Re: Jet Engine Containment

From:         Steven Foister <steve.foister@gecm.com>
Organization: GEC-Marconi Avionics Ltd.
Date:         04 Aug 96 16:44:54 
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One of the certification tests required for all turbofans involves
blowing a small charge near the root of a fan blade whilst the engine is
in operation, causing it to detach.
For the engine to pass the test, the blade needs to be fully contained.
For the new large turbofans, this is an extremely demanding test. Kevlar
is used as part of the containment because of its high tensile strength
and low weight, and Rolls-Royce and Pratt&Witney have both used plenty
of it on their engines to pass this test.
GE however have a much heavier fan blade, which is more difficult to
contain. Last I heard (January) their engine for the B777 had still not
passed this test. They were trying to get a test which involved
detonation half way up the blade (much less demanding) accepted instead.
I believe that the GE90 engine is actually only operating at present on
several such temporary waivers. Which would make me think twice about
getting on a (GE-powered) BA 777.
Anyway, I am sure that someone from GE will write in and refute me on
that. Some of your neighbours at Iowa State are also likely to know more
on this than I do.

Finally, the reason for this test is the damage that a detached blade
could do. But what about turboprops?
Steve