From:         Morgoth Bauglir <>
Organization: The Fortress of Utumno
Date:         21 Oct 96 02:51:36 
References:   1 2 3 4
Next article
View raw article
  or MIME structure

C. Marin Faure wrote:
> And if the three engine airplane loses two engine during takeoff,
> it's all over.  But in takeoff, where it's really critical, lose two
> engines on the three engine plane, and you're going to hike home if
> you're lucky.

Technically accurate, if you define takeoff as ending when the wheels
come up.

But everybody trains for two-engines out on a three holer right *after*
takeoff.  It's a required part of the checkride.  You generally lose the
second engine between 500' AGL and 1000' AGL.

> Of the very few problems there are on today's airplanes,
> most of them are caused by a problem in the airplane's sytems, NOT in the
> engines.  An electrical failure is going to have the same effects on a
> four engine airplane as it does on a twin.  Your argument will be that a
> four engine airplane has four sources of electrical power, but so does an
> ETOPS twin.

Still correct, except that a three engine airplane that loses *one* can
maintain a pretty respectable altitude, while the twin starts
"drift-down" right away.  I don't know what kind of altitude a
757/767/777 full of passengers and with 180 minutes of fuel plus
reserves can maintain on one engine - perhaps you could shed some light
on that.  And what happens to the fuel consumption when you get there?
Are you running the remaining engine at its limits now?  I'm quite
convinced that the manufacturers had to come up with book figures
showing that this would work to get certified, but in view of the
"expedited" ETOPS certification of the B-777 (rumor only) I'm interested
in hearing how much faith you have in the process.

And why did Airbus go back to *four* engines for the A-340?