Re: interesting ETOPS stats from UAL

Date:         16 Jun 98 02:15:15 
From:         faurecm@halcyon.com (C. Marin Faure)
Organization: NorthWest Nexus Inc.
References:   1 2 3 4 5
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In article <airliners.1998.885@ohare.Chicago.COM>, JF Mezei
<jfmezei.spamnot@videotron.ca> wrote:

> Gerard Foley wrote:
> >   Their minds must be back in the piston engine era, when the take off
> > stress was the major cause of engine problems.

Actually , takeoff had little to do with it.  ETOPS came about as the
result of the 60-minute rule, which is still on the books, incidentally.
This rule was created in the 1950s as the result of several fatal crashes
of twin-engine (piston) airliners which burned up their remaining engine
in an attempt to reach an airport after losing one engine.  The problem is
that a piston engine, unlike a turbofan engine, experiences an increasing
probability of failure as its power in increased.  So a twin-engine piston
airplane flying on one engine at the high power settings required for
continued flight runs a substantially increased risk of losing the
remaining engine.  Jet engines, at least the modern ones, can be run all
day at high power as long as fan, compressor, and turbine speeds
(N-speeds) are not exceeded and temperatures are not exceeded.  As modern
turbofans turned in increasingly impressive reliability statistics during
the early 1980s on planes like the A300, A310, and 767, it was realized
that the old 60-minute was not necessary, and thus ETOPS was born.

C. Marin Faure
  author, Flying A Floatplane