On 1/19/2011 4:45 PM, Jim Logajan wrote:


For independent systems each aircraft is self reliant and equipment and
procedures would have to fail on _both_ for the whole system to fail. Even
though each plane exhibits a 10% failure probability, there is only a 1%
chance that both will not be working at any given collision event because
they back each other up.

Your math is fine, but it appears an independent system, other than the
eyeball, will have 100% failure probability for many years, as I'm not
aware of any device being considered, much less near the testing phase.

There was another interesting optical system offered for sale a few
years ago, but it disappeared. Too bad - it was small and cheap at $1000
to $2000. It worked by comparing successive images, looking for
something that was getting bigger but not moving otherwise.

So, while the math favors an independent system, the reality is we have
several dependent devices that are in service and working. Inelegance
wins the race.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)