If shop air was used in liu of N2 to fill the oleos, how much oleo fluctuations would be apparent with temperature changes? If it was filled normal in summer, would 3/4" low be possible in single digit F temps? All 3 of my oleos are downabout the same amount and trying to figure why.... The airplane was flying last week at 5F. Prior to that it would have been about 25F as the coldest since summer.

Thanks,

I noticed that when the temperature went from 80 to 70, my strut was down abut 1/8". It went back up when it got warm again. I have N2 in them though so even with N2 there is a bit of variation.

Using air in your strut will make no difference on a small piston airplane that operates below 18000. The main purpose of nitrogen is the purity and lack of moisture for an aircraft that operates in the flight levels at some extremely cold and greatly varying temperatures.
As to temperature fluctuations on strut height... yes, summer to winter can have a reasonable affect. Adjust in both seasons to be sure... just as with tires.. as soon as the temperature changes dramatically be sire to check tire pressures.

thanks! I did do the tires, but did not consider the struts till now it's obvious. (1st time "strut" owner. Never a concern with the bungee gear!

If I take the weight off, would 100 psi be high enough to service the struts?

DO NOT try to use shop air to fill your struts!

Shop air:

https://youtu.be/AwSzMNxWb1o

Thanks,

Point taken. I do have a drier/water drain system on the compressor.

What if the shop air had 5606 in it? Wouldn't that save a few steps??

Now you are showing what you don't know!
If you don't have a service manual and understand the filling procedure for your strutthen I would recommend getting some help or learning... I don't know what airplane you have but typically you must...
1 get strut off ground
2 confirm the level of hydraulic flyid is correct for proper operation
3 inflate strut usually with it fully compressed first
Some aircraft you fill hydraulic fluid while compressed and then add air/nitrogen

So, 100psi may be enough for most cessna struts but not for others

Thanks,

I do have a maunual, and the correct proceedure. The manual does call for shop air. What it does not specify is what psi out put is needed. Since it doesn't specify, and they do call for shop air I presume that the typical 100-150psi will be sufficent to service iaw the shop manual. All I wanted to know is does that sound right. I had always thought that N2 was the only gas used due to the lack of mioisture and the high psi delivery possible.

Is there a helpful answer or .......

100 psi isn't enough for many struts, the manual referencing compressed air might be assuming you are using a strut pump which will multiply your inlet pressure many times.

100 may not quite make it on a main gear strut depending on gross weight... likely 150 will.. most cessna nose struts only take 55-80 psi.
So does the manual say just extend to "x" inches?
I would also advise buying a shrader screw on type adapter.. you cant really just blow some air in very easy with a conventional air adapter... you need to apply a lower pressure and then increase the regulator to bring it up to the value you desire. It really isnt difficult... just go play with it.

Thanks,

yes, the shop manual instructs extending to 2.75". I may have the shop do it this time, and get myself setup for the subsequent times. I din't realize tha it will be a season requirement. I'll see what I can do before I need the airplane again.

Thanks again,

FWIW, shop air is 80% nitrogen. I'm not a physicist but I doubt there is much, if any, difference between the thermal expansion of shop air and pure nitrogen. If one is serious about participating in maintenance and the shop manual specifies nitrogen, a small nitrogen bottle with valves and hoses is not a large expense aviation-wise. There's been a couple threads on BT on how to set one up.

Again, there's absolutely no difference in the expansion of N2, air, O2, or any other gas with the same temperature variation as long as there's no phase change. The fact that shop air often has a much higher water content than N2 from tank, does mean that there will be a greater pressure change vs temperature with the water laden air (water, unlike N2 does go through phase change in the temperature range our airplanes see), however another fact is that even with shop air, the water content is so low that this effect is pretty insignificant.