Mooney ovation and vacuum system

[Mark89114]

I have a relatively new ovation, to me and had a vacuum pump fail recently.

The issue is that the gauge was reading 3.0" before I started engine, I probably should have realized that was incorrect and I am trying to remember if it ever read less than 3.0".   The vacuum system ran fine until the pump failed enroute about 2 hours.  I did not get the annunciation panel lights at any time except for when pump failed it dropped to 3.0", and no annunciation panel indication.  Maintenance is working on it, but as always I am trying to learn what is going on.  

I do have the maintained repair manuals but they are not with me, otherwise I would look it up.

thanks for your input.  Will let everybody know results of repair.

 

[gsengle]

With King flight director/autopilot? Shame to invest in vacuum system as King is coming out with a solid state replacement for the AI any day now...

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[carusoam]

In my low serial number O1, the vac gauge is an add on by the previous owner...

It is at 0 when the engine is not running.  It also has a back-up vac pump for when the first one fails.  The low vac light on the annunciator panel barely meets the FAA requirement.  This is the reason somebody added one.

If going the JPI Route, Add the vac gauge to it and include alarms for both high and low.

Best regards,

-a-

[StevenL757]

Mark, not sure what your plans are longer-term, but as Greg mentions, the KI-300 digital attitude gyro will be out sometime between Feb and March.  With it, you can legally remove your Ovation's primary and secondary vacuum systems.  Installed cost would be roughly 7.5 to 8k, include vac system removal.  With what you're describing, this route may or may not be more expensive than chasing a vacuum system problem, but the longer term benefits would be far greater.

I believe you have a KI-256 connected to a KFC150, so overhauling this gyro (which is prone to fail frequently), will run you major bucks, hence my asking about longer-term plans.  You could be spending a lot chasing what could be a vac issue or an attitude gyro problem.  I'm going through a major cockpit upgrade shortly, which includes a KI-300 + vac system removal, and am waiting for KI-300 to be released.  A G500 will eventually go in, but I'm doing the project in 2 phases, budget being what it is, unfortunately.  Ping with any questions...happy to help.

[Guest]

February or March is a long time to not have a vacuum pump in the plane.  

Put a new pump on the plane and enjoy it for the next 500+ hours.  The vacuum gauge should read Zero at rest and should run approximately 4.8-5.2"Hg at normal RPM.  A healthy pump will produce rated vacuum at lower RPM's

Clarence 

[Mark89114]

OK, time for an update.  Will leave the update to KI-300 vs Aspen till after this problem is solved.

Maintenance replaced the vacuum pump and filter, coupler was sheared.  But I am still having indication issues, someone else on this forum mentioned that their vacuum gauge would stay at 3.0 and it was traced down to a hose.  I am also having an issue with the annunciator dummy light not working in addition to low 3.0 "stuck" reading.  As I was flying airplane back to my other base, the digital gauge would jump up to 5.3 and flash, but again the annunciator light didn't illuminate.  Meeting with mechanic in next couple of days to see if we can trace it down.  I have the Mooney manuals on CD and they are vague, no mention of a vacuum transducer which I assume is needed to measure vacuum versus just an On-Off switch for the annunciator light (just guessing on this).  Any advice would be appreciated.

 

[carusoam]

The annunciator has both high and low lights... There is a section in the MM for the annunciator itself.

what digital vac gauge are you using and who put the set points in it?

Best regards,

-a-

[rgpilot]

The vac gage does not read below 3.0  When it hits 3.0 it will flash to indicate a low vac issue. At that point your low vac light should be flashing.

[Mark89114]

rgpilot, do you have a reference where it should be at 3.0 (with the Moritz engine gauge package) with engine OFF, i.e. no vacuum?  I have pored through the POH but nothing there.   There is a placard on the instrument cluster which lists range, 4.something to a range of 5.2 which isn't documented, as far as I can tell.  The references in POH all mention a high limit of 5.5 

I certainly don't want to be tracing a problem that doesn't exist, which is sounding more and more likely with the digital readout.  The annunciator light is not functioning at all, i.e the high/low vac light on annunciator panel.  Will test and adjust set points if needed.  

 

[Cruiser]

Mooney service manual section 24-33-00 Warning Circuits

3. High and Low Vacuum Warning Circuit. A switch in the vacuum system controls the vacuum warning light on the annunciator panel. Vacuum below 4.25 IN. Hg. causes the vacuum warning light to FLASH. Vacuum above 5.5 IN. Hg. trips the high-vacuum switch causing the vacuum warning light to illuminate steadily.

[M20R]

I had the same problem a couple of years ago. If you have the Moritz package, then there is a small circuit board that measures the vacuum and sends a signal to the gauge. A small hose is connected from the vacuum system regulator (located behind the pilot's side instrument panel), to a small circuit board located behind the lower center panel right by the pilot's right pedal.  Except for having to crawl under the panel, it was an easy repair.

Edited January 3, 2016 by M20R