Trouble at annual

[Red Leader]

Guys, I went by the shop to check the progress on my annual and was told that everything was great so far with two exceptions. First, my VSI is broken - it now reads climbing at 1000fpm sitting on the ground. Second is my gear - they did the gear swing and now it pops the breaker every time. To aid you in resolving my dilemma, the shop owner informed me my pitot tube was clogged with dirt-dobber stuff, which they cleaned out. I did not see this a couple of weeks ago (so it must be a recent event) and did not ask how they cleaned it. Could cleaning the Pitot tube damage the VSI? If so, could that also do something to the gear interlock system to make the breaker pop every time (It had done that previously but only two times in the last year)? They claim a thorough electrical search suggests an issue with my gear override switch - when the warning horn is disconnected from the switch, the breaker does not pop. If disconnected from the horn, it still pops (WTF?). Any ideas would be helpful. Also, I now need a 7000 C - 31 VSI, if anyone has one in good shape.

Thanks!

[Niko182]

I think i might have a vsi off a 1999 eagle. Probably not that exact model but might work.

Nik

[EricJ]

7 minutes ago, Red Leader said:

Guys, I went by the shop to check the progress on my annual and was told that everything was great so far with two exceptions. First, my VSI is broken - it now reads climbing at 1000fpm sitting on the ground. Second is my gear - they did the gear swing and now it pops the breaker every time. To aid you in resolving my dilemma, the shop owner informed me my pitot tube was clogged with dirt-dobber stuff, which they cleaned out. I did not see this a couple of weeks ago (so it must be a recent event) and did not ask how they cleaned it. Could cleaning the Pitot tube damage the VSI? If so, could that also do something to the gear interlock system to make the breaker pop every time (It had done that previously but only two times in the last year)? They claim a thorough electrical search suggests an issue with my gear override switch - when the warning horn is disconnected from the switch, the breaker does not pop. If disconnected from the horn, it still pops (WTF?). Any ideas would be helpful. Also, I now need a 7000 C - 31 VSI, if anyone has one in good shape.

Thanks!

The VSI is telling you somebody broke it.   If they blew the lines out improperly or hooked up to the wrong line that could do it, and it's definitely possible (maybe probable) that more than one instrument was damaged.   Your ASI and your altimeter may also have been affected.   A VSI doesn't just spontaneously break like that, there was probably a sudden change in pressure that caused that.   The fact that they cleaned out the pitot system suggests strongly that the events are related, imho.

It is unlikely that the gear issue is related.   If it wasn't popping the breaker before, though, it suggests that something was changed that is now causing it to do that.

[Red Leader]

4 minutes ago, Niko182 said:

I think i might have a vsi off a 1999 eagle. Probably not that exact model but might work.

Nik

Could you send me pictures of the front and back? How much do you want for it?

[Niko182]

Just now, Red Leader said:

Could you send me pictures of the front and back? How much do you want for it?

Im out of town til the 28th, but ill send you pictures when i get home.

Nik

[Red Leader]

5 minutes ago, EricJ said:

A VSI doesn't just spontaneously break like that, there was probably a sudden change in pressure that caused that.   The fact that they cleaned out the pitot system suggests strongly that the events are related, imho.

I don't know if they cleaned out the pitot system, they said the nest was in the pitot tube.

[carusoam]

Mud Dauber nests can show up in less than a day…

They can put dirt in any tube…

My friendly mud dauber filled a tank vent… blocked it completely (a decade ago…)

 

Using compressed air to clean lines attached to delicate instruments is bad…

Of course… nobody discusses putting a vacuum on the pitot system…. Which is probably equally bad… (let’s ask @EricJ)

 

There are many instruments for sale around here lately… So many G3 systems and other wide screen TVs getting installed…  

 

Best regards,

-a-

[carusoam]

Cue the discussions about pitot covers and their inherent negative aspects! 

-a-

[glenn reynolds]

The last time I had mud dabber in my pitot tube it took 125 psi to evict them.  And yes I removed the pitot tube from the plane before I run the pressure.  Vacuum can only generate 14.5 psi so I'd be skeptical that would do it.  

[1980Mooney]

17 minutes ago, Red Leader said:

Guys, I went by the shop to check the progress on my annual and was told that everything was great so far with two exceptions. First, my VSI is broken - it now reads climbing at 1000fpm sitting on the ground. Second is my gear - they did the gear swing and now it pops the breaker every time. To aid you in resolving my dilemma, the shop owner informed me my pitot tube was clogged with dirt-dobber stuff, which they cleaned out. I did not see this a couple of weeks ago (so it must be a recent event) and did not ask how they cleaned it. Could cleaning the Pitot tube damage the VSI? If so, could that also do something to the gear interlock system to make the breaker pop every time (It had done that previously but only two times in the last year)? They claim a thorough electrical search suggests an issue with my gear override switch - when the warning horn is disconnected from the switch, the breaker does not pop. If disconnected from the horn, it still pops (WTF?). Any ideas would be helpful. Also, I now need a 7000 C - 31 VSI, if anyone has one in good shape.

Thanks!

Cleaning the Pitot tube or tubing will not damage the VSI.  The VSI is on the Static Line.  For pressure to get from the Pitot line to the Static line would mean that they blew out the guts of your ASI.  It would mean that your ASI would be dead which does not seem to be the case.

The VSI may have gotten damaged separately.

Is your VSI lighted or unlighted?

 

Also

 

 

[N201MKTurbo]

The VSI often gets damaged if they are doing a static cert and somebody opens the static drain or the alternate static source while the static system is pumped down to a high altitude. It often damages the altimeter too.

Whatever trauma they inflected on the static system could have damaged the airspeed safety switch.

[EricJ]

8 minutes ago, 1980Mooney said:

Cleaning the Pitot tube or tubing will not damage the VSI.  The VSI is on the Static Line.  For pressure to get from the Pitot line to the Static line would mean that they blew out the guts of your ASI.  It would mean that your ASI would be dead which does not seem to be the case.

The VSI may have gotten damaged separately.

Is your VSI lighted or unlighted?

 

Also

 

 

What can happen is that somebody pulls the pneumatic line off the back of the ASI to blow out the pitot tube, blow it out, and then discover that the line they disconnected was the static line instead of the pitot line.   

[Guest]

8 hours ago, Red Leader said:

Guys, I went by the shop to check the progress on my annual and was told that everything was great so far with two exceptions. First, my VSI is broken - it now reads climbing at 1000fpm sitting on the ground. Second is my gear - they did the gear swing and now it pops the breaker every time. To aid you in resolving my dilemma, the shop owner informed me my pitot tube was clogged with dirt-dobber stuff, which they cleaned out. I did not see this a couple of weeks ago (so it must be a recent event) and did not ask how they cleaned it. Could cleaning the Pitot tube damage the VSI? If so, could that also do something to the gear interlock system to make the breaker pop every time (It had done that previously but only two times in the last year)? They claim a thorough electrical search suggests an issue with my gear override switch - when the warning horn is disconnected from the switch, the breaker does not pop. If disconnected from the horn, it still pops (WTF?). Any ideas would be helpful. Also, I now need a 7000 C - 31 VSI, if anyone has one in good shape.

Thanks!

Is the manual extension cover down and locked?

[Red Leader]

9 hours ago, 1980Mooney said:

Cleaning the Pitot tube or tubing will not damage the VSI.  The VSI is on the Static Line.  For pressure to get from the Pitot line to the Static line would mean that they blew out the guts of your ASI.  It would mean that your ASI would be dead which does not seem to be the case.

The VSI may have gotten damaged separately.

Is your VSI lighted or unlighted?

I have not flown the airplane since the VSI damage occurred as it is still on jacks, so there is no way for me to accurately test the ASI (that I know of), is there? My VSI is unlighted.

[Red Leader]

1 hour ago, M20Doc said:

Is the manual extension cover down and locked?

I didn't check that. Would the cover position, somehow, change the operation of the landing gear system? 

[EricJ]

48 minutes ago, Red Leader said:

I have not flown the airplane since the VSI damage occurred as it is still on jacks, so there is no way for me to accurately test the ASI (that I know of), is there? My VSI is unlighted.

The ASI is pretty easy to test with a syringe or length of plastic/rubber tubing.    You need to put a piece of tape over the drain on the back of the pitot assembly, and use a balloon or something to cover the pitot.   One way is to then connect a length of rubber (e.g., what people call "surgical" tubing), and roll it up over a pencil or something to squeeze pressure into the pitot.   Another way is to connect a syringe to add some pressure.   Your A&P/IA should be familiar with ways to do it.
 

  

[Ragsf15e]

1 hour ago, Red Leader said:

I didn't check that. Would the cover position, somehow, change the operation of the landing gear system? 

If the emergency gear extension is still engaged at all, it will affect the gear for sure.  Maybe not your problem but worth checking.

[1980Mooney]

On 8/26/2022 at 9:25 PM, Red Leader said:

Guys, I went by the shop to check the progress on my annual and was told that everything was great so far with two exceptions. First, my VSI is broken - it now reads climbing at 1000fpm sitting on the ground. Second is my gear - they did the gear swing and now it pops the breaker every time. To aid you in resolving my dilemma, the shop owner informed me my pitot tube was clogged with dirt-dobber stuff, which they cleaned out. I did not see this a couple of weeks ago (so it must be a recent event) and did not ask how they cleaned it. Could cleaning the Pitot tube damage the VSI? If so, could that also do something to the gear interlock system to make the breaker pop every time (It had done that previously but only two times in the last year)? They claim a thorough electrical search suggests an issue with my gear override switch - when the warning horn is disconnected from the switch, the breaker does not pop. If disconnected from the horn, it still pops (WTF?). Any ideas would be helpful. Also, I now need a 7000 C - 31 VSI, if anyone has one in good shape.

Thanks!

The gear interlock system is comprised of the switch with the "wheel" handle on the panel.  That switch is a solenoid.  In order for it work it needs the Airspeed Safety Switch needs to open and provide 12 V to the gear interlock system (I think the diagram calls it a Gear Safety Switch - the Service Manual calls it an Airspeed Safety Switch).  The Airspeed Safety Switch is a diaphragm switch mounted on the back of your ASI - the pitot pressure engages it at about 65 kts.  Without the Pitot pressure you need to press the Gear Over-ride Swith (see video at 55 seconds mark).  This bypasses the Airspeed Safety Switch and provides 12v to the gear interlock system.

Since your breaker does not pop when the gear swings without the gear horn connected that means there is not a problem with your gear motor or any binding in the gear.

Since it only pops when the gear horn is connected to the gear interlock, it does appear to be a short in the wire to the gear horn.  That gear horn is also connected to a micro switch on the throttle - when you pull the throttle almost all the way to idle with the gear up you hear the alarm.  However that is on a separate wire.

I think you never experienced the breaker pop because you never tried to raise the gear below 65 kts (or whatever speed your Airspeed Safety Switch is calibrated - the shop manual says +/- 5).

Lastly, if the pitot cleaning had over-pressured your ASI and destroyed the diaphragm in the Airspeed Safety Switch, the result would be that there would be no power to your Gear Interlock.  The Gear would not lower without you pressing the red Over-ride even while in the air.  But it would not cause the breaker to pop.

I think your shop is right. The diagrams below apply to your model and serial number.

But I am no expert.  However I have replaced my Airspeed Safety Switch before and have traced this out.

Also read the KNR article below.

Good luck.  

201901 Electric gear safety system (knr-inc.com)

Airspeed Safety Switch in your model and year.

 

 

 

 

 

 

 

Edited August 28, 2022 by 1980Mooney

[Red Leader]

That is a lot of information and very helpful - thanks! I don't think I made clear the exact nature of the gear malfunction. Yes, they did the swing test after cleaning my pitot tube (and somehow made my VSI read 1100fpm) but I was informed that the breaker only pops when the gear horn is disconnected from the horn end and the gear cycled. It does not pop when disconnected from the switch end. By the diagrams you provided (again, thank you!), there are other lines connected at the gear horn so it seems possible that one of those other devices may be causing the fault. If the horn line is disconnected at the switch end, my breaker might not pop but those other items will also be disconnected. I don't have the entire schematic available at this time so I don't know what the other devices might be. I am concerned the disconnection of the horn from the switch might disable or adversely affect other systems of the aircraft. Thoughts?

[A64Pilot]

Something in between the horn and the switch is grounded, easily verified by disconnecting both ends and checking for continuity from ground to the wire, if no continuity, then I’m wrong.

‘But if there is continuity disconnect whatever there is one at a time to see if you get an open. It’s possible the wire itself has chafed through and is grounded.

[Red Leader]

I recommended the same to them but was informed that this test was performed and their results were inconclusive (WTF?). The shop performing my annual has a good reputation but admittedly is not an avionics service center. This will require I take it somewhere else. Does anyone have a recommendation for shops in my area?

[A64Pilot]

A lot of very good mechanics aren’t good electricians, they won’t let you assist?

Is there an avionics shop nearby? Maybe one of them could assist?

 

[Red Leader]

As an engineer, I am confident I could resolve the issue but I have not worked on airplane avionics before and am uncomfortable on doing the work in this case. I have talked with a couple of closer shops - they are very proud of their work and it is reflected in the prices they charge (yeesh). Not to mention, they claim to be severely backed-up.

[Red Leader]

Update, I got my plane back from the shop a couple of days ago and took it for a quick flight. The replacement VSI (thanks Dominikos!) worked perfectly and there were no other indications of issues with the pitot/static instruments. My landing gear issue has been resolved and my aircraft is ready for a trip to the Mooney Summit in Tampa next week! 

[carusoam]

See you at MooneySummit!

-a-