Diesel aircraft engines and are the light jets pushing out the twins?

Jim,

Please don't reply in such a way as to make it appear that I said something
that I did not. It was Matt Whiting that made the comment about losing all
engines on a twin being more likely than losing all four. I didn't say
that, and I know that is not true.

Dean
wrote in message
...
In rec.aviation.owning Dean Wilkinson wrote:

True, but the probability of losing all of the engines at the same
time
is greater with only two engines as opposed to four.

Matt

Not necessarily...

There has never been a historical case of a twin engine jetliner
losing both engines at once due to unrelated failures. All twin
engine failures have been due to a common cause; fuel starvation being
the prime reason.

Here are some examples of related engine failures:

A four engine 747 had all four engines flame out at the same time when
it flew into the ash cloud of Mt. Redoubt in Alaska, and only managed
to restart three of them after losing over 10,000 feet of altitude.

A four engine Airbus A340 made a dead-stick landing at Lajes in the
Azores after running of fuel due to a combination fuel leak and fuel
system management problem.

A 767 (twin) made an emergency landing in Canada on a drag strip after
losing both engines due to a miscalculation during fueling.

The probability of an ETOPS plane losing both engines in a single
flight due to unrelated failures is extremely remote. That doesn't
mean it can never happen, but it is less likely than winning the
lottery.

Not quite; the probability of all engines failing decreases with the
number of engines if all engines have the same probability of failing.

Whether or not this will actually happen is highly dependent on the
probability of the individual engine failing.

Since airline engines tend to be well maintained, and hence the probablity
of failure low, one could reasonably say the chances of multiple engine
failures (no common cause) is quite remote.

However, a friend of mine that spent lots of time in B-52s relates the
tale of the time they lost 3 engines (no common cause) during flight
and a fourth engine on final getting "that big piece of crap" back on
the ground.

--
Jim Pennino

Remove -spam-sux to reply.

In rec.aviation.owning Dean Wilkinson wrote:
Jim,

Please don't reply in such a way as to make it appear that I said something
that I did not. It was Matt Whiting that made the comment about losing all
engines on a twin being more likely than losing all four. I didn't say
that, and I know that is not true.

Ummm, I posted a followup to the entire post as received without editing
any previous content.

The depth of the '' characters at the beginning of the lines should show
who said what and my response was to the latest post, i.e. that of Matt
Whiting.

--
Jim Pennino

Remove -spam-sux to reply.

Dean Wilkinson wrote:

Jim,

Please don't reply in such a way as to make it appear that I said something
that I did not. It was Matt Whiting that made the comment about losing all
engines on a twin being more likely than losing all four. I didn't say
that, and I know that is not true.

How do you know this is not true? If I recall correctly, the
probability of independent events occuring simultaneously is equal to
the product of the probabilities of each event occurring. If we rule
out common cause failures such as fuel exhaustion and look at only
random failures, the the probability of all engines failing
simultaneously is the product of the probability of failure of each
engine separately. Assuming that each engine has the same probability
of failure, means that with two engines the probability of both failing
is P^2 whereas with four engines the probability of all failing is P^4.
Since 0=P=1, P^4 will be less than P^2.

As someone else said, the probability of having AN engine fail on any
given flight is higher with more engines, but I believe the probability
of ALL engines failing on a given flight is less with more engines.


Matt

Ernest Gann in "Fate is the Hunter" described one event in which he
lost nearly all power on 3 of 4 out of LGA once, and another time that
all 4 quit simultaneously with a load of passengers over the Pacific.
The first event was caused by the mechanics testing a new type of
spark plug, which they "unfortunately" had time to install on 3
engines. The second was a glitch in the fuel system.