Attitude Indicator and Directional Gyro faults

[Mooney-Shiner]

Hello, Esteemed board.

I really appreciate the continuous stream of valuable opinions of MS as we are working on repairing our aircraft to get it to the tip-top shape.   

New chapter in our (my A&P and my) journey is fault with the AI and DG that all of the sudden starting acting up.

My CFI and I were doing some pattern work, when we noticed that the DG is doing a continuous spin and the AI card had sagged and didn't show any accurate readings.  Neither Low nor High Vacuum light was lit though. We played it safe and landed back to the field. I did some taxiing around the airport and noticed that DG no longer responded to any changes in plane's orientation and AI continued to sag.  Now my A&P and I are trying to figure our what could this be. From reading past threads, it seems that we should get a vacuum gage and check the "plumbing" for vacuum at various points to id a potential break in the line.

Are there any other troubleshooting suggestions? 

Note: I recently had avionics shop do a VFR check on my transponder, so they may have interfered with something. 

[ShuRugal]

When was the last time you vacuum filters were changed? If your instrument vacuum filter is clogged, the vacuum regulator will admit air through its filter to maintain the correct vacuum, but it won't do any good because there won't be airflow through the instruments.

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[RLCarter]

Sounds like the vacuum pump gave up the ghost 

[AIREMATT]

Do you have a Standby Vacuum system installed? I just removed mine with the dual G5 upgrade but had a problem after some work in my avionics compartment. The tube was knocked of the standby vac. fitting and was an easy repair once found in front of the pilot side just forward of the fire wall under the avionics access cover. The clamp was loose so it was easily bumped off.

I have all the removed parts from the Precise flight standby system in a box yet too.

I assume the low vac warning light works right? Maybe that would be the first place to look behind if it works and isn’t showing low vacuum. 
Can’t remember where in the system it’s plumbed in relative to the DG & A/I.

[S.C.]

I faced the same dilema this past summer.  I went for the G5 upgrade.  I discussed it with my AP and he was willing to chase the vacuum gremlin if I wanted to pay my way to getting the upgrade.  I'm very happy I went straight for the upgrade.  I do have a Garmin 650 so it’s fully integrated and no glitches.  Avidine makes a great system too.  Look at both and see which makes more sense.  I’m a proponent of modernizing the avionics. 

[Mooney-Shiner]

On 12/3/2021 at 11:07 AM, ShuRugal said:

When was the last time you vacuum filters were changed? If your instrument vacuum filter is clogged, the vacuum regulator will admit air through its filter to maintain the correct vacuum, but it won't do any good because there won't be airflow through the instruments.

Sent from my Pixel 3a using Tapatalk
 

Thank you, ShuRugal!

Looking through the records, it appears that it hasn't been changed since 2013.  I removed it and will replace. Fingers crossed that its the culprit. 

I would like to get 50-100 hrs from this plane before I will decide to start avionics conversions, although I do see the point of losing the vacuum system. 

Edited December 8, 2021 by ukrsindicat@yahoo.com

[RobertGary1]

26 minutes ago, ukrsindicat@yahoo.com said:

Thank you, ShuRugal!

Looking through the records, it appears that it hasn't been changed since 2013.  I removed it and will replace. Fingers crossed that its the culprit. 

I would like to get 50-100 hrs from this plane before I will decide to start avionics conversions, although I do see the point of losing the vacuum system. 

Honestly I don’t. The vacuum system is the cheapest attitude diversity you’ll find. All the AHRS manufacturers have had patches for  software bugs for dual AHRS failure. Software bugs happen and I’ve flown around with two gi-275s that hit a snag at the same time. Garmin issued a patch but bugs will always be there  love my dual gi-275s but I wouldn’t go in the clouds without a backup source of attitude. I kept my vacuum and was lucky I did. Also used vacuum stuff is dirt cheap. 
Not worth saving 5 pounds of weight to lose a great attitude back up. 

[Mooney-Shiner]

2 minutes ago, RobertGary1 said:

Honestly I don’t. The vacuum system is the cheapest attitude diversity you’ll find. All the AHRS manufacturers have had patches for  software bugs for dual AHRS failure. Software bugs happen and I’ve flown around with two gi-275s that hit a snag at the same time. Garmin issued a patch but bugs will always be there  love my dual gi-275s but I wouldn’t go in the clouds without a backup source of attitude. I kept my vacuum and was lucky I did. Also used vacuum stuff is dirt cheap. 
Not worth saving 5 pounds of weight to lose a great attitude back up. 

Yeah,  I saw your comment on the previous threads about your 275 experience.  Double Garmin failure?! Jeez...

What do you think about redundant electronic AHRS system? I don't have ADSB-in, and was looking at Stratus 3, which has a built-in AHRS.

[ShuRugal]

Thank you, ShuRugal!
Looking through the records, it appears that it hasn't been changed since 2013.  I removed it and will replace. Fingers crossed that its the culprit. 

I would like to get 50-100 hrs from this plane before I will decide to start avionics conversions, although I do see the point of losing the vacuum system. 

That filter definitely needs changing. The filter media is copy-paper white when new.

That filter is so dirty I would not be surprised if it was letting unfiltered air leak past and getting dust in your gyros.

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[Mooney-Shiner]

On 12/3/2021 at 12:21 PM, AIREMATT said:

Do you have a Standby Vacuum system installed? I just removed mine with the dual G5 upgrade but had a problem after some work in my avionics compartment. The tube was knocked of the standby vac. fitting and was an easy repair once found in front of the pilot side just forward of the fire wall under the avionics access cover. The clamp was loose so it was easily bumped off.

I have all the removed parts from the Precise flight standby system in a box yet too.

I assume the low vac warning light works right? Maybe that would be the first place to look behind if it works and isn’t showing low vacuum. 
Can’t remember where in the system it’s plumbed in relative to the DG & A/I.

I looked around and it doesn't look like I have a standby system. 

Just Rapco vacuum pump, and 133A4 vacuum regulator.

 

[Rjfanjet]

Also replace the garter filter around the vacuum regulator. Mine turned to dust when I touched it. I also have a status that pairs to my iFly. Love it!

[81X]

With both vacuum instruments failing at the same time, it’s probably your pump, plumbing, and/or regulator that has failed.  In addition, your low vac light or suction probe has probably also failed, does it illuminate when your engine is off and all electronics are on? (It should). 

Relatively simple system that a good AP can fix in a jiffy. 
 

 

[Mooney-Shiner]

1 hour ago, 81X said:

With both vacuum instruments failing at the same time, it’s probably your pump, plumbing, and/or regulator that has failed.  In addition, your low vac light or suction probe has probably also failed, does it illuminate when your engine is off and all electronics are on? (It should). 

Relatively simple system that a good AP can fix in a jiffy. 
 

 

 Thank you.

The VAC  lights pass the push test with master on. They never went off. 
 

how to isolate the problem between regulator valve and the pump? Or just shot the plane with parts cannon and buy both?

[81X]

20 hours ago, ukrsindicat@yahoo.com said:

 Thank you.

The VAC  lights pass the push test with master on. They never went off. 
 

how to isolate the problem between regulator valve and the pump? Or just shot the plane with parts cannon and buy both?

A vacuum gauge would tell you this and would be needed to calibrate the vacuum regulator. You don’t need to install one per se, a good AP should have one to test with although this gear may be going out of style with the electrification of everything. 
 

Agree with the above be that the pump is usually (but not always) the culprit in this kind of situation. 

[David Lloyd]

On 12/9/2021 at 12:06 PM, ukrsindicat@yahoo.com said:

 Thank you.

The VAC  lights pass the push test with master on. They never went off. 
 

how to isolate the problem between regulator valve and the pump? Or just shot the plane with parts cannon and buy both?

The push to test just shows that the lights work.  81X asked the correct question; Does it illuminate when the engine is off and the electronics are on? It should. It is the only way to test the system in airplanes without a gauge.

[Mooney-Shiner]

57 minutes ago, David Lloyd said:

The push to test just shows that the lights work.  81X asked the correct question; Does it illuminate when the engine is off and the electronics are on? It should. It is the only way to test the system in airplanes without a gauge.

I will check, but best of my knowledge, those light only turn on whenever I push on them

[apriav]

If the budget allows go with G5s and GAD13.

So much information in front of you.

Did that on my last aircrft. Instrument flying enhanced.

And gained 13 pounds useful, weighed removed and installed.

 

[Mooney-Shiner]

18 hours ago, apriav said:

If the budget allows go with G5s and GAD13.

So much information in front of you.

Did that on my last aircrft. Instrument flying enhanced.

And gained 13 pounds useful, weighed removed and installed.

 

I'm considering it, but I'm on my first 50 hrs of the aircraft ownership and still working on my PPL.  Once I will check the PPL of my list, the panel re-do is somewhere there as well...right after the engine monitor. Unless the MOH Force majeure will pop out its ugly head.  

[Igor_U]

On 12/11/2021 at 3:02 PM, ukrsindicat@yahoo.com said:

I will check, but best of my knowledge, those light only turn on whenever I push on them

No,

By pushing the light you are testing only a light bulbs. Those are (Low and Hi) connected to Sigmatec 22-1280-04 Vacuum switch. If one is in working condition, with master on, Low light should illuminate (engine off). If not, something is wrong, switch, wiring, etc... Sigmatec switch is quite expensive... I found my broken during the pilot's panel upgrade and removed it. I have a vacuum gage...

[Mooney-Shiner]

3 hours ago, Igor_U said:

No,

By pushing the light you are testing only a light bulbs. Those are (Low and Hi) connected to Sigmatec 22-1280-04 Vacuum switch. If one is in working condition, with master on, Low light should illuminate (engine off). If not, something is wrong, switch, wiring, etc... Sigmatec switch is quite expensive... I found my broken during the pilot's panel upgrade and removed it. I have a vacuum gage...

Thank you for this heads up. The vac gauge makes better sense. Was it difficult to find the gauge?  

[Igor_U]

18 hours ago, ukrsindicat@yahoo.com said:

Thank you for this heads up. The vac gauge makes better sense. Was it difficult to find the gauge?  

I already had one installed but on copilot's panel so I just needed to move on LHS. 

There are number of Vacuum gages on the Aircraft Spruce website:

https://www.aircraftspruce.com/catalog/inpages/suctiongauges1.php?clickkey=24239

Regards,

[Mooney-Shiner]

Just to follow up.
My A&P replaced the Tempest vacuum pump and the attitude indicator is now fully functional, but the directional gyro has slight drift of 10 degrees over five minutes. We replaced the can and valve regulator filters. I connected a vacuum gauge to the inlet of DG and was steadily getting 4 inches of HG or more in vacuum.
What else should I check to stop this drift?

Below is a time-lapse video over the course of 5 minutes.

Edited February 3, 2022 by ukrsindicat@yahoo.com

[David Lloyd]

Two degrees per minute is too much.  Send the gyro for overhaul.

After your first post I should have mentioned that usually when a vacuum pump fails, it also breaks the coupling between the pump and engine.  This can be seen prior to taking anything apart.  

[StevenL757]

On 12/8/2021 at 9:02 AM, ukrsindicat@yahoo.com said:

I would like to get 50-100 hrs from this plane before I will decide to start avionics conversions, although I do see the point of losing the vacuum system. 

Personally, I wouldn't waste any more time or money on this, including aircraft downtime whilst you troubleshoot problems.

Not sure why you want to wait "50 or 100 hours" before any upgrades, but I would get this going now...especially given the long lead times for some components as well as shop lead times.  Get a reliable ADI and HSI, get a reliable backup for the ADI, get rid of the vacuum system (unless needed for vacuum-operated speed brakes, if you have them), and stop the bleeding.

[Mooney-Shiner]

13 minutes ago, David Lloyd said:

Two degrees per minute is too much.  Send the gyro for overhaul.

After your first post I should have mentioned that usually when a vacuum pump fails, it also breaks the coupling between the pump and engine.  This can be seen prior to taking anything apart.  

You are right. My old Rapco pump had a window by the shear shaft. When the pump failed, the shear shaft pieces flew through this window. When I initially saw the crumps on top of my right magnetto, I thought that I had rodents living under my cowling hahaha. Now I know...