I thought I'd get a response to my position that the traditional vacuum AI &
DG with an electric TC is good enough for me, and the list has not let me
down....

Jeff, I have no issue with your claim that an all-electric gyro system
eliminates gyro failures due to loss of vacuum.  I will go a step further and
assert that, if properly implemented (and that's a key point), a redundant
electric power system can be made far more reliable than a vacuum system,
which we should all know will fail someday if not changed prophylactically
beforehand.

My guesstimate for MTBF (mean time between failures) for the vacuum system is
something around 500 hours, based on anecdotal information in the aviation
publications.  I will point out that Airborne now has a wear indicator on
their new vacuum pumps, although I don't know whether the dry vacuum pumps
wear down or fracture for other reasons.  In any event, electrics should be
more reliable IF properly implemented.

However, history has shown that the likelihood of crashing due to a vacuum
failure is tiny compared to other causes, and that was my main point.  Here's
another example -- how many people die in midairs?  Probably more than due to
vacuum failures.  How many Lancairs have TCAS?  Not many.  Wouldn't you
rather put your extra money and weight in a TCAS system than another battery
and $1500-per-each gyros?  Statistically, that's the wiser choice (and no, I
can't afford that either, but wish that I could).

My claim was only that loss of control due to vacuum failures represents a
tiny fraction of the fatal accidents experienced in the 50 years or so since
the configuration became a de facto standard.  Further, my supposition is
that the real problem is not noticing that the vacuum is gone until you're in
an unusual attitude, and that most of us have the skills to fly partial panel
IF we are warned that the vacuum is gone and we cover up the AI and DG before
they spin down (hence the warning system I'm installing).

I recognize that my choice is not the right one for everyone, and actually
would prefer that the antediluvian vacuum system would disappear.  Too bad I
just can't afford it.  That doesn't mean that my airplane shouldn't ever poke
it's nose into a cloud, though.

Thanks for your comments, on this and other issues.

- Rob Wolf