Vacuum Failure with Dual Pumps

L

Louie1975

Well-Known Member
What would cause a vacuum system failure in an airplane with 2 vacuum pumps, say, in a C172R? As a follow up question, what would cause a partial panel situation in such an airplane?
 
Louie1975 said:
What would cause a vacuum system failure in an airplane with 2 vacuum pumps, say, in a C172R?
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  • Engine failure followed by a battery that runs out of power.
  • Broken hoses.
  • Two broken vacuum pumps.
  • Engine fire melting a vacuum hose.
  • Underpants gnomes.

As a follow up question, what would cause a partial panel situation in such an airplane?
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  • Loss of two vacuum pumps.
-mini
 
Before anybody says you are not going to lose two vacuum pumps.....It happened to me in IMC. Lost one pump and a few minutes later lost the other.
 
wjmiller3 said:
Before anybody says you are not going to lose two vacuum pumps.....It happened to me in IMC. Lost one pump and a few minutes later lost the other.
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The mean time between failure for dry vacuum pumps is roughly 500 hours.

If you have two pumps that were installed around the same time...
 
I still think dry vacuum pumps are a terrible idea and am amazed that such technology was accepted as THE way to do things in aviation.
 
trafficinsight said:
The mean time between failure for dry vacuum pumps is roughly 500 hours.

If you have two pumps that were installed around the same time...
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I don't agree with the first, but I do agree with the second part and the post about the regulator/shuttle valve. 500 is what the manufacturer recommends as a way to mitigate stupid lawsuits like the Carnahan case. I seem to recall a "Partial Panel" task on the IR PTS, but lets hang the people who build the pumps.

The pumps can last longer, but they have to put a limit on them, like the hour and months in service for an engine. I've seen the pumps in the R, Tempest I think, last well over 1500 hrs. In rental/training aircraft it's hard, if not impossible, for the pilot to know the time on the pumps. If I owned a plane with a single vac and did any IFR flying, you'd better believe the pumps would go at 500 hrs.
 
deadstick said:
I don't agree with the first, but I do agree with the second part and the post about the regulator/shuttle valve. 500 is what the manufacturer recommends as a way to mitigate stupid lawsuits like the Carnahan case. I seem to recall a "Partial Panel" task on the IR PTS, but lets hang the people who build the pumps.

The pumps can last longer, but they have to put a limit on them, like the hour and months in service for an engine. I've seen the pumps in the R, Tempest I think, last well over 1500 hrs. In rental/training aircraft it's hard, if not impossible, for the pilot to know the time on the pumps. If I owned a plane with a single vac and did any IFR flying, you'd better believe the pumps would go at 500 hrs.
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Yeah, some of them do last longer... that's why it's a mean time between failures. The amount of pumps that are 200 or 300 hours in that I've changed tells me that it's not unreasonable. If the pump has 500 hours on it, in my opinion, it's running on borrowed time.

Sigmatek has 2 pumps I'd like to try out sometime, one has an aluminum rotor and supposedly lasts longer. The other, which I think is a great idea but is pretty expensive, is a piston type pump that supposedly has a 2000 hour warranty.

Other than that I'm not sure why they didn't go back to wet pumps... seriously, they last.
 
Personally, I worry more about losing things like deice boots with the loss of a vacuum system than I do losing an AI and/or DG.

-mini
 
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