Oleo-Pneumatic Shock Struts and Their Functionality

Oleo-pneumatic shock struts, also referred to as oleo struts, are aircraft shock absorbers that assist in landings and ground maneuvers. As a type of oil/gas shock strut, such equipment is a crucial aspect of aircraft landing gear, ensuring that large forces are optimally relayed from the ground and into the airframe. As kinetic energy is transformed into heat by the strut, landing forces are absorbed and dissipated to dampen recoil and reduce bounce, relieving stress from the airframe and ensuring a smoother ride for passengers. In this blog, we will discuss the functionality of oleo struts, allowing you to better understand the role that they play in standard flight operations.

On an aircraft, there are many types of shock absorbers that may be present across the entire assembly. Oleo struts, in particular, are a fluid-spring shock absorber that is filled with hydraulic fluid and a gas such as air or nitrogen. As compared to such equipment, other various aircraft shock absorbers may be oil-filled liquid spring, air-filled pneumatic, or solid spring types. Solid-spring shock absorbers, in specific, are known for their low price point, high reliability, and low maintenance. Despite these advantages, they are fairly inefficient for intensive loads that are experienced in aircraft landing gear assemblies.

With their high efficiency for larger loads, oleo-pneumatic shock struts are the champion of modern aircraft. Alongside their efficiencies, they are also able to dissipate energy in such a way that it is stored and released at controlled rates during strut compression and expansion cycles. With this capability, oleo struts allow for a fairly constant impact force. Generally, this method of operation is comparable to buffers and equipment found in industrial, rail, and elevator assemblies.

In order to efficiently absorb and dissipate shock loads, oleo struts rely on gas and hydraulic fluids that are stored within a cylinder and piston. The lower piston is connected to the wheel mount axle, and it moves up and down within the upper cylinder which is connected to the aircraft landing gear. While the lower chamber contains hydraulic fluid, the upper cylinder is filled with gas. An orifice separates the two pieces, and hydraulic fluid is permitted to move between. To ensure that the piston and cylinder operate smoothly and without any leaks, bearings are implemented.

Upon landing on a runway or solid surface, the piston within the strut will be forced up into the cylinder, causing hydraulic fluid to move into the upper chamber. As it compresses the gas, forces are absorbed before the recoil causes the gas to expand and push fluids back. As fluids enter the piston again, the strut will extend, and heat will enter the airframe and atmosphere through convection and conduction. The orifice of the strut acts as a flow restrictor, determining the speed at which gas compression and expansion occurs.

Due to the immense forces that oleo struts undertake, it is important that they are regularly serviced to ensure airworthiness and operability. It is also crucial to confirm that there is always a correct fluid to gas ratio, those of which are determined by fluid levels and gas pressure. If you find yourself in need of various strut components for maintenance, seals, aircraft landing gear components, or other various aviation parts, look no further than Purchasing Efficiency.

Purchasing Efficiency provides oleo-pneumatic shock struts, aircraft bearings, aircraft fasteners parts, NSN parts, aviation parts, IT hardware parts, and more for various military and civilian applications. Take the time to explore our massive inventory of parts at your leisure, and you may request a quote on items for your comparisons at any time through the submission of an RFQ form as provided on our website. At Purchasing Efficiency, we are more than just a dependable distributor of parts, we are your strategic sourcing solution.