Re: Descent Calculator

Date:         29 Nov 97 15:40:03 
From:         John Weiss <John.R.Weiss@Boeing.*NOSPAM*.com>
Organization: Boeing Commercial Airplane Group
References:   1 2
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> In article <airliners.1997.2688@ohare.Chicago.COM>, (Ted Landy) wrote:

> >I am trying work out how to create a small program to calculate
> >descent  profiles for aircraft to load into a handheld computer.
> > I want to be able to enter height, speed, wind component and weight
> >to come up with a distance.
> >Originally I thought I could just enter a L/D ratio and presto come
> >with an answer. Unfortunately for me it is not so easy. For a given
> >IAS on descent the L/D seems to constantly change (increase).
> >
> >Does anyone know of any useful formulas, available programs or have
> >suggestions that may be of use to me?

It depends on what you're trying to do.  For a max range or max
endurance descent, you'd have to find the appropriate Angle of Attack
(which would remain relatively constant) for the airplane in question,
and translate it to airspeed with a weight and altitude/temp factor if
necessary. Then you'd have to put in a correction factor for wind (rule
of thumb I use is add half the headwind component, until max of max
range cruise speed; or reduce by the same until max endurance AOA).

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