"mbremer216" wrote in message
. ..
Passing through 7500. Southeast bound past the London VOR. A whiff of
oil smell in the cockpit that passed as quickly as it came. Then, the
suction needle drops from it's usual 5.0 to nothing at all.

Interesting that you got a sniff of oil to portend the failure, I'll have to
file that one away. The pumps are referred to
as "dry" and "wet" can I ask which one you had? I imagine the bearings are
sealed and oiled even in the dry pump?

Our club airplanes have backup electric suction, however the 172s don't have
annunciator lights for the vacuum and I am
self conscious about the practical time to diagnose a failure before
adjusting my scan or activating the backup. I would
second Mr. Macklin's comment about the electric AI. I believe that would
be a more important safety net than
some of the other expensive accoutrements I have invested in over the years.
I have heard 400 hrs cited as the MTBF of
the pumps and we replace them out of superstition on a regular calendar
schedule.

The only failure I've ever experienced was on-top and the layer was thin
enough that we could see the city lights below so the descent on turn and
bank and airspeed was a non-event. I'm not sure I'd do as well in bumpy IMC
if
it wasn't preceeded by an instructor sticking a sink stopper over the AI.

As a side note, I've experimented with taking a photorealistic image of the
AI and cementing it to the temporary instrument
cover and for me it was quite distracting to have to scan past even an
artificial canted horizon.

Good show Mike and thanks for posting.

Todd