Vacuum indication

shorrick mk2 · March 16, 2015

New year, new niggles…

The Ovation I doesn’t have a vacuum gauge but rather a vacuum “caution light” which either flashes with low vac or lights up steady with hi vac pressure. Mine came on steady intermittently at high rpm. Switching the standby vac on sometimes made it go off, sometimes not, just going off on its own.

Any ideas as to what could cause it – vac pump going bad or something more sinister?

rbridges · March 16, 2015

Not sure. I thought most vacuum failures were sudden.

kortopates · March 16, 2015

Too high of a vacuum would be caused by the vacuum regulator on the manifold; not the pump. First step though would be to put a gauge on it and check. The annunciator could also need adjusting if sensing a high vacuum prematurely; but more likely the vacuum regulator needs adjusting.

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**carusoam** · March 16, 2015

Adding a vacuum guage or connecting it to a JPI is possibly the next step.

My early O's prior owner added the small gauge...

Best regards,

-a-

mooniac15u · March 16, 2015

Adding a vacuum guage or connecting it to a JPI is possibly the next step.

My early O's prior owner added the small gauge...

Best regards,

-a-

What paperwork was needed for that? Just a logbook entry?

**carusoam** · March 16, 2015

15U,

I would expect a full set of documentation to be found in the logs including W&B of the miniature near weightless device...

It is attached to a pretty significant piece of the 'keep the clean side up' system and is worthy of the full documentation.

The O left out two gauges that I would prefer to have. FuelP is the other...

These are mostly good for trouble shooting and recognizing a change before the problem actually occurs.

I guess Mooney thought early owners would prefer the 'service engine' light in place of all the instruments.

Best regards,

-a-

**N201MKTurbo** · March 16, 2015

It can be caused by an old dirty vacuum filter.

mooniac15u · March 16, 2015

15U,

I would expect a full set of documentation to be found in the logs including W&B of the miniature near weightless device...

It is attached to a pretty significant piece of the 'keep the clean side up' system and is worthy of the full documentation.

The O left out two gauges that I would prefer to have. FuelP is the other...

These are mostly good for trouble shooting and recognizing a change before the problem actually occurs.

I guess Mooney thought early owners would prefer the 'service engine' light in place of all the instruments.

Best regards,

-a-

I wasn't asking whether documentation was needed, I was asking about what documentation was needed. Is it a 337 or just a logbook entry?

Andy95W · March 16, 2015

I wasn't asking whether documentation was needed, I was asking about what documentation was needed. Is it a 337 or just a logbook entry?

Depends on how your A&P reads the regs. I would read it as a minor alteration so just a logbook entry. If you intend to REPLACE your vacuum indicator light with the vacuum gauge, THAT would be a very different matter, and I would want to go with a 337 as a major alteration, and probably need a field approval signature to boot.

Weight and balance change is probably negligible, depending on how much the gauge and associated tubing weighs. Even so, the logbook entry should state that.

AndyFromCB · March 17, 2015

This is what I put in the Bravo:

http://www.aircraftspruce.com/pages/in/pressure_uma/uma1suctiongauge.php

Logbook entry

**cliffy** · March 17, 2015

+1 for minor alteration and log book sign off for A&P if just added to lights.

**carusoam** · March 17, 2015

15U,

I wasn't trying to be insulting. That was the best I had to give...

I barely remember what I ate for breakfast, never mind the documentation somebody else took care of in 1994...

Fortunately, the other guys have given what you were looking for..?

The guage looks like the one Andy posted, in the manner Cliffy described.

Best regards,

-a-

rgpilot · March 17, 2015

In cold weather I sometimes get a high Vac light. It usually goes away in a minute or 2 or running the engine.

**Shadrach** · March 17, 2015

This is what I put in the Bravo:

http://www.aircraftspruce.com/pages/in/pressure_uma/uma1suctiongauge.php

Logbook entry

I have one of those and I'm not huge a fan...

**Shadrach** · March 17, 2015

New year, new niggles…

The Ovation I doesn’t have a vacuum gauge but rather a vacuum “caution light” which either flashes with low vac or lights up steady with hi vac pressure. Mine came on steady intermittently at high rpm. Switching the standby vac on sometimes made it go off, sometimes not, just going off on its own.

Any ideas as to what could cause it – vac pump going bad or something more sinister?

Dirty filter, collapsing hose, whatever it is, your vac system is telling you something has changed recently. Your MX needs to find out what that is. I would avoid making any adjustments to the regulator until everything else has been ruled out.

Marauder · March 17, 2015

I have one of those and I'm not huge a fan...

I'm not a fan as well. I replaced my 2" original vacuum gauge with one of these. The first one failed out of the box.

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mooniac15u · March 17, 2015

Thanks for the input on the gauge. I had the UMA gauge on my M20D and it was very handy to have when attempting to use the Precise Flight backup vacuum. I only used the backup vacuum once but it was much easier to reference the gauge than to try to reference the table while setting power.

I would not want to remove my warning light. I think warning lights for critical systems are very valuable, particularly in high-workload situations where you might not notice a change in a small gauge outside your core scan. Unfortunately the warning light doesn't really give me as much information as I would like.

It sounds like I might be able to do this with just a logbook entry. I'll ask my A&P for his thoughts on this as well.

mooniac15u · March 17, 2015

15U,

I wasn't trying to be insulting. That was the best I had to give...

I barely remember what I ate for breakfast, never mind the documentation somebody else took care of in 1994...

Fortunately, the other guys have given what you were looking for..?

The guage looks like the one Andy posted, in the manner Cliffy described.

Best regards,

-a-

-a-

I wasn't insulted. Sorry if my reply suggested that. I'm often very direct with my questions and I forget that some may read it with tone that was not intended.

I seem to recall you are chemical engineer. You must have had to deal with chemists and our lack of social skills. :lol:

Marauder · March 17, 2015

-a-

I wasn't insulted. Sorry if my reply suggested that. I'm often very direct with my questions and I forget that some may read it with tone that was not intended.

I seem to recall you are chemical engineer. You must have had to deal with chemists and our lack of social skills.

No, no! Not another chemist!

And just for the record, I have hung up my molecules...

mooniac15u · March 17, 2015

No, no! Not another chemist!

And just for the record, I have hung up my molecules...

I still work in the industry but I haven't been near a lab in years.

Marauder · March 17, 2015

I still work in the industry but I haven't been near a lab in years.

Me too!

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