Re: airliner maintenance

From:         kls@ohare.Chicago.COM (Karl Swartz)
Organization: Chicago Software Works, Menlo Park, California
Date:         01 Jun 94 14:35:01 
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>For every hour that an average jet airliner spends flying, how
>many hours of maintenance work is required?

A friend sent me a copy of the NTSB report on the United 747 operating
flight 811 that blew a cargo door an hour out of Honolulu.  (Thanks
again, Tony!)  Appendix C of the report details the recent maintenance
history of the aircraft. This is specific to both United and a 747-100,
but is probably a decent approximation of most large commercial trans-
ports.  (One of our readers works for Delta in this area, and hopefully
will be able to offer another perspective.)

     Type of		Maximum
    Inspection		Interval
    ----------		--------

    Service No. 1	To be accomplished on through flights or at
			trip termination whenever time is less than
			12 hours per Maintenance Manual Procedures BX
			12-0-1-1.

    Service No. 2	65 hours
			(Aircraft with layover of 12 hours or more
			will receive a Service No. 2 not to exceed 65
			hours between checks.)

    A Check		350 hours

    B Check		131 days

    C Check		393 days

    MPV Check		5 years

    D Check		9 years

The Service No. 2, I believe, is mostly steam cleaning of the interior
and generally spiffing things up.  Service No. 1 is probably the litter
pickup and such.  I'm not sure if either of these include any real work
to the engines or airframe.  I'd expect that one of them might include
at least some basics like checking the engine oil, though this may just
be done as needed between A Checks.

PS: Since it seems to be a common question, this aircraft is indeed
    still flying for United, though they reregistered it from N4713U
    to N4724U after the accident.

--
Karl Swartz	|INet	kls@ohare.chicago.com
1-415/854-3409	|UUCP	uunet!decwrl!ditka!kls
		|Snail	2144 Sand Hill Rd., Menlo Park CA 94025, USA
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