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The Function of Aircraft Landing Gear

The landing gear of an aircraft is an often overlooked, but major, component of the vehicle that allows it to take off and land safely. In addition, landing gear support for taxiing or parking makes this assembly very important in an airplane's standard operations. Landing gear often comes in various types and different assemblies may be used in various aircraft depending on requirements, but all serve one function: helping planes take off and touch down on runways safely after a flight. Landing gear can generally be divided into two groups based on retraction capabilities, those of which are fixed type landing gear and retractable type landing gear. Today, mostly all modern commercial aircraft use wheel-type retractable landing gear. This blog will shed light on the importance of landing gear and how it functions.

The weight of a plane's landing gear can be up to 5% or more of the total aircraft take-off weight. Even though landing gear is a crucial component, it is dead weight when airborne. This makes it an unnecessary drag on flights if the assembly hangs out in the air underneath the aircraft. Thus, using retractable landing gear and stowing it inside an aircraft reduces air drag and allows for increased climb performance and higher cruise airspeeds. The different types of landing gear that an aircraft may take advantage of include wheels, skids, and skis for snowy conditions and floats to provide water support when landing on lakes and rivers. Helicopters, balloon gondolas, and tail dragger aircraft use skid-type landing gear for landing. These come in several shapes with various sizes depending upon their purpose.

Retractable landing gear systems are an excellent way to provide your plane with the most modern and efficient means of stowing during flight. The system can be operated hydraulically, electrically, or with both systems combined into one unit. The cockpit flightdeck is provided with warning indicators to inform the position of the landing gear to the pilot if the gears are up and locked, down and locked, or in an intermediate position. With an electrical landing gear system, the up and down motion of the gear is controlled by an electrically-driven motor through an electrically-driven jack for raising and lowering the assembly. The motor starts operating when the pilot moves the switch to the up position in the flight deck. A force is transmitted through the shaft, gears, adapters, an actuator screw, and a torque tube to the drag strut linkages for retracting and locking the gear. When the pilot moves the switch to the down position, the motor moves the gear down in the reverse direction. Once activated, the motor will continue operating until an up or down limit switch on its gearbox gets tripped--which means pilots need to be very careful while working with landing gear.

With a hydraulic landing gear retraction system, pressurized fluids are used to actuate linkages and raise or lower the aircraft's landing gear assembly. When the pilot moves the switch up, it triggers the hydraulic system, and hydraulic fluid is driven up the line through sequenced valves to the gear actuating cylinder for the retraction process. Similarly, when the switch is moved to the down position, the process repeats for the landing gear extension process. The hydraulic pump that pressurizes the fluid in a hydraulic system can be engine-driven or electrical. If an electric pump is used, it is called an electrohydraulic system. Hydraulic landing gear assemblies also incorporate a hydraulic reservoir containing excess fluid and provide accurate readings for monitoring purposes.

The hydraulic pump has a safety feature that prevents it from overpressuring. When the pressure reaches excessive levels, relief valves open and route excess fluid back into the reservoir, and there is another relief valve to prevent excessive pressure caused by thermal expansion. Hydraulic pressure is also controlled using limit switches. The system has two limit switches, one for extension and another for retraction, which de-energize the hydraulic pump after its landing gear cycle.

The landing gear is the principal support system for an airplane during landing. It absorbs impact energy to reduce loads transmitted onto the airframe and helps maintain the plane's integrity when touching down on the runway with high precision. The main components of landing gear in a modern commercial aircraft include a shock absorber, axle, torque links, side braces, retraction actuators, wheels, tires, a brake system, anti-skid systems, and steering systems. In addition, the pilot is provided with an emergency gear extension system in case of issues. If the landing gear is somehow not extending even after moving the switch, the emergency extension system lowers the landing gear. The emergency release handle in the flight deck of some airplanes is connected through mechanical linkages to gear-up locks. When activated, it releases these safety mechanisms and allows the landing gear assembly to free fall or extend under its own weight.

The importance of landing gear cannot be overstated since it is the main support system of your aircraft that permits landing, taking off, and other ground-operations. ASAP Global Supplies takes pride in providing high-quality, authentic products from trusted aircraft parts manufacturers. If you are looking for a reliable and trusted aviation parts supplier, get in touch with a team member or visit our website to check our inventory. Feel free to call at your convenience, as our dedicated account managers are available 24/7x365 to resolve your queries.


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March 3, 2022
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