Windmilling Prop & Vacuum Pump

No Such User wrote:
In article et,
Matt Young wrote:

during descent through the clouds, or will the gyros keep spinning fast
enough long enough to make the vacuum pump irrelevant?


I question the wisdom of relying on an instrument that you already know to
have failed.

What makes you think it has failed? If the vacuum guage still shows a vacuum,
then the gyro's got to spin (unless you are unlucky enough to have a second
failure of the vacuum system at the same time that the engine crumped).

What I've never understood is why there isn't more obvious indication that
there is no power (vacuum or electric as required) going to the instrument.
Jeez, the VOR which isn't as essential to instrument flight has a better
indication that it's not on.