What goes up must inevitably come back down. An aircraft’s landing gear ensures that the “coming back down” part ends safely and allows the aircraft to maneuver safely on the ground. Landing gear on aircraft comes in several different types and configurations, which this blog will explore.
What are the types of landing gear?
The first type of widely used landing gear is tailwheel-type landing gear, also called conventional gear because so many early aircraft used it. Tailwheel fitting actuator landing gear places the center of gravity behind the main wheels, causing the tail to require support from a third wheel assembly. A few early aircraft designs used a skid rather than a wheel, but improvements to landing runways and wheel durability negated the need for them. A tailwheel configuration causes the aircraft’s nose to angle upwards when on the ground, which elevates the engine and allows a larger propeller to be installed, which compensates for older, unpowered engines. This greater clearance also allows the aircraft to operate in and out of unpaved runways, and in the wilderness for bush flying. For these reasons, and for the fact that a light tail assembly saves weight, tailwheel aircraft are still made to this day.
However, tricycle-type landing gear is the most frequently used type in modern aircraft. In a tricycle aircraft, the center of gravity is in front of the main gear, requiring a wheel in the nose to support the aircraft’s weight and balance it on the ground. Tricycle landing gear have several advantages: they allow for more forceful application of the brakes without nosing over when braking, they provide better visibility from the cockpit during landing and ground maneuvering, and they prevent ground-looping on the aircraft since forces affecting the aircraft’s center of gravity push it forward rather than causing it to loop. Most aircraft have steerable nose gear, either attached via mechanical linkage to the rudder panels, or by hydraulic power linked to an independent tiller in the cockpit.
How does aircraft landing gear work?
Main landing gear are attached to a reinforced wing or fuselage structure and will often have two or more wheels to spread the aircraft’s propellers weight over a larger area and provide a safety margin should one tire fail. When more than two wheels are attached to a landing gear strut, it is called a bogie. The number of wheels on a bogie is a function of the gross weight of the aircraft, and the surface type the aircraft is intended to land on. The Boeing 777, for instance, uses a triple bogie main gear featuring six wheels.
Alternative landing gear types do exist. Tandem landing gear sets, featuring a main and tail gear aligned on the longitudinal axis of the aircraft, are used by sailplanes, several military bombers like the B-47 and B-52, and the VTOL Harrier jet. Helicopters use landing skids, and seaplanes will mount floats rather than wheels to be able to take off and land on water.