Cessna Struts

[jls]

These are the most wonderfully engineered oleo struts in the world. They
are easy to rebuild and easy to service.

Filling one with 5606 hydraulic fluid, however, is not best done by the
book. You slip a tube which fits tightly over the schrader (with the stem
removed) and the other end of the tube into your can of red hydraulic fluid.
Then you pull out the collapsed strut to its full extension, thereby sucking
5606 fluid into the hollow strut. Extend and collapse the strut several
times until you have filled it so no more air comes out of the strut, only
red fluid. Make sure the strut is collapsed and yet full to the brim with
5606. Then you put the stem back in, screw it down for a good seal, and
pump dry nitrogen through the schrader until the airplane's nose comes up to
the desired level. If you pump it up too high, you'll overstress the strut
and you CAN break it with a hard landing, or in sod because of the long arm.
Nitrogen, an inert gas, keeps the inside of the strut from corroding.

[RST Engineering]

I don't understand what advantage this has over simply deflating the strut,
removing the schrader fitting, filling it to the brim with 5606, replacing
the schrader, and pumping it with a gas (air or nitrogen). You can argue
for nitrogen if you want, but the sloshing of the 5606 inside that strut
keeps it pretty well oiled for plain old air. Besides, nitrogen comes out
the spigot at a pretty good pressure, and you can adjust an air compressor
down to where it won't blow the piston out the bottom of the strut.

Jim


" jls" > wrote in message
.. .
> These are the most wonderfully engineered oleo struts in the world. They
> are easy to rebuild and easy to service.
>
> Filling one with 5606 hydraulic fluid, however, is not best done by the
> book. You slip a tube which fits tightly over the schrader (with the
> stem
> removed) and the other end of the tube into your can of red hydraulic
> fluid.
> Then you pull out the collapsed strut to its full extension, thereby
> sucking
> 5606 fluid into the hollow strut.

[jls]

"RST Engineering" > wrote in message
...
> I don't understand what advantage this has over simply deflating the
strut,
> removing the schrader fitting, filling it to the brim with 5606

That will work just fine if you can get the fluid to it, way back there on
the firewall behind the mags and alternator and all those wires, without
making a mess.

, replacing
> the schrader, and pumping it with a gas (air or nitrogen). You can argue
> for nitrogen if you want, but the sloshing of the 5606 inside that strut
> keeps it pretty well oiled for plain old air.


OK.



Besides, nitrogen comes out
> the spigot at a pretty good pressure, and you can adjust an air compressor
> down to where it won't blow the piston out the bottom of the strut.

We use nitrogen by adjusting the pressure with a relief valve upstream of
the schrader before inflating the strut. Nitrogen is cheap and so is the
relief valve. A nitrogen bottle without a relief valve could be dangerous,
or I guess even more dangerous than it already is because of the high
pressure.

Have a good cross-country, now, heah?
>
> Jim
>
>
> " jls" > wrote in message
> .. .
> > These are the most wonderfully engineered oleo struts in the world.
They
> > are easy to rebuild and easy to service.
> >
> > Filling one with 5606 hydraulic fluid, however, is not best done by the
> > book. You slip a tube which fits tightly over the schrader (with the
> > stem
> > removed) and the other end of the tube into your can of red hydraulic
> > fluid.
> > Then you pull out the collapsed strut to its full extension, thereby
> > sucking
> > 5606 fluid into the hollow strut.
>
>

[Don Hammer]

>I don't understand what advantage this has over simply deflating the strut,
>removing the schrader fitting, filling it to the brim with 5606, replacing
>the schrader, and pumping it with a gas (air or nitrogen). You can argue
>for nitrogen if you want, but the sloshing of the 5606 inside that strut
>keeps it pretty well oiled for plain old air. Besides, nitrogen comes out
>the spigot at a pretty good pressure, and you can adjust an air compressor
>down to where it won't blow the piston out the bottom of the strut.
>
>Jim
>

We can all invent our own way of maintaining an airplane, but the
approved proceedures and materials, what ever they are, are in the
airframe maintenance manual. I don't know how Cessna built these, but
some struts have metering pins or other devices that won't allow them
to be completely filled unless they are extended first. Do what the
manufacuter says and you won't get in to trouble.

Ever seen water come out of your air compressor? Ever seen an aluminum
strut tube corrode from water mixed with the fluid? I've seen both.
Nitrogen is cheaper than struts. Why bother changing engine oil if
the airplane's been setting for six months? Lots of oil sloshing
around in there.

Why don't you just recommend commercial hydraulic fluid? It's cheap
and you can get it everywhere. Works fine in tractors so it must be
OK in an airplane!!

[RST Engineering]

"Don Hammer" > wrote in message
news:1121355676.d3689304ec05d387a512c3739194101f@t eranews...
>
> We can all invent our own way of maintaining an airplane, but the
> approved proceedures and materials, what ever they are, are in the
> airframe maintenance manual. I don't know how Cessna built these, but
> some struts have metering pins or other devices that won't allow them
> to be completely filled unless they are extended first. Do what the
> manufacuter says and you won't get in to trouble.

See Cessna Service Manual section 2-18. Don't you think Clyde's boys know
what they are talking about when they write a manual? Don't post out of
ignorance.


>
> Ever seen water come out of your air compressor? Ever seen an aluminum
> strut tube corrode from water mixed with the fluid? I've seen both.
> Nitrogen is cheaper than struts. Why bother changing engine oil if
> the airplane's been setting for six months? Lots of oil sloshing
> around in there.

Ever seen an A&P's shop that doesn't have a water trap on the compressed
air?

>
> Why don't you just recommend commercial hydraulic fluid? It's cheap
> and you can get it everywhere. Works fine in tractors so it must be
> OK in an airplane!!

Damned fool.

Jim
A&P/IA

[Don Hammer]

>
>See Cessna Service Manual section 2-18. Don't you think Clyde's boys know
>what they are talking about when they write a manual? Don't post out of
>ignorance.
>
>
Don't have the manual. Guess it says to use compressed air and not
nitrogen huh?

My point is I see lots of posts from "experts" here that lead people
down a not-so-good path. What I said stands - Do what is in the
maintenance manual and you can't go wrong. Am I not correct?

[RST Engineering]

Out of the 100-series service manual.

I'll do this in some abbrvtd method (I don't type more than I have to):

quote on

1. Remove valve cap and release all **AIR** (emphasis mine)
2. Remove valve housing
3. Compress strut completely
4. Fill strut with hydraulic fluid to valve hole
5. Get nose wheel off the ground
6. Replace valve housing and inflate: 35 psi (or 20 psi on the 150 and 50
psi on the 182 both models after the 1961 model year)

<quote off>

Note they said to release AIR and not nitrogen. They don't specify WHAT to
inflate with, so it is left to the A&P to determine the correct gas.
However, you might infer from the first instruction that they expect air.

Jim



"Don Hammer" > wrote in message
news:1121375152.eb841dd4e866bfcb751910a2ac0e0572@t eranews...
>>
>>
> Don't have the manual. Guess it says to use compressed air and not
> nitrogen huh?

[[email protected]]

On Thu, 14 Jul 2005 14:43:17 -0700, "RST Engineering"
> wrote:

>Out of the 100-series service manual.
>
>I'll do this in some abbrvtd method (I don't type more than I have to):
>
>quote on
>
>1. Remove valve cap and release all **AIR** (emphasis mine)
>2. Remove valve housing
>3. Compress strut completely
>4. Fill strut with hydraulic fluid to valve hole
>5. Get nose wheel off the ground
>6. Replace valve housing and inflate: 35 psi (or 20 psi on the 150 and 50
>psi on the 182 both models after the 1961 model year)
>
><quote off>
>
>Note they said to release AIR and not nitrogen. They don't specify WHAT to
>inflate with, so it is left to the A&P to determine the correct gas.
>However, you might infer from the first instruction that they expect air.
>
>Jim
>
And "air " is what percentage nitrogen? Something like 78% nitrogen
and 21% oxygen.
That oxygen WILL slowly react with the oil in the strut, with any
rubber parts, and with the metal parts, particularly if the air is
moist. Granted, these reactions WILL stop over time, as the oxygen
gets depleted.
Nitrogen fill has NONE of these drawbacks, and NO downside over using
"air".

The advantages of "Nitrogen Fill" for tires have been debated for
decades, but the current informed opinion is that there are
significant benefits, and "aging" related deterioration of the tire is
markedly reduced.
Almost all good automotive and industrial "shock absorber"
applications use pressurized nitrogen fill - there is NO REASON not to
use nitrogen in place of air in an aircraft supension strut - and
several pretty convincing arguements for doing so.


>
>"Don Hammer" > wrote in message
>news:1121375152.eb841dd4e866bfcb751910a2ac0e0572@t eranews...
>>>
>>>
>> Don't have the manual. Guess it says to use compressed air and not
>> nitrogen huh?
>