Aircraft Landing Gear Fluid: Aero 40 BMS 3-32 Type II Overview
Aircraft landing gear takes a serious beating. From a relatively light T-6 Texan II, T-1 Jayhawk, or even a UC-35 Citation, to much heavier airframes, especially those that land in places other than hard surfaces (C-17, C-130, UH-60, CH-47), the landing gear takes an absolute beating.
These systems rely on a relatively simple mixture of fluid and gas to absorb the extreme shock caused by ceasing to fly. Greenwood Aerospace has you covered for all your hydraulic fluid needs for military, federal, or approved state missions.
What Aero 40 Is And Why It Matters For Landing Gear
Aero 40 is a high-performance, mineral-based hydraulic fluid formulated for aircraft landing gear shock struts and other demanding hydraulic systems. It belongs to a class of petroleum-based fluids, often characterized by its distinctive red color, and is known for its stable performance across a wide range of operating temperatures and pressures.
The primary function of a shock strut in landing gear is to convert the kinetic energy of a hard landing into heat through damping. Aero 40 acts as an incompressible medium forced through small orifices, creating hydraulic resistance that controls how quickly the shock strut compresses and extends. This controlled damping is essential for absorbing massive shock loads, especially on airframes operating off hard runways, such as the C-17, C-130, UH-60, and CH-47.
Common aircraft applications for fluids like Aero 40 include the landing gear of various military and commercial aircraft, from lighter airframes like the T-6 Texan II and T-1A Jayhawk to heavier transport aircraft.
BMS 3-32 Type II Certification And MIL PRF Context
BMS 3-32 Type II is a tough spec used in the aerospace industry to qualify mineral hydraulic fluids. The “Type II” designation means higher performance within the BMS 3-32 family, with better thermal stability, oxidation resistance, and fluid compatibility. Meeting BMS 3-32 Type II means the fluid can withstand the extreme conditions of high-cycle, high-stress components like landing gear shock struts without degrading.
The MIL-PRF (Military Performance Specification) context matters because MIL-PRF specs set baseline quality and performance standards for fluids used in military and, by extension, many commercial aircraft. MIL-PRF specs, such as the MIL-PRF-5606 series, specify the performance and testing requirements for hydraulic fluids. The BMS 3-32 Type II spec references and supersedes certain MIL-PRF requirements; it’s a specific, demanding qualification. Typical test specs referenced by BMS 3-32 include corrosion protection, shear stability, foam resistance, and low-temperature fluidity to ensure performance and material compatibility in all operational environments.
Mineral Hydraulic Fluid Versus Other Hydraulic Fluids
Mineral hydraulic fluids like Aero 40 are made from highly refined petroleum base stocks with various chemical additives. These additives typically include rust and oxidation inhibitors, anti-wear agents, and pour point depressants to ensure performance. The mineral base stock provides lubrication and cost-effectiveness.
Phosphate ester fluids are synthetic fluids known for their fire resistance. They are non-flammable and the standard choice for systems operating near high-heat sources, such as turbine engines or utility systems in commercial airliners. However, phosphate ester fluids are chemically aggressive and require special seals and materials, whereas mineral fluids are compatible with a wider range of conventional elastomers.
One big plus of high-quality mineral fluids like Aero 40 is their low-temperature performance. All hydraulic fluids have viscosity challenges in the cold, but specialized mineral fluids are formulated to remain fluid and function at very low ambient temperatures, which is critical for cold-weather operations. Regarding viscosity behavior, mineral fluids are engineered to have a high viscosity index (VI), meaning their viscosity changes less over a wide temperature range, resulting in consistent damping and system responsiveness from cold start to high-speed operation.
Performance Specifications For Landing Gear Shock Struts
Maintenance And Contamination Control For Shock Struts
The OEM determines this maintenance process and lays it out in technical data. Shock struts are usually drained and serviced during phase inspection for military aircraft, though they can also be done for mechanical defects or on more frequent cycles, depending on the airframe, landing cycles, and myriad other factors.
Work with your maintenance production team to determine the frequency for the airframe(s) in question to gauge your procurement needs.
Procurement, Part Numbers, And Supply Chain Guidance
Greenwood Aerospace is your trusted source for AeroShell 40 and other landing gear fluid brands. We provide them via GSA Advantage, so your organization can quickly and easily source these products for your team.
If your team is approved (or obligated) to use GSA Advantage, review our listings below and fully stock your landing gear fluid.
ITAR-registered and AS9120B-certified, Greenwood Aerospace supports defense contractors with compliant export solutions for military programs.
GSA Contract Number: 47QSMS25D00B8
UEI: KVSUYYSJS174 · DUNS: 604006874 · Cage Code: 2Y735
ITAR DDTC Export Compliant · NAICS: 488190, 336413, 332722, 336411, 481212, 532411
Availability, expedited shipping, or large orders? Email us at gsasales@greenwood.aero or call us at 580-865-6000 | 833-GSA-EBUY
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