On Thu, 12 Oct 2006 17:35:28 GMT, "Steve Foley"
wrote:

"Mxsmanic" wrote in message
.. .
Steve Foley writes:

Basic arithmetic is beyond you too?

1 + 1 = 2.

If the probability of any single engine failing is p, then the
probability of either of two engines failing is 1-(1-p)^2.


BZZZZZZZZZZZZTTT Wrong again...

Let's assume that the probability of an engine failure is an
astronomically high 0.1% or p=0.001. That means that the probability
of the engine not failing is p = 1 - 0.001 = 0.999.
There are 4 possibilities in the sample space, assuming that the
engine failures are independent, which they sometimes are not:

1. no engine fails. p = 0.999 * 0.999 = 0.998001
2. right engine fails p = 0.999 * 0.001 = 0.000999
3. left engine fails p = 0.001 * 0.999 = 0.000999
4. both engines fail p = 0.001 * 0.001 = 0.000001

Adding all these probabilities gives us a total of 1, showing that the
math is correct.

Adding all the probabilities of any kind of engine failure gives us
0.000999 + 0.000999 + 0.000001 = 0.001999

If the probability of engine failure in a single engine aircraft
remains 0.001, then 0.001999 / 0.001 = 1.999, or pretty darn close to
two. Twice the probability of a failure.

However, the case that we're most interested in is the probability of
both engines failing. The probability of that happening is 0.000001,
one thousandth the probability of total power failure in a single.

What this means is that if you fly a twin, you have roughly twice the
chance that you're going to have to use your diligently honed
engine-out skills than if you were flying a single. It also means that
if your engine-out skills are up to par and you can successfully cope
with an engine emergency, you'll have only one thousandth the chance
of a forced landing due to power failure. That's what you're buying
with the extra cost, fuel, and training. That and more load capacity,
speed, and looking cooler than anyone else on the ramp.

RK Henry