Re: Performance

From:         snowd@coral.indstate.edu
Organization: Indiana State University
Date:         13 Oct 95 01:30:30 
References:   1
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In article <airliners.1995.1561@ohare.Chicago.COM> ajvdplas@pi.net writes:

>Can anybody tell me if there is a difference in jet and turboprop in
>calculating takeoff-performance. Is the obstructionclearanceheight for a
>jet (25 ft) the same as for a turboprop, or is this height 50 ft. I fly
>a turboprop and i read that somewhere, but in our AOM they still use the
>obstacleheight of 35 ft, so I might be wrong in this.

The requirements which spell out engine-out takeoff performance requirements
is FAR 25, specifically sections 101-129 (I believe).

The 50ft obstacle is a part 23 requirement, while the 35ft height is the
height the aircraft will cross the departure end of the runway, at V2 speed,
with an engine out, the engine out having been detected at V1 speed, and
rotation occuring at Vr speed.

The 35ft obstacle clearance requirement also comes into play in computing
departure area performance.  You must reduce the actual takeoff path (again
assuming an engine out), by .9% (at least for a twin engine, i.e., DC9),
this reduced path must clear all obstacles in the departure path by 35ft.