It actually happened today!! Vacuum failure in IMC.

skym wrote:
Departed Asheville NC today into IMC enroute to Columbia SC. Well into
IMC and about 6500 MSL the DG started to slowly just start rotating and
the AI started to lean over. Backup vacuum-no help.

As others have already said, I'd appreciate some elaboration on why your backup
vacuum was no help.

I couldn't
believe this was happening in IMC; I only fly it about 5% of the time.
Columbia was just a bit above minimums. I was not prepared to try an
ILS with no operative DG, and most of the GPS approaches at CAE want a
WAAS capable GPS, which my G430 isn't.

Putting aside the anthropomorphism implied by approaches "wanting" a WAAS
capable GPS, I'd like to understand how this figured into your planning. All the
RNAV approaches at CAE have LNAV MDAs, so could be flown with your GPS. Why was
the lack of WAAS a consideration?

Second, I'd like to understand in what way you felt prepared to fly an RNAV
approach without a DG, but not an ILS approach. I'd think the workload is about
the same. Do you think having vertical guidance would be a distraction?

Congratulations are in order for handling your emergency safely and competently!

Dave