Parts of a Landing Gear – Labeled Diagram and Quiz

All 15 parts on the diagram

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The gear from the side 11

Shock strut (oleo strut) It takes the shock of landing with air and oil. They are inside two tubes that slide one in the other. It is also called an oleo strut or air-oil strut.
Trunnion It is part of, or fixed to, the upper cylinder. Its bearing surfaces let the whole gear swing up when it retracts.
Torque links They keep the piston from turning, so the wheel stays pointing straight. They are also called torque arms or scissors.
Drag brace It holds the leg firm for landing and on the ground. It has a hinge near the middle and folds when the gear retracts. It is also called a drag strut.
Actuating cylinder Fluid under pressure moves its piston rod in or out. That swings the gear up or down.
Gear door It closes over the wheel well once the gear is up. Then the skin is smooth in flight.
Wheel well A retracted gear is stowed here, out of the airflow.
Tire It and the strut together smooth out bumps while the airplane taxis.
Wheel It turns on the axle.
Brake assembly It grips the turning wheel to slow and stop it.
Axle It is fixed to the foot of the piston. Here you see its end.

The shock strut cut open 4

Outer cylinder It is fixed to the aircraft and does not move. Air, or nitrogen, fills the top of it, above the oil.
Piston It is the lower cylinder, and it carries the axle. Landing pushes it up.
Orifice Landing forces oil up through it. Squeezing oil through a small hole is what soaks up the shock.
Metering pin It sets how fast the oil can flow. Its taper changes how much room the oil has as the piston rises.

How this list was compiled: Part names checked on 2026-09-30; a name is kept only when two independent sources use it. (1) FAA, Aviation Maintenance Technician Handbook - Airframe, volume 2 (FAA-H-8083-31A), chapter 13, Aircraft Landing Gear Systems, https://www.faa.gov/sites/faa.gov/files/2022-06/amt_airframe_hb_vol_2.pdf (shock strut of two telescoping cylinders, outer cylinder, inner cylinder called the piston, orifice, tapered metering pin, torque links or torque arms, trunnion, drag brace and drag strut, side brace, actuating cylinder, landing gear doors, wheel wells, axle, wheels, tires, brake assembly). (2) US Navy rate training manuals, Aviation Structural Mechanic H 1 & C, https://archive.org/details/micro_IA41153035_0584 , and Aviation Structural Mechanic S 3 & 2, https://archive.org/details/micro_IA41153123_0694 (shock strut, outer and inner cylinders, torque links and torque arms, trunnion, drag brace, side brace and side struts, actuating cylinder, landing gear doors, wheel well, axle, brake assembly, metering pin and orifice). (3) Wikipedia, text only: Landing gear, https://en.wikipedia.org/wiki/Landing_gear (retractable gear stowed in a wheel well, torque links, axle, wheels, tires); Oleo strut, https://en.wikipedia.org/wiki/Oleo_strut (inner tube or piston attached to the wheel axle, outer cylinder, oil forced through orifices, scissor or torque links). Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; no maker's gear, nothing traced. Licence: own work

How it works

The parts of a landing gear carry an airplane on the ground and take the shock when it lands. This one is a main gear that folds up into the wing.

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The gear from the side

The leg is the shock strut. It swings on the trunnion at its top, inside the wheel well. The drag brace holds it firm and the actuating cylinder pulls it up. The gear door closes over the well. The torque links keep the wheel straight. At the foot are the axle, the wheel, the tire and the brake assembly.

The shock strut cut open

The piston slides up into the outer cylinder. Landing forces oil through the orifice, past the tapered metering pin, and squeezes the air at the top.

Both handbooks also name a side brace. It steadies the leg sideways, so it does not show in a side view.
A fixed gear has no wheel well, gear door or actuating cylinder.

Questions and answers

What are the parts of a landing gear?

A shock strut that pivots on a trunnion, torque links, a drag brace or side brace, an axle, a wheel, a tire and a brake assembly. A retractable gear adds an actuating cylinder, gear doors and a wheel well to fold into.

What is an oleo strut?

A shock strut that works with air and oil. A piston slides inside an outer cylinder. On landing the piston is pushed up and oil is forced through a small orifice, which turns the shock of landing into heat.

What do torque links do on a landing gear?

They join the fixed upper cylinder to the piston so the piston cannot rotate, which keeps the wheel aligned. They also hold the piston in the cylinder when the strut is fully extended.

What is a trunnion on a landing gear?

The pivot at the top of the leg. It is part of, or fixed to, the upper strut cylinder, and its bearing surfaces let the whole gear move when it retracts.