Re: SURGE ON GE90 ENGINE

From:         chuanga@iia2.org (H Andrew Chuang)
Organization: International Internet Association.
Date:         15 Jun 95 01:14:00 
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Followups:    1 2 3
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In article <airliners.1995.759@ohare.chicago.com>,
Drakeal <drakeal@aol.com> wrote:
>
>A surge is the same as an engine stall.

A stall and a surge are not exactly the same.  However, many people do
use the two words interchangeably.

>Most modern jet engines (the GE90 included) incorporate
>variable geometry stator vanes; these contribute to compressor stability
>by regulating the amount of air admitted to the compressor.

It should read most modern two-spool jet engines.  I don't believe R-R's
RB211 and Trent have variable stator vanes (VSV).

>Scuttlebutt says that this incident was due to FOD, or Foreign Object
>Damage.

That was an earlier assessment.  According to Flight International, GE
has fixed the problem by changing the VSV schedule.

>I interpret this to mean that a piece of hardware came loose in
>the engine and damaged the compressor.

No, if it's a piece of hardware then it's DOD (Domestic Object Damage).

>
>Stalls are important in this case, because the GE90 program is trying to
>gain its ETOPS or Extended Twin Engine OperationS, certificate from the
>FAA and CAA.

Again, according to Flight International, BA has no intention of using
the A-market B777 for ETOPS.  BA won't receive its first B-markt B777 until
end of 1996.  Thus, GE and BA still have plenty of time to get the ETOPS.
Two years ago, when UA was about to cancel some B747 and B777 orders,
Boeing refused to allow UA to cancel the B777 launch order.  However,
Boeing agreed to push up the delivery of "long-range" version of the B777.
I believe what they meant by "long-range" was to get early ETOPS.

By now, most of you should have heard the news that the flight test for
GE90-powered B777 has been halted.  The reason is because of a recently
failed bird-strike test.  Nevertheless, Boeing and GE still insist the
first aircraft will be certified and delivered in September.

--
  H Andrew Chuang   chuanga@iia2.org