Static Leak Troubleshooting

[bob865]

Hey guys,

I've got my plane in the shop installing a G5 to replace my lazy ADI.  During the install they found a leak in my static system of over 1000' per minute.  To get my static system to pass the 100'/min tolerance they are still working but we are already at 18hrs.  They have basically replaced all the fitting in the system and are about to replace the alt static source valve and the spring in the drain valve.  Does anyone have any experience troubleshooting a static leak?  Looking for some guidance as to if this sounds reasonable or not?  It's my first time using this shop and I'm not feeling good about what is going on.  I did a search before asking, but I didn't see any results that answered my question.

Thanks!

[takair]

The drain would be the first thing to look at.  They get FOD and don’t seal.  Next, be sure the instruments are not at fault.  Leaky glass on VSI.  Check the baro knob on the altimeter. Check the encoder fittings.  Instruments can also leak internally and need to be isolated.  From there it is a matter of isolating the system to narrow in on the offending line or fitting.

[bob865]

At one point they had told me the VSI was the leak.  They then pull the VSI out and find it's the connections in the back.  Those fittings are replaced.  Leak persists, but is better.  Now it's the spring int he drain valve isn't adequate to keep the seal and the alt static valve under the panel isn't sealing.  Normally I would have been at the tech's side as soon as he said he had a leak, but I got stuck in Detroit for the week when she went into the shop.

[Marauder]

Hey guys, I've got my plane in the shop installing a G5 to replace my lazy ADI.  During the install they found a leak in my static system of over 1000' per minute.  To get my static system to pass the 100'/min tolerance they are still working but we are already at 18hrs.  They have basically replaced all the fitting in the system and are about to replace the alt static source valve and the spring in the drain valve.  Does anyone have any experience troubleshooting a static leak?  Looking for some guidance as to if this sounds reasonable or not?  It's my first time using this shop and I'm not feeling good about what is going on.  I did a search before asking, but I didn't see any results that answered my question.

Thanks!

 

 

 

Static port is usually the leak point. The seat gets rusty and can be ground smooth and a new O ring installed. If it gets too corroded, you can replace it. Lasar sold me this one for $127. Came from Mooney.

 

 

The second most likely place for the leak is the alternate static port. Mine was found leaking 2 or 3 times in the 27 years I have owned my Mooney.

 

The third place is an actual split or hole in the tubing itself. Since this tube runs along the interior of the plane, if you had any interior work done, a misplaced screw could have punctured it or the tube split because of age.

 

 

Sent from my iPad using Tapatalk Pro

 

[bradp]

The drain is the first, second and third thing to look at.  Alternate static valve is another common point of failure. 

The way to approach this is to divide and conquer.  It's dead nuts simple and shouldn't take 18 hours.   It takes half a brain (I can do it), some organization, and some equipment.   It's akin to a choose-your-own-adventure book.  

Usually there's a T-piece or junction in the empennage for the plastic line (that's where they do my leak test from) that you can gain access to.  Tape over your static ports (be very cognizant that you need to untape them before flight) pull a slight vacuum on the AFT side of the access point.  This measurement point should be "before" the insertion of the drain.  Then do the FORWARD side.  If you have a leak in drain / tubing / connections / instruments you should see it in the FORWARD measurement, if it's the static port or T union the leak should be in the AFT measurement.   

Note:  the brass connectors at the drain or ports can be the issue and not just the spring drain.  I've fixed my drain in a stuck open position by shooting it with a lot of triflow / your favorite lubricant.  Search the forum for static drain.  There are a couple of similar threads. 

Next close up the access port in the tail, and take your measurement apparatus (if done by your avionics shop they can use their testing setup, if you DIY it you can use an old altimeter or vacuum gauge, a medical syringe, three way stopcock and medical tubing sealed to 1/4" static tubing) FORWARD in the cabin to the next place you can access the system.  There should be a junction in the panel before it splits at your instruments.   Now measure everything AFT for a leak - if it's an instrument or a connector in the panel you shouldn't see a leak AFT.   Now measure FORWARD - If it's a connector to the G5 or your other static instruments, you should see a leak.  Keep dividing and conquering in this way until you find the exact location of the leak.  Just make sure you are measuring a "closed" system.  You could test every potential place for a leak in the system in about an hour using this method. 

Word of caution: always go SLOWLY and draw and release vacuums connected to instruments is a regulated way.  Don't drop them by more than about 1000 fpm to avoid damage to instruments. 

Note: I did my own G5 install and made sure that I had a good tight static system before I brought it to a super expensive avionics shop for a static leak down test.   I did have a static leak which I fixed- I had nylo-seal connectors and one of them didn't have the little plastic ID insert that creates the "lock".  This was at a T connector behind the panel.  Added the little 5-cent connector and all was good to go.  Make sure that they used compatible tubing and connectors for the install.  

 

 

[Mooneymite]

18 Hours!  I hope this includes the install, not just looking for the leak.

If your static system uses the plastic lines, they can be very sneaky.  A hairline crack will not show up until a little pressure is applied...and this has to be done with the proper precautions in place!

Since the shop is suggesting a 1000'/min leak and you probably didn't have anything like this when you last flew your plane, I'm suspecting it is a split in a plastic fitting, or line somewhere which only shows this magnitude of leak while being tested.

Keep us posted.

[bob865]

18 hours ago, Mooneymite said:

Since the shop is suggesting a 1000'/min leak and you probably didn't have anything like this when you last flew your plane

That's my concern.  When I flew last, I saw no problems with any instruments.  The system was also certified by a different shop about a year ago (if memory serves).  I'm sure they did find a leak.  It's a 40+ year old plane and stuff breaks.  I'm just not sure how much was failed equipment vs. them doing the work correctly or damaging something. I'm just baffled that after 2 days of troubleshooting, they are just now finding the alt static port and the drain valve.  As I understand, they found 3 leaks, 1) Drain valve, 2) alt static source, 3) Connections at the back of the VSI.

I had a G5 promised to me by another shop, but when I showed up to get it installed they told me that they didn't have any.  They were just too hard to get from Garmin.  My partner called and he fessed up to selling the unit promised to us to someone else.  So I had to go back to the drawing board.  These guys were new on the field, so I decided to give them a go.  Try them out before I get to my ADS-B upgrades.  Not looking like I am going to use them again.  I guess I know why my second choice shop has a backlog out until May.