What is landing gear, and how does it work on an aircraft?
Landing gear is the system that supports an aircraft on the ground and lets it taxi, take off and land safely. It usually includes the wheels, tyres, shock-absorbing struts, brakes, steering parts and retraction mechanism. In simple terms, it carries the aircraft’s weight, soaks up landing impact and keeps the aeroplane controllable on the runway.
What is landing gear on an aircraft?
On most aeroplanes, landing gear means the undercarriage: the assemblies attached to the fuselage or wings that hold the wheels. When the aircraft is in the air, fixed gear stays exposed while retractable gear folds into bays to reduce drag.
People often think of landing gear as just the wheels, but that is only part of it. The full system includes structural members, shock absorbers, brakes, steering linkages, actuators, doors on retractable types, position sensors and cockpit indications.
What does landing gear do?
- Supports weight while the aircraft is parked, taxiing, taking off and landing.
- Absorbs impact when the aircraft touches down.
- Provides braking to slow the aircraft after landing and during taxi.
- Allows steering, usually through the nose wheel or tailwheel.
- Keeps the airframe clear of the ground and maintains the correct attitude on the runway.
- Reduces drag on retractable systems by folding away in flight.
Main parts of landing gear
Wheels and tyres
These carry the load and provide the contact patch with the runway. Aircraft tyres are built for very high loads and hard landings, and they are inflated to much higher pressures than car tyres.
Struts or shock absorbers
The strut is what stops a landing from transmitting the full impact straight into the airframe. Many larger aircraft use an oleo-pneumatic strut, which combines hydraulic fluid and compressed gas. As the gear compresses on touchdown, the fluid is forced through small passages and the gas compresses, turning a hard impact into a controlled stroke.
Brakes
Most aircraft have disc brakes on the main wheels, not the nose wheel. Hydraulic pressure clamps the brake units to slow the aircraft. Larger aircraft add anti-skid systems, which do for aircraft roughly what ABS does for a car: they stop the wheels locking and help preserve tyre grip.
Steering
Tricycle-gear aircraft normally steer through the nose wheel at low speed, using pedals, a tiller or both, depending on type. Tailwheel aircraft steer from the tailwheel and rudder, often with differential braking to help turn tightly.
Retraction system
Retractable gear uses hydraulic, electric or sometimes pneumatic actuators to move the gear. The system also includes uplocks to hold the gear in the retracted position, downlocks to secure it when extended, and cockpit indications to show whether the gear is safely down.
How does landing gear work during landing?
- Approach: If the aircraft has retractable gear, the pilot selects gear down before landing. The gear extends, locks into place and the cockpit shows a safe down-and-locked indication.
- Touchdown: The main wheels contact the runway first on most fixed-wing aircraft. The tyres spin up from zero to runway speed almost instantly.
- Compression: The struts compress and absorb the vertical landing load. This protects the airframe and makes the touchdown manageable rather than violent.
- Weight transfer: As the aircraft settles fully onto the gear, more weight comes onto the wheels, which improves braking effectiveness.
- Braking and steering: The pilot uses wheel brakes, aerodynamic braking, spoilers or reverse thrust where fitted, and steers to keep straight and exit the runway.
That sequence is why landing gear has to be both strong and carefully damped. It is not just holding the aircraft up; it is managing enormous forces over a very short time.
How does retractable landing gear work?
On a retractable system, moving the gear lever sends a command to the actuator system. Hydraulic pressure or an electric motor then moves each gear leg through its travel. Once fully extended or retracted, mechanical locks or over-centre braces hold the gear in position.
The locking part matters. The system must not rely only on hydraulic pressure to keep the gear down. A proper downlock ensures the gear stays extended even if pressure is lost.
Most aircraft also have a backup method. Depending on type, that may be an emergency extension handle, manual pump, free-fall release or compressed-gas backup. The exact arrangement varies, but the goal is the same: get the gear down and locked if the normal system fails.
What are the main types of landing gear?
| Type | How it is arranged | Typical use | Key point |
|---|---|---|---|
| Tricycle | Two main wheels and a nose wheel | Most modern light aircraft and airliners | Good forward visibility and easier ground handling |
| Tailwheel | Two main wheels and a small wheel at the tail | Older designs, bush aircraft, aerobatic types | Better propeller clearance on rough strips, but trickier on the ground |
| Tandem or bicycle | Wheels aligned along the fuselage | Some military and specialist aircraft | Needs outriggers or extra support for balance |
| Fixed gear | Always exposed | Many trainers and utility aircraft | Simpler and lighter, but creates more drag |
| Retractable gear | Folds into the airframe | Faster piston aircraft, turboprops, jets | Less drag, more complexity and maintenance |
Why do some aircraft have fixed landing gear and others retract it?
Fixed gear is simpler, cheaper and easier to maintain. It also avoids a whole class of failure points, which is why it is common on training aircraft and rugged utility types.
Retractable gear cuts drag and improves speed, climb and fuel efficiency. The trade-off is added weight, cost and system complexity. On faster aircraft, the aerodynamic benefit is usually worth it.
What is the difference between main gear and nose gear?
The main gear carries most of the aircraft’s weight, especially during landing. That is why the main wheels are larger, stronger and fitted with the primary brakes.
The nose gear mainly supports the front of the aircraft on the ground and provides steering on tricycle-gear types. It is not designed to take the first touchdown in a normal landing. A nose-first arrival can damage the structure very quickly.
Common landing gear problems
- Unsafe gear indication: the gear may be down but not fully locked, or a sensor may be faulty.
- Hydraulic leaks: can affect extension, retraction or braking.
- Tyre failures: caused by wear, overheating, foreign object damage or hard landings.
- Brake fade or overheating: especially after heavy braking or rejected take-off scenarios.
- Shimmy: rapid wheel vibration, often linked to alignment, damping or tyre issues.
- Hard-landing damage: can bend components, over-stress attachments or damage wheel assemblies.
How do pilots know the landing gear is down?
Most retractable aircraft have cockpit indicator lights. The exact colours and layout vary by type, but the important point is the status: down and locked, in transit or unsafe.
Some aircraft also use warning horns or alerts if the power is reduced for landing while the gear is still up. That safeguard exists because a gear-up landing is one of the classic retractable-gear mistakes.
Landing gear in simple terms
If we strip it right back, landing gear is the aircraft’s ground-running system. It holds the aeroplane up, cushions the landing, lets the pilot steer and brake, and on many aircraft tucks away after take-off to reduce drag. It looks simple from outside, but it is one of the most heavily loaded and safety-critical systems on the aircraft.