Cessna Struts

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.