Re: Jet Engine Rev Ups for Take Off

From:         Nik Waalewijn <>
Organization: =:-0
Date:         17 Aug 95 04:58:48 
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Mark Wiklund <> wrote:
>Having watched jet departures from the open air decks at
>Logan airport since a boy, and more recently having done
>much travel, I have always noticced that when a jet
>revs up for take off, it seems to go to half-power
>for a second or two before proceeding to take-off
>power - as if it was a two step process. Is this half-step
>process with all engines, or spooling up engines
>individually, or simply a misperception on my part?

If you would set T.O. thrust immediately there is allways a chance that
the engines do not spool up equally. This can happen especially in the
lower thrust settings and that could lead to a situation where you would
have 100 percent T.O. thrust on one engine while the other one(s) only
have about 60 percent. Offcourse that situation gives a lot of problems
keeping the aircraft on the centerline.

A common procedure is to (manually) set about 70 percent T.O. thrust, let
all engines spool up to that level and then hit a button on the thrust
levers that activates the autothrottle system that will then take care of
setting the correct (full) T.O. thrust.  (automatically).


Nik Waalewijn  <>