Re: Trent 800 woes

Date:         03 Oct 97 01:18:31 
From:         Chuanga@cris.com (H Andrew Chuang)
Organization: Concentric Internet Services
References:   1 2
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In article <airliners.1997.2367@ohare.Chicago.COM>,
Malcolm Weir <malc@mci2000.com> wrote:
>
>Flight Internation 10 - 16 September states:
>
>"Pratt & Whitney says that an upgrade effort to counter reliability problems
>on more than 1,600 PW4000 engines is showing results, with a 'dramatic
>reduction' to in-flight shutdown rates.
> The upgrade effort, known as the Number 1 reliability programme, involves
>around 100 service bulletins.  More than 70 PW4000 customer airlines have
>incorporated around 80% of the improvements into their engines, says P&W.
>It adds that the 12-month rolling average in-flight shutdown rate for the
>fleet has dropped from 0.014% in January 1997 to 0.008% in August as a
>results".

The 94-inch PW4000 (which powers the A300/310/B767/B747/MD-11) has had a
poor reliability record relative to the RB.211 and CF6 engines,
especially the latter.  Thus, the Reliability 1 program was established
to address the issue.  However, both the 100-inch PW4000 (for the A330)
and the 112-inch PW4000 (for the B777) have very respectable record,
definitely much better than the Trent 700 and 800.

>Specific to the 777, "P&W confirms that it is replacing the low-pressure
>turbine (LPT) stage-five vanes from PW4077 engines in service on Boeing 777.
>'We saw this in validation tests for ETOPS, and we saw some areas in the LPT
>vane that needed improvement."

All engine companies constantly provide performance imporvement packages
just like the airframers.  Durability is important but reliability is
perhaps more important.  Maintenance associated with durability issues
is usually predicatable and schedulable.  However, the same cannot be
said about incidences associated with reliability issues.

>So perhaps Delta's selection of RR is as good as P&W?

It's only my opinion.  You're certainly entitled to your opinion.

>Particularly since
>the Trent's problems seem to be self-identifying (i.e. oil temperature
>climbs through the roof), while some of the PW4000 problems involved
>modifications to the leading edges of the fans due to cracking after foreign
>object impacts...

The Trent 700/800 is supposedly a derivative engine, hence, it should
be a more mature engine in the field and a less risky choice for airline
customers.  However, the Trent 700/800 seems to have encountered even
more field problems than the GE90, a brand new engine which was expected
to have more teething problems.  Most airlines love the economics of
flying twins.  However, Cathay Pacific seems to hate twins.  Perhaps, the
fact that CX only has Trent-powered twins (the A330 and the B777) is not
a coincidnece.