"Ron Garret" wrote in message
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[...]
and have determined the number of trials (flights) in advance.

No. That statement is true regardless of whether N is known.

Knowing that your chances of having an engine failure are 1-(1-P)^N isn't
very useful information if you don't know what N is.

It's not a useful calculation for the purpose of this discussion.

That is a matter of opinion.

Tell me how I'm going to use the information then. Since you think it's so
useful.

No one knows before they've started flying how many flights they will
make
in a lifetime.

That is not necessarily true. My mother, for example, knows exactly how
many flights in GA aircraft she will make during her lifetime: zero.

For a person who will never make a flight in a GA aircraft, why in the world
would I consider at all how many engine failures she'll experience?

It's like trying to figure out how many live births I'll have in my
lifetime. Duh.

And just in case you're too dimwitted to extrapolate from this example
I'll spell it out for you: one can *decide* on the basis of this
calculation to stop flying after some number of flight because flying
more than that results in a cumulative probability of disaster that
exceeds one's risk tolerance.

Only if they make that decision prior to flying those hours. I haven't met
a single person who has ever done such an analysis of their flying career.
I doubt one exists.

If you can find me one, I'll stand corrected. Otherwise, you are without a
point (I'll refrain from any implication that YOU are dimwitted, just 'cause
that's the kind of guy I am).

Pete