Re: Are Two Engine 757 & 767 Jets Dangerous?

Date:         04 Jan 97 03:55:48 
From:         "David K. Cornutt" <cornutt@hiwaay.net>
Organization: Residential Engineering
References:   1 2
Followups:    1
Next article
View raw article
  or MIME structure

This has been a very interesting discussion, but I'm wondering
if it isn't focusing on the wrong things.  If I recall correctly
an article that I read in AW about two years ago, there is
*no* case on record of a scheduled airliner (jet-equipped)
ever suffering two independent engine failures on one flight.
Therefore, it seems to me that crashes stemming from engine
failures can be divided into two categories: multiple failures
with a common cause, and a single uncontained failure that
makes the plane unflyable.  Examples:

Of the first category, two come to mind.  In 1985 (I think)
there was an Eastern L1011 that took off from Miami with
all three engines leaking oil (a ramp technician who removed
oil plugs from the engines, in order to check the oil levels,
failed to notice that the replacement plugs that he installed
lacked O-rings to seal them).  And in 1976, there was a
Southern Airlines 727 that flew through a thunderstorm
and had all three engines extinguished by water ingestion.
In the second category, there's the DC-10 in Iowa that lost
all of its hydraulics after an uncontained engine failure, and
the recent El Al 747 could be added to this list.

Clearly, in neither of these cases does having more engines
turning make any positive difference.  (In fact, in the second
case, it might be argued that twins have a very slight advantage
over three- and four-engined aircraft.)  It appears to me that
much more progress could be made by trying to improve
redundancy among systems that support engine operation,
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.

Comments?

---
David K. Cornutt, Residentially Engineered, Huntsville, AL
email: cornutt@hiwaay.net
I'm a rocket scientist.  I know the difference between an
increase and a decrease.