Inflation of an oleo strut is checked by measuring the length of the exposed what?

• A. Piston rod
• B. Cylinder
• C. End cap
• D. Piston tube

Answer: (D)

An oleo strut uses compressed air to act as the spring part of the landing gear. The amount of air inside the strut (the inflation) determines how far the piston sits inside the cylinder when the leg is in a standard position. To check this, technicians measure how much of the piston tube is exposed outside the end cap in that known position. That exposed length correlates with the air charge: more exposure means less air, less exposure means more air. The measurement is then compared to the approved spec to confirm proper inflation. The other components—piston rod, cylinder, or end cap—don’t provide a straightforward, direct readout of the air charge, so they aren’t used for this check.