Hi NG,

If the probability of an engine failing is 0.1, the probabilities for
all engines failing a

1 0.1
2 0.01
3 0.001
4 0.0001


5: not enough information to say. You do not specify that the
probability of an engine failing is independent of the other engines
failing. Fly through a volcano cloud and I bet you'll find that if
one engine fails, the others will too... quickly. Volcanos don't
care about mathematics.

:-)

somewhere along the discussion it was already stated, that there are
engine failures due to common causes. Of course, the probability of all
engines failing due to fuel starvation or a vulcano doesn't change
whether you have 2, 4, or 8 engines.

For independent failurs, get the "one engine" number
down low enough and the "two engine" number will also go down low
enough.

I guess with ETOPS engines, this "two engines" number is already
significantly lower than the probability number for a common cause
making all engines fail on a plane. So the total number for "all
engines fail" is not significantly greater on ETOPS 2-engine planes
than on 4-engine planes.

regards,
Friedrich

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