Definition
A landing gear shock-absorbing strut that uses a combination of compressed air (or nitrogen) and hydraulic fluid (oil) to cushion the impact of landing and absorb taxi loads. The fluid is forced through a metered orifice as the strut compresses, dissipating energy, while the trapped gas acts as a spring that supports the aircraft's weight and returns the strut to its extended position.
Plain English
It's the part of the landing gear leg that squashes down a bit when the aircraft lands or rolls over a bump, and then springs back. Inside is oil and pressurized gas. The oil is pushed through a small hole to soak up the shock, and the gas works like a spring to hold the aircraft up.
Context Anchor
Seen during landing gear inspections, preflight checks, and maintenance discussions about how the aircraft handles landing and taxi loads.
Derivation
Oleo comes from the Latin oleum, meaning oil. The name reflects that oil is one of the two working fluids inside the strut, alongside the compressed gas.
Why Pilots Care
A properly serviced oleo strut protects the airframe from hard landing loads and gives a stable taxi. A flat or under-serviced strut can bottom out, transmit shock directly to the structure, and cause expensive damage. Pilots check strut extension during preflight to confirm it is within limits.
Analogy
It works much like a car’s shock absorber: instead of letting the wheel or gear bounce freely after a bump, it slows the motion and turns a hard jolt into controlled movement.
Intuition Check
Do not think of an oleo shock absorber as just a metal spring. It cushions by using compressed gas and oil working together.
Example Sentence 1
During preflight, the pilot checked that each oleo shock absorber was extended to the correct height marked on the strut.
Example Sentence 2
During the walk-around, the pilot checked the oleo shock absorber for correct extension and signs of fluid leakage.