Jeff and Doug,

 

I don't remember hearing failure rates expressed in percentages but typically MTBF.  One percent (1%) could mean that only 1% of Cheltons ever fail, or that they work 99% of the time, or something else.  If you think about it, 99% is pretty lousy.  That could mean the Chelton's out of service a couple minutes every flight.  The more features we cram into one box, the failure rate has to climb.  Not like the good ol' days when only one instrument or one radio would quit.

 

So we may disagree on how often something will fail and even whether a certain failure rate is acceptable.  I think the important this is they DO fail, whether it's once a decade or once a month.  Either way, we need to have some backup for WHEN they fail.  Murphy's Law would suggest that whenever the failure happens, it will be at the worst possible time.

 

Mike