Deflated Strut

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DakotaSM

Filing Flight Plan
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Jan 6, 2018
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DakotaSM
Hey Ya'll. I fly a P28-236 (piper dakota) with a right main strut that keeps deflating after 1 to 2 weeks. I'm out of ideas and wondered if anyone has had this issue with their piper.
Strut has been serviced multiple times
seals have been replaced along with a new chrome strut.
Tried two different shops with the same outcome.
No obvious fluid leakage.
Loosing nitrogen pressure in strut.

If you have any ideas, feel free to post. Even if its an important step in the rebuild process that should not be overlooked, I would love the help. I am currently mystified by this issue.
 
Deflate the strut, pop the cover off the wing and remove the valve body from the strut. There is a small aluminum gasket that seals the valve body to the strut and it tends to be overlooked (gets corroded over time). Scotchbrite the sealing surfaces and replace the gasket. Might also want to replace the schrader valve as well. Service with nitrogen.
 
Are these the same oleo struts as "smaller" PA28s? They are notorious for leaking, although I've never seen them leak as quickly as you noted. Every Warrior I've flown had problems with them at one time or another and had to have the seals replaced.
 
remember they do have a high pressure schrader valve
 
Yes, the dakota shares its struts with many of the smaller pipers(one exception is the rarer turbo dakota which has a different nose wheel/strut). Great suggestions everyone. I was also thinking of adding Granvilles strut seal when it is serviced. Does anyone have any experience with this. I know it probably won't make a difference with the nitrogen leak up top but I figure its cheap insurance for the lower seals especially with the cold weather we have been having in ohio. I know it may be placebo but my main concerns are any negative effects it may have on the airplane. Has anyone had any negative experiences with the product?
 
Also, What pressure does the compressor need to achieve in order to use shop air. We have always used nitrogen from a bottle but with how much hassle this has caused it may be easier to keep a compressor in the back of the hanger and just shoot the strut before the flights. I know when its jacked up it requires 250psi. Not sure if anyone knows the general it requires to inflate it on the ground. Thanks!
 
Is the strut low on fluid? If not, you will have to suck some fluid out from the top or dismantle it and start over with new seals.
Trying to add granville to a fully serviced strut is a wasted effort - can't fill a full cup any more.
 
If you use shop air you'll need a "strut pump" to get the pressure high enough. The reason nitrogen is often used is that it's the easiest of the compressed gasses to use (the bottles are up over 2000psi to begin with typically). It's reasonably inert for this application. Nobody sells compressed "air" in bottles except for scuba or fire service applications. Neither CO2 or O2 is inert enough. Helium has a problem with diffusion through the rubber seals, so Nitrogen is the goto gas.
 
DakotaSM said:
Hey Ya'll. I fly a P28-236 (piper dakota) with a right main strut that keeps deflating after 1 to 2 weeks. I'm out of ideas and wondered if anyone has had this issue with their piper.
Strut has been serviced multiple times
seals have been replaced along with a new chrome strut.
Tried two different shops with the same outcome.
No obvious fluid leakage.
Loosing nitrogen pressure in strut.

If you have any ideas, feel free to post. Even if its an important step in the rebuild process that should not be overlooked, I would love the help. I am currently mystified by this issue.
Click to expand...

inspection of the casting for a crack is called for. the piper castings have a history of cracking around the scissor mount lugs, if a crack goes into the bore the nitrogen charge will leak out. clean the strut and start with at least a 10x glass.
bob
 
That's one on me, didn't realize Piper's had such a high pressure strut.
 
Automotive transmission stop leak, plugs most leaks.
 
Paulie said:
That's one on me, didn't realize Piper's had such a high pressure strut.
Click to expand...

It's between 200-300 psi. Not as high as most gas bottles, but more than most shop compressors can handle.
 
fill it up.....spray it down with soapy water.....look for bubbles. Try this with the wheels on the ground....then rinse and repeat with it on jacks. You may have leaks with it extended.
 
flyingron said:
If you use shop air you'll need a "strut pump" to get the pressure high enough. The reason nitrogen is often used is that it's the easiest of the compressed gasses to use (the bottles are up over 2000psi to begin with typically). It's reasonably inert for this application. Nobody sells compressed "air" in bottles except for scuba or fire service applications. Neither CO2 or O2 is inert enough. Helium has a problem with diffusion through the rubber seals, so Nitrogen is the goto gas.
Click to expand...

Nitrogen has no moisture in it to corrode the strut internally. Using oxygen against oil would be insanely suicidal, especially at any pressure.
 
Checkout_my_Six said:
fill it up.....spray it down with soapy water.....look for bubbles. Try this with the wheels on the ground....then rinse and repeat with it on jacks. You may have leaks with it extended.
Click to expand...
If it takes 2 weeks to leak down you won't see any bubbles with soap.
 
I have a strut pump which uses shop Air of 125psi to deliver up to 400psi in bursts. Easy enough, but nitrogen is preferable if available.


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Okay, I’ve had enough. My strut is not deflated and no nitrogen is not required for inflation. That is all.
 
Clark1961 said:
Okay, I’ve had enough. My strut is not deflated and no nitrogen is not required for inflation. That is all.
Click to expand...

Um, ok. Good to know. I stayed at a Marriott last week! ;)
 
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