First Vacuum Pump failure

iceman21

Well-Known Member
There I was 20 miles from CMI just tooling along waiting for vectors. Doing my scan and I see what looks to be the "Low Vacuum" light. The sun is behind me, so the panel is lit up, and the light looks 'sort of' on. I shrug my shoulders and take a look at the AH and DG and everything seems normal. Take a look at the suction gauge and sure enough pegged at the bottom. Just to verify that I did the "Low Vacuum" light I cupped my hands around the light. Call ATC and let them know because its the law. Then rummage around the cabin for something to cover up the instruments with. About 5 minutes later I look the AH and it has fallen to the side. Luckily I was in severe VFR weather and had the field in sight.

All in all no biggie. Flew it back VFR to PWK scudrunning the whole way. Had a blast.
 

Mavmb

Well-Known Member
Interesting story there. I've never had any instrument failures. How long did it take for the DG to fail? What kind of plane were you flying? It's a good thing you were able to stay in VFR the whole time.
 

iceman21

Well-Known Member
Flying a 172

You know I didn't even take a look at the DG. The AH was what I noticed first so I just covered both of them up.
 

iceman21

Well-Known Member
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The fact that the engine vacuum pump went out did'nt bother me as much as the thought of "What if something else goes out!" Thankfully, I too was in Severe VFR!

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That is exactly what went through my head. I found myself fixating on the engine instruments after that (all 2 of them!)
 

davetheflyer

New Member
I had my first vacuum failure on a solo x-c just after I got my private license. I was so green that it was pretty scary to me, even though it was good VFR.

I've also had two AHRS failures since I've been an airline pilot. The AHRS provides input to the attitude and heading intruments in a glass cockpit airplane. It's a lot simpler to fix. You just go into reversionary mode and run your instruments off the other pilot's AHRS. Thank goodness for redundancy!
 

iceman21

Well-Known Member
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Thank goodness for redundancy!

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Kinda like the dual vacuum pumps on the 172R models.

Personally I would like to have a slaved HSI to work with, then I wouldn't have to worry about that damn gyro precession
 

sxauer

New Member
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Kinda like the dual vacuum pumps on the 172R models.


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Actually, the way that it was explained to me by an A&P when my college got the new 172s in is like this: They will basically very close to the same time. Because they both have the same number of hours on each pump, and the pumps are the same age/hours. I dunno, he was probably wrong, but it does make some kind of sense....bah..i need sleep
 

sxauer

New Member
ok...after reading my post it seems that I was on crack or somthing
What I was trying to say is they supposidly will fail very close to the same time. Anyway, I didnt edit my other post so everybody could see my sleep dep post....similar to a crackhead? you make the call
 

davetheflyer

New Member
Of course, vacuum pumps aren't required to be replaced at any point, they simply run until they fail. I see the point that he was trying to make. If they have the same length of life, the pumps may fail at close to the same time.

If one fails, it might be time to think about replacing the other as well.
 

sxauer

New Member
If I owned a new 172, i'd run the pumps untill about 500 hours then change one out....that way you have a spare on hand....i'd probably change my mind if I knew how much they cost....probably about $2,000
 

DrBenny

New Member
If *I* owned a new 172 I would take some of the thousands of dollars I must have lying around my house and put in a backup electrical AI.
 

iceman21

Well-Known Member
Just looked up a price on a vacuum pump online and found one site that lists the part for 172s at 265.00
 
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