Static leak at alternate static air valve

[bradp]

Hi all - trying to troubleshoot a static leak.  It’s 200 fpm at the valve.  I think a majority of it is the connectors to and from - they were wrapped it about 4 decades of Teflon tape that I of course  thought was ridiculous but now that it’s gone realize was probably serving a function.  

If its not the connectors it’s the valve itself.  Anyone opened one of these up to replace the O rings?  Will be supervised by my IA etc   

Thanks 

brad. 

[Marauder]

Hi all - trying to troubleshoot a static leak.  It’s 200 fpm at the valve.  I think a majority of it is the connectors to and from - they were wrapped it about 4 decades of Teflon tape that I of course  thought was ridiculous but now that it’s gone realize was probably serving a function.  
If its not the connectors it’s the valve itself.  Anyone opened one of these up to replace the O rings?  Will be supervised by my IA etc   
Thanks 
brad. 

I have. If it is similar to the one shown, it has O rings that can be replaced. If I recall, the shaft comes out after removing a C ring on the one side.




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[bradp]

Mine is a bit different. It seems to be a square manifold with the two inputs and a big nut on the forward part (this is the presumed alternate static source).  A quick google looks like its a Gerdes A1390. 

 

[Yetti]

1 hour ago, bradp said:

Hi all - trying to troubleshoot a static leak.  It’s 200 fpm at the valve.  I think a majority of it is the connectors to and from - they were wrapped it about 4 decades of Teflon tape that I of course  thought was ridiculous but now that it’s gone realize was probably serving a function.  

If its not the connectors it’s the valve itself.  Anyone opened one of these up to replace the O rings?  Will be supervised by my IA etc   

Thanks 

brad.

Teflon tape is not how connectors work.  They are compression fittings.  Cut the tubing back and get some unmolested tubing to work with.  Or you are running new tubing. 

More than likely some new orings and maybe some silicone grease

 

[RobertGary1]

I’ve relaced the o rings in my pitot and my static drains. The pitot is a bit tough to access but it’s not a bad job. The PMA department of Home Depot sells the compression fittings you need. 

 

-Robert 

[Warren]

I agree with the previous statement that it is a compression fitting.  You should not use any teflon tape on a compression fitting as the sealing surface is at the ferrule as it is compressed on the tubing.  If you have any trouble with these fittings they are available in the Home Depot Aviation section (note:  the push in connectors work well as an alternate and are simpler for future maintenance).

Rebuilding is very simple.  Remove the large nut on the LHS  (as shown in the picture you provided).  Inside the shaft has an end with a flat screwdriver interface.  Use this flat to remove the coupler between the knob threads and the shaft threads (RHS).  There is also a small e clip on the LHS of the shaft.  Then there are three small standard size o-rings on the shaft.  They are a little difficult to remove -- mine looked like a mouse had chewed them after 30 years of service and no lubrication.  Easy to replace, add a very small amount of silicone grease and reassemble.

Good luck,

Warren

[N201MKTurbo]

You shouldn't be using the fittings from Home Depot.

You should use the Imperial Eastman or Swagelock fittings. Aircraft Spruce has them. They aren't that expensive. You can't get certs from Home Depot.

[carusoam]

Ship arriving too late to save a drowning witch...  .../\... -Frank Zappa-

Old chem eng blues...

Don’t mix and match ferels and fittings from different brands...

They suffer from the same challenge as BK and Garmin. They don’t want to be interchangeable...

So if the HD, or other brand doesn’t hold the air...

Find out what brand Mooney supplied back in the day.  The O2 system has been known to use Swagelok hardware...

A call to Lasar, might be a good idea...

I installed a dishwasher the other day using full sets of compression fittings from  HD, that was easy...  the compression fittings were a few bucks...

So getting the right ones from Lasar at 10X the HD cost... you get the right parts that will last 50years and install in minutes... protecting your static system from an error...

Consider getting the right parts to keep from getting stuck experimenting...

I would guess... re-using old ferels is the number one reason the compression fittings failed to begin with.

The ferels are maleable, and seal with a line when compressed... the line keeps them from being able to seal again...

Getting the right new parts will keep you from singing the Chem eng blues...  

Best regards,

-a-

[bradp]

Ferrules were actually in decent shape.  When I removed the old Teflon the jaggy edge of the plastic tubing was to blame.  Recut that nice and smooth and now the static system is tight again.  Thanks for the advice.  Next person who treads this way will have plenty of info. 

[Marc_B]

Updated for future searches.
 

I can’t find a drawing or parts list for the alternate static valve o-rings. So figured I’d add these for the Shaw Aero A1390 alternate static valve (M20K) and the parts for the pitot and static drains here. Highlighted o-rings are for the alt static valve. The other three are the for the drain buttons. There’s a clevis pin that gets corroded and an o-ring that can be replaced. Figured good to replace the springs for the drain as well.

[Fly Boomer]

19 minutes ago, Marc_B said:

So figured I’d add these for the Shaw Aero A1390 alternate static valve (M20K) and the parts for the pitot and static drains here.

Nice!  Great sleuthing.