On Feb 3, 12:02*pm, a wrote:

Gotta check pretty often, have had vac pump failures in actual IMC --
don't want to chase a spinning down gyro

It may be just bad luck, I doubt I spend 25% of the time in actual
IMCs, but have had two vac pump and one alternator failure in actual
(but soft IFR approaches) IMC

I've had one fail in IMC, but it wasn't the pump, but the vacuum pump
regulator that failed in IMC in my prior Sundowner. Caused my AI to
display an extreme pitch up on a climb because it was pegged opposite
of failure. My ASI idicated a steady 90 knots with a steady RPM so I
knew something was wrong with AI right away.

I advised ATC that I was going to use GPS ground track for headings.
I then reverted to my partial panel skills ignoring vacuum system
instrumentation. Turned out DG wasn't affected but I wasn't leaving
anything to trust it.

On VFR flights other then checking the DG accuracy when I lined up on
the runway, until now, I never crossed checked it at the end of the
turn as I had assumed it worked if it worked on the ground (runup
normally would catch this as well as last minute check on runway
before blast off).

As you can see what assume does. DG was iffy in performance
(digressing by 10 degrees) but didn't misbehave that much on my turns.

I tend to be more lax on instrument scans (CROSS CHECKING) on VFR
flights only because my eyes need to be outside the window! So even
if this happened tomorrow, realistically I don't think I would have
caught this mistake.