Re: Engine questions.....

Date:         01 Oct 97 19:57:50 
From:         Pete Mellor <>
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Mark Johnston <> on Sun Sep 28 12:09:00 1997,
gave a very neat short explanation of "compressor stall".

Mark: Would you please comment on the effect that the angle of
attack of the aircraft (which defines the angle of the oncoming
air to the line through the axis of the engine) has on the
occurrence of compressor stall?

I am curious, since compressor stall was at one time being
touted as a contributory factor in the inability of the pilot
to gain sufficient power to raise the aircraft (A320) above
the trees at Habsheim. It hit the trees at an AOA of around
15 degrees. (The compressor stall hypothesis has since been
refuted, although there was some prima facie evidence in the
form of a report of characteristic noises from an eye-witness
on the ground.)

Following the crash, it was reported that modifications were
made to the settings of the variable stator vanes with a view
to improving engine performance at low speeds. (Airbus denied
that any modifications were safety-related, and stated that
they had nothing to do with the accident.)

I would be similarly interested in anything you could tell me
about the effect of the VSV settings on engine performance and
propensity to compressor stall.


Peter Mellor, Centre for Software Reliability, City University, Northampton
Square, London EC1V 0HB, UK. Tel: +44 (171) 477-8422, Fax: +44 (171) 477-8585