"Mortimer Schnerd, RN" mschnerdatcarolina.rr.com wrote in message
...
Matt Barrow wrote:
The chances of both systems failing on the same flight are much less
than
any one system... and even there failure is an uncommon event. But as
others have noted, you can add redundant instruments and even backup
sources.

Of course, the vacuum system is, IIRC, about 5-10 times more likely to
"take
a dump".


While that may be, I've lost an attitude indicator once, a vacuum pump
once, an alternator once and a fan belt once. A limited history but it's
running 50/50 in my book.

How did you lose the AI?


Of course, that means almost 2700 hours where nothing broke.


Like the adage, "...hours of 'boredom' followed by minutes of stark terror".

Note, that losing the vac pump and the AI would have been of little
consequence with an AI with battery backup. My old bird had a EAI with
battary and the vac AI was my secondary. Also, dual alternators is becoming
the norm in the new generation aircraft.