limits. But I do know that large aircraft (or the sort you’re talking about) have to undergo thorough inspection of the skin and airframe after a certain number of flight hours (thinks it’s about once every year or two for most of an airline’s fleet*.

iirc, this inspection includes microscopic and/or e-ray examination of at least the most stressed parts (usually where the different assemblies (e.g. wing, tail, fuselage sections) join together. These inspections can supposedly detect fractures and other failure points long before they’ll lead to actual failure.

  • I’m not sure what the schedule is for the little <50 passenger puddle jumpers.

As best I know there’s not a regulation saying X cycles is OK but X+1 is verboten. FAR Part 25 covers commercial aircraft certification and requires the manufacturer to determine a service life and an inspection regime to monitor each airframe as it ages in use.

As aircraft get to higher cycle counts, the inspections get deeper and more frequent and as such they uncover stuff that needs fixing. Which repair cost & downtime cost eventually kills the economic lifetime of the aircraft. Nowadays issue like passenger appeal or fuel burn usually put a jet out to pasture first, but the structural lifetime fuse is lit when the manufacturer first delivers the shiny new jet…

One of the reasons FedEx & UPS still use 727s is they fly them so little per day that they can pick one up that’s run-out from the POV of a passenger airline and then get, say, 5 years use out of what the passenger carrier would have used up in just one year. Their much higher revenue margins offset the higher fuel burn. Nowadays we’re seeing even them run out of 727s and they’re picking up old 757s under the same economic logic.

The last aircraft I operated was on it’s 26,342nd cycle that day. I rode on a different type yesterday which was on it’s 33,793rd cycle. Those are middle-aged jets.

For what its worth, Flight 243 had nearly 90,000 cycles on it when it failed, and those were harder than usual due to the salty, humid air.