Question about losing a vacuum pump

Timbeck2

Timbeck2

Final Approach
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Nov 4, 2015
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Timbeck2
Okay, my vacuum pump gave up the ghost yesterday. My question is how soon does it usually take for the attitude indicator to spool down? It seemed that as soon as I lost suction, the attitude indicator went wonky immediately but the heading indicator took about five minutes to spool down before it started going wonky as well. I've often wondered if I've had something wrong with the attitude indicator before for other weird indications and had planned on getting it overhauled anyway.

Wonky is a technical term, you can look it up.
 
I've lost a pump exactly once and it doesn't take long. My wife happened to catch the vacuum gage drop to zero and it wasn't more than 30 seconds before the AI was useless. Probably faster except we were in straight and level at the time.
 
I would think it would depend somewhat on the condition of the instruments. A freshly overhauled gyro may take a few minutes to spin down while one that hasn't been cleaned in ages may stop rather suddenly.

DIsalcimer: I'm not an instrument repairman and haven't slept in a Holiday Inn in ages.
 
Either way, I'm overhauling the AI and replacing the heading indicator and of course, the vacuum pump.

In a few more years, I'll have a brand new airplane.
 
It's only money, of course, but if you're replacing both vacuum instruments and the pump, why not get it over with and dump the entire vacuum system and replace with electric AI and DG?

Vacuum systems do 2 things: They suck, and they fail.
 
Because I plan on building an RV-7 and would rather put those in it and keep the Cherokee as it is.
 
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