EricJ

Temporarily Blocking off Vacuum pump?

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So my Attitude Indicator (aka Artificial Horizon, as opposed to my mood ring), crapped out during a trip yesterday.   It is the only vacuum instrument left in the airplane, and the only load on the vacuum pump.   Today we removed the AI to send off to the AI clinic and see if the AI doctors can help it.

Meanwhile, if the turnaround time is going to be significant I may still want to fly the airplane without the AI.   The question is, should I just hook the instrument input air filter to the vacuum manifold or should the remaining location on the manifold just be blocked, like the others all got blocked when the old instruments were removed.    This would mean that the pump is putting vacuum on the manifold, but the manifold is completely blocked off so no air can be pulled through it (except at the regulator).    Right now it's blocked off, but I'm wondering whether it'd be better for the pump to allow more flow through it, or will the regulator do that sufficiently with the manifold completely blocked off?

I figured worst-case if I start the engine and the vacuum gauge freaks out I'll just shut it down, and if it stays in the green the regulator is probably taking care of it.   I was wondering whether there are any more educated thoughts on the matter, though?

 

 

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The vacuum pump is a posative displacement pump, it pumps a volume of air, not a pressure. The vacuum regulator is actually just a controlled leak. So if you block it off it will be working pretty hard. But you are just blocking off the suction side, it can only make a vacuum. If you were to block off the pressure side you could destroy the pump. Your best bet is to hook the filter to the manifold.

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Plug the hose that went into your AI.  The regulator will take up the difference.  Do not plug the intake of the pump itself.  It will overheat and fail.  

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7 hours ago, alextstone said:

Take it to an avionics shop and let a pro handle it

Sent from my XT1585 using Tapatalk
 

That's how all the big problems really start.  ;)

 

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That's how all the big problems really start. 
 
So true, Eric!

Sent from my XT1585 using Tapatalk

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15 hours ago, N201MKTurbo said:

The vacuum pump is a posative displacement pump, it pumps a volume of air, not a pressure. The vacuum regulator is actually just a controlled leak. So if you block it off it will be working pretty hard. But you are just blocking off the suction side, it can only make a vacuum. If you were to block off the pressure side you could destroy the pump. Your best bet is to hook the filter to the manifold.

Currently the manifold lines are all blocked off, so the regulator can still function as long as it can produce enough leak to meet regulation.   If it can't I should be able to tell right away from the suction gauge, in which case the filter line could be put on the manifold where the AI was connected.

The instrument shop is predicting a fairly quick turnaround on the AI rebuild, so I may not need to fly it at all before the instrument goes back in.   It'll be moot in that case.

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