The landing gear on an aircraft serves as its foundation when not airborne, playing a fundamental role in ground operations. This system supports the entire weight of the aircraft, enabling it to move safely on the ground, take off, and land without sustaining damage. Beyond simply holding the aircraft up, the landing gear is engineered to absorb significant forces and provide stability during all phases of ground movement. Its design ensures the aircraft can transition smoothly between flight and ground.
Primary Locations on an Aircraft
The placement of landing gear on an aircraft is strategic, designed to provide optimal stability and maneuverability during ground operations. The most common arrangement is the tricycle landing gear, which features two main gear assemblies positioned under the wings or fuselage, and a single, smaller wheel at the front, known as the nose landing gear. This configuration ensures stability by keeping the aircraft level while on the ground and allows for better forward visibility for the pilot during taxiing, takeoff, and landing.
Another configuration, found on older or smaller aircraft, is the conventional landing gear, also called a “taildragger.” This setup has two main wheels located forward of the aircraft’s center of gravity, with a smaller wheel or skid at the rear of the fuselage. While providing good ground clearance for large propellers and suitability for unimproved fields, tailwheel aircraft are more challenging to control directionally on the ground than tricycle gear. Some specialized aircraft might also feature tandem or multi-bogie landing gear, where wheels are aligned along the fuselage centerline, or multiple units to distribute heavy loads.
Key Components and Their Functions
The landing gear system comprises several specialized components, each performing a specific function for safe ground handling. The wheels, fitted with durable tires, bear the aircraft’s weight and provide traction on the runway. Aircraft tires are designed to withstand heavy loads and high pressures, often inflated with nitrogen to minimize expansion and contraction due to temperature changes. They also feature tread patterns to prevent hydroplaning and aid braking.
Attached to the wheels are the struts, which act as the aircraft’s shock absorbers. The oleo-pneumatic strut, a common type, uses hydraulic fluid and compressed gas to cushion landing impact and dampen oscillations during taxiing. This system protects the airframe from stress. Brakes, typically disc brakes, are integrated into the wheels to slow and stop the aircraft. These brakes reduce stopping distance and are often coupled with anti-skid systems to prevent wheel lock-up.
Steering mechanisms allow aircraft to be controlled on the ground. For aircraft with nose landing gear, steering is commonly achieved through a nose wheel steering system, operated by a tiller or rudder pedals. This system enables precise turns during taxiing. In some cases, differential braking—applying brakes independently—can also be used for steering. The rudder, primarily an aerodynamic control surface for flight, also assists with directional control at higher ground speeds.
Its Essential Role in Flight
The landing gear’s purpose extends beyond static support for a parked aircraft. It provides the foundation for all ground operations, including taxiing, accelerating during takeoff, and decelerating upon landing. During takeoff, the landing gear supports the aircraft’s weight as it gains speed, ensuring a smooth ground roll before lifting off. Without this stable platform, the aircraft could not achieve the required velocity for flight.
Upon landing, the landing gear absorbs impact forces when the aircraft touches down. The shock-absorbing components dissipate energy, preventing structural damage to the airframe. This ability to absorb and distribute loads is important for the aircraft’s structural integrity and operational safety. The landing gear also facilitates braking and steering on the ground, allowing the aircraft to navigate runways and taxiways safely after landing.
How It Operates
The extension and retraction of modern aircraft landing gear are typically managed through hydraulic or electric systems. In hydraulic systems, pressurized fluid is directed to actuators, which push or pull the landing gear into position. Hydraulic power is often favored for larger aircraft due to its ability to generate high forces needed to move heavy gear assemblies.
Electric systems use electric motors and mechanical linkages to extend and retract the gear. These systems can offer advantages like reduced maintenance and lower weight compared to hydraulic counterparts. Once the landing gear is fully extended or retracted, mechanical locks engage to secure it, preventing inadvertent movement during flight or ground operations. Pilots receive indicator lights confirming its position (up, down, or intermediate).