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