Landing gear

Planes use gear to touch the ground.

This gear holds the plane's weight. It keeps the body safe from the ground. Most planes use wheels for this. Some planes use floats to land on water. Many modern planes fold their wheels up. This helps them fly faster and smoother.

The gear must be very strong. It takes a big hit when landing. This keeps the flight safe for everyone.

Landing gear is the part of an aircraft that touches the ground.

It holds the weight of the plane while it is not flying. This keeps the body of the plane safe from the ground.

Most planes use wheels. Some planes use skids or floats to land on snow or water. Many modern planes have retractable gear. This means the wheels fold up into the plane during flight. This helps the plane fly faster and smoother.

There are different ways to set up the wheels. A tricycle layout has three sets of wheels. A taildragger has two main wheels in front and one small wheel in the back. Some planes use a bicycle layout with wheels in a line.

Landing gear must be very strong. It must handle the weight of the plane. It also must take the shock of touching the ground. Large planes use many wheels to spread out their weight. This helps keep the runways safe.

Landing gear is the essential part of an aircraft that touches the ground.

It supports the whole weight of the craft when it is not flying. This keeps the fuselage, or the main body, high above the ground. High clearance helps the plane avoid damage from hitting the surface. Most planes use wheels to move on land. Some planes use skids for snow or floats to land on water.

How the gear works depends on the type of plane. Early aircraft used fixed gear that stayed out during flight. This creates drag, which is air resistance that slows a plane down. Most modern planes use retractable gear to fly faster. The wheels fold into a compartment called a wheel well.

This makes the plane more streamlined for smooth flight. Many systems use hydraulics, which is liquid power, to move the gear. Pilots check if the gear is locked by looking for "three greens" on their lights.

Engineers have designed many different wheel layouts over time. A tricycle layout has three sets of wheels, with one in the nose. A "taildragger" has two main wheels in front and a small wheel at the back. This was common during the early propeller era to give the propeller more space.

Some special planes use a bicycle layout with wheels in a line. The Lockheed U-2 spy plane is one example of this. Other planes use a quadricycle layout with four sets of wheels.

History shows how gear changed as planes grew larger. The Zeppelin-Staaken R.VI was a German bomber from 1916. It used eighteen wheels to support its huge weight. During World War II, the Arado Ar 232 used eleven sets of twin wheels.

Modern giants like the Boeing 747 use many wheels to stay safe. The 747 has four main landing gear posts and 16 wheels. This helps spread the weight so the heavy plane does not break the runway.

Landing gear is a very important part of flight safety. It makes up about 2.5 to 5% of a plane's takeoff weight. It also costs about 1.5 to 1.75% of the total price of the aircraft. However, maintenance for the gear is a big job. It can cost 20% of the direct maintenance for the whole airframe.

Strong shock absorbers, like air and oil struts, help handle the impact. This ensures the plane stays safe during a touchdown.

Landing gear is the essential undercarriage of an aircraft or spacecraft. It is the foundational part of the airframe that supports the vehicle's weight when it is not in flight. This system keeps the fuselage, or the main body, at a safe clearance from the ground. This distance prevents the aircraft from sustaining frictional or collisional damage during ground operations. Landing gear is used for parking, taxiing, takeoff, and landing. It may also be used to engage the surface of a water body.

To function safely, landing gear must be incredibly strong and robust. It must handle the massive stress of the aircraft's weight and the sudden touchdown shock during landing. To manage this impact, engineers use shock absorbers. Light planes often use solid shock absorbers. Larger aircraft use air and oil oleo struts to cushion the landing. The design of these components is crucial to the operational safety of the aircraft.

Most modern aircraft use retractable landing gear to improve performance. In early aircraft, the gear was usually fixed and remained protruding under the aircraft during flight. This created drag, which is air resistance that slows the vehicle down. Retractable gear folds into a compartment called a wheel well during flight. This maximizes aerodynamic streamlining, allowing for faster airspeeds and smoother flight control.

Most of this gear is hydraulically operated, meaning it uses liquid power. Some light aircraft use electrical or manual systems. If power fails in a light aircraft, an emergency extension system is always available. This might be a manual crank or a mechanical free-fall mechanism that uses gravity.

Engineers use several different wheel arrangements to balance stability and weight. A tricycle layout uses three sets of wheels, with one set in the nose and two main sets under the wings. This is the most common arrangement for modern aircraft. A "conventional" layout, or "taildragger," places two main wheels at the front and a smaller wheel or skid at the rear. This was common in the early propeller era to provide more propeller clearance. Some specialized planes use a bicycle layout, where the gear is located in tandem under the fuselage. The Lockheed U-2 and the Harrier jump jet are examples of this. Other configurations include the quadricycle layout, which uses four sets of wheels in a rectangular arrangement.

As aircraft have grown larger and heavier, landing gear designs have become much more complex. To avoid exceeding runway loading limits, engineers must spread the weight across many wheels. For example, the Zeppelin-Staaken R.VI used eighteen wheels to support its weight in 1916. The Boeing 747 uses four main landing gear posts and 16 wheels. The massive Antonov An-225 uses 28 main gear wheels.

Even the Airbus A380 uses a complex system with multiple bogies to support its size.

Landing gear is a significant part of an aircraft's economics and physics. It represents between 2.5% and 5% of the maximum takeoff weight (MTOW). It also accounts for 1.5% to 1.75% of the total aircraft cost. However, it is a very high-maintenance system. Landing gear accounts for 20% of the airframe's direct maintenance cost.

A single well-designed wheel can tolerate a ground speed of 300 km/h. These components are built to last, with a 20,000-hour time between overhauls and a 60,000-hour or 20-year lifetime.

Beyond standard runways, landing gear can be adapted for many different environments. Flying boats use a hull shape for buoyancy, while floatplanes use streamlined floats. Some aircraft are amphibious, meaning they have retractable wheels to operate on both land and water. Other experimental designs have explored using air cushions to move over obstacles or even tracked gear to reduce runway loading. These specialized systems allow aircraft to operate in places where traditional runways do not exist.