Re: Reliability of gas turbine engines

Date:         11 Jan 98 03:24:54 
From:         Seth Dillon <bdillon1@mindspring.com>
Organization: MindSpring Enterprises
References:   1
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CQuaranta wrote:
> I was reading the NTSB aircraft incident/accident reports and came across a
> number of instances of "uncontained engine failure" - supposedly either a
> turbine, compressor or fan blade seperates and punctures the engine housing.
>
>     What is the approximate rate of these events in terms of events/hours of
> operation?

An uncontained engine failure is an extremly rare event.  At a major
airline (500+ a/c fleet) 2 or 3 a year on a single engine type would be
enough to start a minor panic.

Gas turbine engines are incredibly reliable, at the airline I work for
mtbr for all engines is around 6000-8000 hours.  One RB211-524B4I ran in
excess of 25,000 hours. ( thought the RR rep was going to cry when we
had to pull it).

Engines are removed for a variety of reasons, life limited parts, fod,
gas path deterioration, burned or eroded blades, egt limited, etc.
These are caused by normal wear and tear, and are usually transparent to
the crew as the engine will still make TO power. Fuel consumtion will be
a little higher, egt will be a little higher, vibes might be higher,
etc. but all within allowable limits.  Allowable damage limits are in
the maintenance manual and when these limits are reached, or performance
has degraded sufficiently, off it comes.  A UCF is a different thing.
It should not happen and the reason is researched extensivly untill a
root cause is identified and corrected.  These are taken very seriously
by the operator.

Sorry I can't provide hard numbers, but I hope this helped.

-Seth