Re: In the air?

Date:         24 Mar 98 11:38:46 
From:         kls@ohare.Chicago.COM (Karl Swartz)
Organization: Chicago Software Works, Menlo Park, California
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>Some airlines like BA get in the range of 15 to 17 hours/day
>of flight averaged over the lifetime of their 747-400s. This would
>imply that two thirds of their 747-400s are in the air at any one time.

If true, that's pretty impressive, but most of those planes are too new
to have seen their first D check, which will put them on the ground for
a big chunk of time.

I happen to have the NTSB report for UA 811 at hand.  That's the United
747-122 which blew a cargo door about an hour out of HNL on February 24,
1989.  The aircraft was delivered on November 3, 1970, 6988 days or
approximately 160,512 hours before the accident.  At the time of the
accident, the aircraft had 58,815 total flight hours (and 15,028 cycles).
That gives an average daily utilization of 8.8 hours over 18+ years.

>Smaller aircraft on shorter flights and possibly idle overnight
>don't get this kind of flying usage figure - possibly reducing as
>far as 30 to 40%.

That's about right.  The "Aloha Convertible" accident aircraft had a
life of 6928 days (delivered May 10, 1969 and the accident occured on
April 28, 1988) and had accumulated 35,692 flight hours (but a whopping
89,680 cycles) for an average daily utilization of only 5.1.  Amongst
aircraft flying in regular airline service, that's probably close to a
worst case.  I think Southwest actually manages 8-9 hours in the air
per plane.

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Karl Swartz	|Home	kls@chicago.com
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