Really Interesting Article About Old Airliners

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privateer

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All it takes to keep an airliner in service forever is money. Therein lies the rub.

The DC's are grand, tough birds.

My grandfather worked at AA in contracts when they bought the BAC-111 because they were promised they could be delivered a year before the DC-9. That year came and went with nary a BAC-111 in sight. AA dispatched a team to the UK including my grandfather. He said they were driven for hours (partly through the Queen's forest) to the manufacturing site, whereupon they found rows and and rows of Quonset (sp) huts. Each had workbenches from stem to stern inside, where workers were basically handbuilding all the parts. The AA guys popped a fuse, but they were told there was nothing to be done about it; it was part of Labour's full-employment policy.

Another AA retiree told me that the pilots loved the BAC-111 because it handled like a military jet trainer. He also said mechanics hated it because parts were difficult to install (re: handmade). I've had others tell me the same.
 

Gym_Class_Hero

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Hand made, really? No wonder the thing basically fell off the planet.
 

troj

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I didn't know the return to service rate could be as high as 90%.
Doesn't surprise me -- it's all a matter of what they're willing to replace over time.

Consider this... The US Air Force doesn't have a B-52 that didn't roll off the assembly lines before I was born....over 40 years ago.

Properly maintained, aircraft can last a long time.

-Kevin
 

mach7

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Thats one of the reasons that the INF treaty had Russians watching us slice B-52s in the early '90s. Once the airframe was sliced the aircraft was considered unrepairable.

on thing that I find interesting is that the Airbus aircraft have a definite end of service life. They don't use a thru wing spar to save weight. It is my understanding that because of this the can not exceed this time limit.
 

privateer

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Traditionally commercial transports don't have a service life. They used a different philosophy, first "fail-safe" which instead of a fixed life says that loads can be carried on secondary paths until the primary failure is found during routine inspection (or earlier) and fixed. This has been superseded by "damage tolerance", which uses an inspection program to find detectable faults before failure.

The military typically used a "life limited" approach, which is that nothing major will fail for a given period, say 10,000 hours of flight time. When military aircraft near that limit and require further service, a "service life extension program" may be carried out to extend the life by analysis, inspection or modification or some combination thereof.

Airbus may use a service life; I don't know.

The FAA is nearing rulemaking that essentially will put a life limit on aircraft. The concern is "widespread fatigue damage" that as I understand holds that after so long multiple element/multiple site fatigue damage may exist and have the potential to propogate so fast that practical inspection intervals can't catch them. This is a really controversial issue. The verbage used is "limit of validity" in which the OEM basically says "based on our testing, analysis, and service information we are confident the existing inspection program will remain valid until a certain number of hours/cycles and beyond that...we don't know at the moment". It is not exactly a life-limit but economically it probably will be. The limit is quite large for most aircraft. DC's are tough and the LOV proposed is 60,000 cycles / 150,000 hours for DC10's. I don't think any DC10 at the moment has reached the proposed LOV and later production planes are relatively far from it.
 

troj

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The FAA is nearing rulemaking that essentially will put a life limit on aircraft. The concern is "widespread fatigue damage" that as I understand holds that after so long multiple element/multiple site fatigue damage may exist and have the potential to propogate so fast that practical inspection intervals can't catch them.
If I remember (going back to stuff I've read in the past, and this is hardly an area of expertise for me), a lot of it is based on "cycles" -- takeoffs and landings -- as that's considered the time of some of the greatest stress on the airframe.

FWIW, while all the BUFFs in service are older than I am, they've all also had their entire tail assembly and wings replaced.

-Kevin
 
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