What Goes Up, Must Come Down
The landing gear of an aircraft supports the entire weight of a vehicle during landing and ground operations. The components are primarily attached to the actual structure of the aircraft and has different applications for each part. Wheels are most commonly associated with aircraft landing gear but, there are many other facets involved. Modern landing gear technology wouldn’t be possible if shock absorbing equipment didn’t exist, making shock absorption a crucial aspect of both landing and takeoff.
A shock absorber is a hydraulic device that is designed to absorb and dissipate shock impulses. It converts the kinetic energy of the shock into another form of energy, typically heat, which is then dispelled. Hydraulic shock absorbers are used in conjunction with springs and cushions. One thing to consider when choosing a shock strut or absorber is where that energy will go. In many shock absorbers, the energy it absorbs is converted to heat inside the viscous fluid. In hydraulic cylinders, the hydraulic fluid is heated while hot air is exhausted to the atmosphere.
Shock struts are self-contained hydraulic units that support an aircraft while it is on the ground; they also protect the structure of the plane during landing. Shock absorption occurs when the force of an impact landing is converted into heat energy that makes its way towards the strut landing gear.
An oleo strut is a type of absorber that is equipped on most commercial aircraft. A steel coil spring stores the impact energy then releases it into the oleo strut, where it is absorbed. The design of the spring allows it to cushion the impact of landing and decompress the vertical oscillations that are produced, allowing for a smooth landing. As the strut is compressed, the spring rate has a dramatic increase, while the hydraulic oil of the oleo strut reduces the rebound motion.
Nose gear shock struts are attached to the wheel in the very front portion of the landing gear, directly under the cockpit of the plane. It is composed of a locating cam assembly which enables it to keep the gear that it is attached to aligned. The cam assembly maintains a forward position when the shock strut is fully extended and allows the nose of the wheel to fit snug in the wheel well when it is retracted.
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