Re: Aircraft Availability

From: (FMCDave)
Organization: America Online, Inc. (1-800-827-6364)
Date:         01 May 95 02:44:03 
References:   1
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  or MIME structure (Edgar Zapata) wrote
>Availability as MTBF/(MTBF+MTTR) or operational availability as
>MTBF/(MTBF+MDT) must be a statistic airlines use for their fleets or
>for a particular aircraft.  Having exhausted any other avenues would
>anyone know how an airline figures this number or what it might
>typically be for say, American 727's or Northwest DC-10's?

>The subject is of interest in the spacecraft industry now; in particular
>the RLV project by NASA/Industry (my concern here...)

I work for an airframe manufacturer (in avionics engineering) and it is my
experience that MTBF/MTBUR is calculated on a system by system basis.  The
number we track at the aircraft level is dispatch reliability.  Basically,
you count the number of departures and compare it to the number of delays
(due to equipment) which exceed 15 minutes.  This number can vary
dramatically between airlines for the same equipment.  Basically, this is
due to maintenance procedures and capability (along with how they perform
their spares logistics).  I think the number for the 747-400 (fleet-wide)
is about 96-98%.