Granville's Strut Seal - Or Other Strut Maintenance Techniques

When I stepped on the wing of my Cherokee 235 today, the strut went
completely flat. I got underneath the wing and lifted the plane back
up to a normal strut position where it stayed until I put any weight
on it; again it went completely flat. I pushed it back up one more
time and put my air gauge on it. I measured 200 psi in the strut so I
assumed the lower o-ring went bad and I needed to get a strut seal
kit. Again I put weight on the strut and it flopped right back down
to bottoming out against the landing gear.

While looking for the parts on line I came across Granvilles' Strut
Seal. I have never heard of this and am wondering if anyone has had
any experience with it. Also welcome is any other input you may have
regarding Piper main gear struts and replacement of the o-rings, or
other workarounds available to avoid needing to replace them.

When I extended the strut after collapse I did notice a small amount
of fluid on the oleo which is leading me to believe the lower end went
bad. The only thing that confuses me is how there could be such a
high air pressure in the strut if it could completely collapse.
Wouldn't the air/nitrogen escape out of the strut as well?

TIA for any responses.
z

References:
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Struts on a Piper main usually run 210 lbs. unloaded (strut fully
extended). This rises to around 550lbs at "normal" height. Yes, you
could have an upper air leak. More likely (if you have noticed seepage)
is that the main lower seals are wearing. You could have both. If you
see a small puddle, its usually the main lowers. No puddle and it may be
the upper seal washer OR the valve core itself. Don't try to use
automotive cores, they are not made for this application and pressure range.

Granville will help seeping lower seals to soften up and seal again.
Given the low cost of new seals (less than $100 for all 3 on a
Cherokee), I opted to just replace the seals. A messy 1/2 day job made
easier if the plane is up on jacks. Also, putting in Granville requires
a bit of work. Since mine were 25+ years old, that was the clincher for
replacement.

Good Luck,
Mike




zatatime wrote:
When I stepped on the wing of my Cherokee 235 today, the strut went
completely flat. I got underneath the wing and lifted the plane back
up to a normal strut position where it stayed until I put any weight
on it; again it went completely flat. I pushed it back up one more
time and put my air gauge on it. I measured 200 psi in the strut so I
assumed the lower o-ring went bad and I needed to get a strut seal
kit. Again I put weight on the strut and it flopped right back down
to bottoming out against the landing gear.

While looking for the parts on line I came across Granvilles' Strut
Seal. I have never heard of this and am wondering if anyone has had
any experience with it. Also welcome is any other input you may have
regarding Piper main gear struts and replacement of the o-rings, or
other workarounds available to avoid needing to replace them.

When I extended the strut after collapse I did notice a small amount
of fluid on the oleo which is leading me to believe the lower end went
bad. The only thing that confuses me is how there could be such a
high air pressure in the strut if it could completely collapse.
Wouldn't the air/nitrogen escape out of the strut as well?

TIA for any responses.
z

On Mon, 29 Aug 2005 22:36:52 GMT, Mike Spera
wrote:

Struts on a Piper main usually run 210 lbs. unloaded (strut fully
extended). This rises to around 550lbs at "normal" height. Yes, you
could have an upper air leak. More likely (if you have noticed seepage)
is that the main lower seals are wearing. You could have both. If you
see a small puddle, its usually the main lowers. No puddle and it may be
the upper seal washer OR the valve core itself. Don't try to use
automotive cores, they are not made for this application and pressure range.

Granville will help seeping lower seals to soften up and seal again.
Given the low cost of new seals (less than $100 for all 3 on a
Cherokee), I opted to just replace the seals. A messy 1/2 day job made
easier if the plane is up on jacks. Also, putting in Granville requires
a bit of work. Since mine were 25+ years old, that was the clincher for
replacement.

Good Luck,
Mike

Thanks for the info. Ordered a seal kit today and after reading the
manual it doesn't seem like too bad a job.

z

sounds as if the strut is out of oil
jon

When the new seals are installed, you might wish to put the recommended
amount of Granville's in with the new hydrualic fluid to fill it up. It
will help keep your new seals in better condition for longer time than
hydraulic fluid alone, and also help avoid the dreaded Piper "sticky
strut syndrome". I used to think Granville's was snake oil too, until
after seeing it work great in about a half dozen different planes.

Rumor has it that a small amount of automotive power steering fluid
sealer & treatment works just about as well as Granville's, but of
course none of us here would ever dream of putting any unapproved
substances into our certificated airplane oleo struts, lest it make the
wings fall off or cause premature impotence or something like that.


zatatime wrote:
On Mon, 29 Aug 2005 22:36:52 GMT, Mike Spera
wrote:

Struts on a Piper main usually run 210 lbs. unloaded (strut fully
extended). This rises to around 550lbs at "normal" height. Yes, you
could have an upper air leak. More likely (if you have noticed seepage)
is that the main lower seals are wearing. You could have both. If you
see a small puddle, its usually the main lowers. No puddle and it may be
the upper seal washer OR the valve core itself. Don't try to use
automotive cores, they are not made for this application and pressure range.

Granville will help seeping lower seals to soften up and seal again.
Given the low cost of new seals (less than $100 for all 3 on a
Cherokee), I opted to just replace the seals. A messy 1/2 day job made
easier if the plane is up on jacks. Also, putting in Granville requires
a bit of work. Since mine were 25+ years old, that was the clincher for
replacement.

Good Luck,
Mike

Thanks for the info. Ordered a seal kit today and after reading the
manual it doesn't seem like too bad a job.

z