Date: 05 Jan 97 03:22:36
From: firstname.lastname@example.org ( 0 Falke_Charlie phone dist )
Subject: Re: Are Two Engine 757 & 767 Jets Dangerous?
> This has been a very interesting discussion, but I'm wondering
> if it isn't focusing on the wrong things. If I recall correctly
> and improving containment of engine failures. Trying to
> further mitigate the already-improbable case of multiple
> independent engine failures doesn't look like a winning strategy.
Interesting points and questions.
In airplanes and engines that are designed for ETOPS, considerable
care is taken for common mode and fraternal damage. The situation in
the DC-10 where all three hydraulic system's lines were right next to
each other wouldn't cut it for ETOPS.
As an example, the electrical cables that carry the throttle
position signal in an ETOPS twin typically run well apart from each
other for each engine, and for each channel of the dual channel
electronic engine control. A typical route on one side would be that
one channel will run up the leading edge and the left side of the
fuselage, and the other up the trailing edge, and around over the
cabin and up the right side.
We even have to design the fuel and oil plumbing so that if the
right engine throws a fan blade under the fuselage at the left engine,
it won't cut any of the lines. (This means the lines either go on the
left side of the engine, or higher up.) This is, of course, after we
have succesfully demonstrated explosively releasing a fan blade and
containing it. Boeing runs "blade out" tests as well, which also
assume that we've failed ours, and blow a simulated fan blade through
a fully pressurized fuselage, and show that the tear doesn't
Containing disks (much heavier than blades) doesn't seem
practical. The approach for these is to run pacer endurance engines to
put more cycles on a test engine than anybody else's has, and
establish a safe life.
Charlie Falke Pratt & Whitney
System Test Team Leader C/O Boeing Comm AP grp.