Vacuum pump failure

[cferr59]

I was flying from KEFK (Vermont) to KPNE (Philly) and had a vacuum failure.   Fortunately, I was in VMC over a mostly overcast layer between 3000-5000 feet.  While I have a G5 AI and a Precise Flight backup system, I decided it was best that I find a hole to descend.  I did some practicing with the Precise Flight to confirm how it worked in case I did need to descend through the layer.  The Precise Flight backup system works off of the delta between the manifold pressure and ambient pressure so it does almost nothing if the throttle is fully open or close to fully open.  I was already aware of  how it worked, but had never used it in an actual vacuum pump failure event. Fortunately, a Mooney is pretty fast so a low power setting still produces acceptable cruise performance. 110 knots isn't amazing, but a 172 can't go any faster.

Just as I was starting to get worried, I found a nice size hole near Soleberg Airport and was able to get down while meeting VFR cloud clearance requirements. 

Well, I installed a new pump today and disassembled the old pump. The only issue seems to be that the shear coupling is sheared.  The vanes and rotor are intact and the pump spins freely.  Pump has 550 hours on it and I could have just replaced the coupler, but I feel more comfortable replacing it with a new pump.

I was fortunate to have backups to get myself out of this situation if needed, but this is a good reminder that you should not bet your life on the vacuum pump.

Descent video:
https://gopro.com/v/QnqzVPWX9o5MP
 

 

 

 

[carusoam]

Great pirep of actual vac pump failure, Cferr!

Odd that the shear coupling failed without an obvious cause, like something jammed...
 

I’m glad you put in the extra effort to test your equipment prior to the possibility of descending into any IMC...
 

We still have some leftover memories of the V-tail being spread around NYC... while VMC wasn’t that far away...

Thanks for sharing the pic.

Got room in the budget for another G5?  

Best regards,

-a-

[cferr59]

3 minutes ago, carusoam said:

Great pirep of actual vac pump failure, Cferr!

Odd that the shear coupling failed without an obvious cause, like something jammed...
 

I’m glad you put in the extra effort to test your equipment prior to the possibility of descending into any IMC...
 

We still have some leftover memories of the V-tail being spread around NYC... while VMC wasn’t that far away...

Thanks for sharing the pic.

Got room in the budget for another G5?  

Best regards,

-a-

Definitely thinking of another G5, but I will not be rid of the vacuum system without replacing my Brittain.  I was willing to enter IMC if needed due to the G5, Precise Flight, and Stratus/iPad backups.  However, I had 3 hours of fuel remaining and would not have entered IMC partial panel unless my fuel situation dictated otherwise.

[takair]

I think all of my pump failures occurred at around 500 hours too and just like yours it always seems to be the sheer coupling.  I can’t quite figure out why, accept rotations seems stiff.  I have rebuilt one for use as a ground based pump and it seems to work well enough.  I had assumed oil got in it and gummed things up, but I never found obvious contamination.  Starting to wonder if the coupler is the week link (no pun intended) or if it is more stressed due to vane wear, or is it truly 500 hour contamination.  Like yours, I always thought the vanes would have gone another 500 hours.  

[carusoam]

Another thing to be familiar with... is the limitations of the precise flight device... (Based on cylinder vacuum... not their pump system in the back...)

near sea level, you set the MP low enough to generate the proper vacuum differential...

It can be problematic if you need to climb or stay above mountains...

PP thoughts only, not a mechanic...

Best regards,

-a-

[cferr59]

1 minute ago, carusoam said:

Another thing to be familiar with... is the limitations of the precise flight device... (Based on cylinder vacuum... not their pump system in the back...)

near sea level, you set the MP low enough to generate the proper vacuum differential...

It can be problematic if you need to climb or stay above mountains...

PP thoughts only, not a mechanic...

Best regards,

-a-

Definitely is important to understand that.  I have been aware of how it worked and as a flat-land pilot, I was comfortable with the limitations.  I did want to test it out before any possibility of using it in IMC however.  If land is 5k+ MSL, you need to think about if it would work you; it might not.  A failure in a Mooney is fortunate because it doesn't need a lot of power to cruise slow.

[cferr59]

12 minutes ago, takair said:

I think all of my pump failures occurred at around 500 hours too and just like yours it always seems to be the sheer coupling.  I can’t quite figure out why, accept rotations seems stiff.  I have rebuilt one for use as a ground based pump and it seems to work well enough.  I had assumed oil got in it and gummed things up, but I never found obvious contamination.  Starting to wonder if the coupler is the week link (no pun intended) or if it is more stressed due to vane wear, or is it truly 500 hour contamination.  Like yours, I always thought the vanes would have gone another 500 hours.  

Same situation.  There does not appear to be any contamination and the pump looks perfect inside.  I'm also going to rig it up as a ground pump for any testing I might need to do. It will not fly again.  I am not that brave...

[EricJ]

The coupler is the weak link by design, and if it shears I wouldn't reinstall that pump unless it only ran the step or the speedbrakes or something.   Something made it shear.

[carusoam]

Nice pirep for the tempest tornado vac pump, nosky!

Thanks for sharing it...

Best regards,

-a-

[milotron]

3 hours ago, cferr59 said:

I was flying from KEFK (Vermont) to KPNE (Philly) and had a vacuum failure.   Fortunately, I was in VMC over a mostly overcast layer between 3000-5000 feet.  While I have a G5 AI and a Precise Flight backup system, I decided it was best that I find a hole to descend.  I did some practicing with the Precise Flight to confirm how it worked in case I did need to descend through the layer.  The Precise Flight backup system works off of the delta between the manifold pressure and ambient pressure so it does almost nothing if the throttle is fully open or close to fully open.  I was already aware of  how it worked, but had never used it in an actual vacuum pump failure event. Fortunately, a Mooney is pretty fast so a low power setting still produces acceptable cruise performance. 110 knots isn't amazing, but a 172 can't go any faster.

 

 

 

Interesting on the Precise Flight System. I have never actually tried mine before as I was unsure of it coming back to the 'normal' vac source without issue.

Had you ever operated that standby system before the failure or was this the first time?

 

I really should try mine out at some point before ever using it in anger.

 

 

iain

[cferr59]

3 hours ago, milotron said:

Interesting on the Precise Flight System. I have never actually tried mine before as I was unsure of it coming back to the 'normal' vac source without issue.

Had you ever operated that standby system before the failure or was this the first time?

 

I really should try mine out at some point before ever using it in anger.

 

 

iain

It can be tested on the ground by pulling power to idle where the vacuum is at the low end of the range, then noting the increase in vacuum by turning the backup system on.  I only do this check if I expect to enter IMC.

[Guest]

6 hours ago, milotron said:

Interesting on the Precise Flight System. I have never actually tried mine before as I was unsure of it coming back to the 'normal' vac source without issue.

Had you ever operated that standby system before the failure or was this the first time?

 

I really should try mine out at some point before ever using it in anger.

 

 

iain

When these were installed, they were supposed to be flight tested with the vacuum pump disconnected.  Then a placard was filled out with altitude, rpm and MAP required for a specific vacuum value.

Clarence

[TonyK]

Mine had a coupling failure but disassembly revealed something more serious.  I also like that the new one came with a caliper to check the vane wear.

[steingar]

How much is it to install a backup vacuum source in one of our Mooneys?  Is it cheaper to get a couple G5's and bail on the vacuum altogether?

[RobertGary1]

2 hours ago, steingar said:

How much is it to install a backup vacuum source in one of our Mooneys?  Is it cheaper to get a couple G5's and bail on the vacuum altogether?

Vacuum is pretty cheap. I have two redundant GI-275's but also kept the vacuum indicator because its such a cheap way to have attitude information. Plus since they are both legally primary I can launch if any one of them is dead. So I don't see a reason to get rid of the vacuum. I do see a good reason to have a good backup though.

-Robert

[Andy95W]

2 hours ago, steingar said:

How much is it to install a backup vacuum source in one of our Mooneys?  Is it cheaper to get a couple G5's and bail on the vacuum altogether?

You can buy a brand new standby vacuum system for $699, or about $200 used. Will take about 4-6 hours to install it.

But in this day and age, the better question is why?

[steingar]

3 hours ago, Andy95W said:

You can buy a brand new standby vacuum system for $699, or about $200 used. Will take about 4-6 hours to install it.

But in this day and age, the better question is why?

Because 1 AMU is a tenth of the ten AMUs it costs to ditch the vacuum.  But thanks for the numbers.  I ever get the IR this will be high on my list.

[RobertGary1]

27 minutes ago, nosky2high said:

Instead of spending the money on a backup vacuum system, why not replace the turn coordinator with an electric attitude indicator with inclinometer? My $0.02

Usually because the turn coordinator drives the auto pilot.

-Robert

[carusoam]

13 hours ago, M20Doc said:

When these were installed, they were supposed to be flight tested with the vacuum pump disconnected.  Then a placard was filled out with altitude, rpm and MAP required for a specific vacuum value.

Clarence

There is an example around here where @Marauder has filled all the data in for his Precise Flite system from back in the day... before the pair of Aspens got installed...

It is really good to have the data To know what altitude and MP settings it works at...
 

If it is your only plan B, it would be like flipping a coin... The TC may be only good on smooth days for back-up...

So... a Dynon portable would be the place to spend your excess AMU... D2 or D3... or something similar...

Best regards,

-a-

[Bravoman]

If you rely on a vacuum system it’s best to have an electrically operated backup like the Aerosafe Guardian. I had a Precise Flight system in my Piper and replaced it with the Guardian shortly after buying the plane. You just flip a switch and it works great.

[mooneyflyer]

On 10/12/2020 at 7:18 AM, steingar said:

How much is it to install a backup vacuum source in one of our Mooneys?  Is it cheaper to get a couple G5's and bail on the vacuum altogether?

I have an electric backup pump I will sell you for cheap... Also a brand new SigmaTek if you want for cheap also

[0TreeLemur]

I highly recommend the AV-20S timer, which includes a MEMS-based AI, if you have a 2-1/4" hole available in  your panel.   I have it showing the AI view all the time I'm in IMC, and so far it always agrees with the vacuum based AI.  As a backup, I believe it will save your day and help with partial panel ops.   The other thing that I really like about it is that when connected into the pitot-static system, it notes the time that you takeoff and starts a flight timer.  Very useful for switching tanks.   It has some negatives too.  The TAS is not calculated correctly, the AOA sensor is worthless, and the G-meter is distracting.  I have all those turned off in the setup.   The timer functions are great.  The backup AI is a winner.

When the company sold to uAvionics, I contacted them about the TAS issue, and was told that a fix was in the works, but I haven't heard anything since then.  I wish they would issue an improved firmware.   Since it has an external temperature probe and pitot/static info, calculating TAS should be straightforward.   Hell, they could even make it possible to enter a table to give calibration values to output CAS.   I wish they would....

 

[Mooneymite]

12 hours ago, Bravoman said:

If you rely on a vacuum system it’s best to have an electrically operated backup like the Aerosafe Guardian. I had a Precise Flight system in my Piper and replaced it with the Guardian shortly after buying the plane. You just flip a switch and it works great.

 

Does anyone practice "partial panel" anymore?  It used to be the standard backup to vacuum IA/DG instruments and certainly could be a valuable skill to maintain in this age of "all glass" when the glass goes "all dark".

[201Mooniac]

1 minute ago, Mooneymite said:

 

Does anyone practice "partial panel" anymore?  It used to be the standard backup to vacuum IA/DG instruments and certainly could be a valuable skill to maintain in this age of "all glass" when the glass goes "all dark".

Practice it, yes, but it is hardly a challenge anymore.  Last weekend I "failed" my G500TXi and flew an approach on my G5.  I didn't sweat it one bit, it was easy as it can be.

[Mooneymite]

25 minutes ago, 201Mooniac said:

Practice it, yes, but it is hardly a challenge anymore.  Last weekend I "failed" my G500TXi and flew an approach on my G5.  I didn't sweat it one bit, it was easy as it can be.

The partial panel I was referring to was "needle, ball, airspeed", not just adjusting the scan to a different piece of glass.