Sheet Metal 6.2: Aircraft Landing Gear Configurations SM6.2A

• Aircraft landing gear must be strong enough to withstand the forces of landing and ground operations when the aircraft is fully loaded.
• Landing gear is attached to primary structural members of the aircraft.
• A major design goal is to have the gear assembly be as light as possible, in addition to maintaining strength.
• Most landing gear have wheels to facilitate operation to and from hard surfaces, such as airport runways.

Landing Gear Configurations

• Numerous configurations of landing gear types can be found, including tricycle, taildragger, retractable, floats, monowheel with outriggers, and tandem with outriggers.
• There are two basic configurations of airplane landing gear: conventional gear (or tail wheel gear) and tricycle gear.

Conventional Gear

• Conventional gear aircraft have two main wheels positioned under most of the aircraft's weight, as well as a smaller wheel located at the aft end of the fuselage.
• Many aircraft designed for land use can be fitted with floats, either fixed or with retractable wheels, for amphibious use.
• Skis can also be fitted with wheels that retract to allow landing on solid ground or on snow and ice.

Tricycle Gear

• Tricycle gear is used in both light and heavy aircraft and is the most prevalent landing gear configuration in aviation.
• The main gear on a tricycle-type landing gear arrangement is attached to reinforced wing structure or fuselage structure.
• The number and location of wheels on the main gear vary, and many main gear have two or more wheels.

Fixed vs Retractable Gear

• Simple aircraft that fly at low speeds generally have fixed gear, meaning the gear is stationary and does not retract for flight.
• Retractable gear must be engineered to provide a strong attachment to the aircraft while still being able to move into a recess or well when stowed.
• A trunnion arrangement is typically used for retractable gear.

Trunnion

• The trunnion is a fixed structural extension of the upper strut cylinder with bearing surfaces that allow the entire gear assembly to move.
• It is attached to the aircraft structure in such a way that the gear can pivot from the vertical position required for landing and taxi to the stowed position used during flight.

Wheels and Brakes

• Wheels and tires are designed specifically for aviation use and have unique operating characteristics.
• Main wheel assemblies usually have a braking system.

Shock Absorption

• Most landing gear have a means of either absorbing shock or accepting shock and distributing it so that the structure is not damaged, crucial for handling the potentially high impact of landing.

Bungee Cords

• Bungee cords consist of a series of elastic cords wrapped between the airframe and the flexible gear system.
• They allow the gear to transfer impact load to the aircraft at a rate that does not damage the plane.

Other Shock Absorption Methods

• Rubber discs in compression with trailing link are used on the Mooney M20 series of aircraft.
• Some aircraft use a simple spring steel bar, which is mechanically simple, lightweight, and requires little to no maintenance.
• Other types include simple steel tubes and oleo strut landing gear.