Re: B767 FMC

From:         geohull@ditell.com (George Hull)
Organization: DirecTell L.C. - Park City, UT. - 1.801.647.0214
Date:         07 Apr 95 03:09:13 
References:   1 2
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In article <airliners.1995.350@ohare.Chicago.COM>, fmcdave@aol.com
(FMCDave) wrote:

> Fuel at destination is calculated by the FMC Performance function.  It
> uses the cruise altitude, wind profiles, and calculated speed (such as
> ECON) to perform the integration.  It uses the lateral flight plan for the
> distance and if there are any discontinuities then a direct line distance
> between the discontinuous parts are used.  This probably happens most when
> you have not entered an arrival.
> 
> The biggest impact to the fuel at destination is the accuracy of the wind
> model.

Additionally, if the calculated fuel differs from the indicated amounts by
a predetermined amount the pilots must choose which value is most accurate
. . it might be the first indication of a leak in the fuel system.

And the FMC uses a "cost index" to determine the speed to use for cruise
flight.  That value is supplied by the company and is a way to prioritize
the relative costs of fuel and other costs such as the crew.

Geo.