dealing Aerospace O-ring materials must perform in extreme conditions and pass strict documentation requirements. They face jet fuel, hydraulic fluids, and temperatures from -65°F at altitude to the heat of an engine bay. Just as important, most applications call out a specific MIL-SPEC or AMS material. This article covers the compounds approved for aerospace hydraulic systems, jet fuel, low-temperature service, and a NASA-rated FFKM for hypergolic rocket propellants. For guidance beyond aerospace, visit our Complete Guide to Elastomer Seal Materials.
Aerospace O-Ring Materials
Aerospace seals must pass both physics and paperwork. They see -65°F at altitude, hot engine bays, and specialty fluids. Just as important, they must meet a named specification with traceable lot records. Marco’s Military and Aerospace Specification Reference Guide lists compounds approved to AMS, AS, MS, MIL, and NAS specs. Marco also stocks popular sizes from QPL manufacturers and offers MIL-P-4861 packaging on request.
Sealing Solutions That Meet MIL-SPEC Requirements for Aerospace Hydraulic Systems
Most military aircraft hydraulics run on petroleum-based fluids such as MIL-H-5606. For these systems, two NBR specifications dominate.
- AMS-P-83461 (Marco M1001): a QPL nitrile rated -65°F to 275°F. It offers better dynamic performance and
longer service life at 257°F than the older spec. It covers M83461/1 and M83461/2 sizes. - AMS-P-25732 (Marco M1000): the MS28775 spec, rated -65°F to 275°F. It remains a proven, recommended choice for military aircraft hydraulics, especially in low-temperature service.
When working with higher-temperature hydraulic and lube systems, FKM specifications apply. For example, Marco V1002 is a 75-durometer FKM made to AMS 7276 and MIL-R-83248C. In addition, V1004 and V1005 cover higher-temperature hydraulic service. For jet engine and APU applications, Markez® Z1217 FFKM meets AMS 7257.
Finally, pair high-pressure hydraulic O-rings with PTFE backup rings per MIL-R-879v1, such as MS28774 scarf-cut rings. See Marco’s backup rings for options.
Rubber Compounds Rated for Jet Fuel and Aviation Hydraulic Fluid
The right compound depends on the fluid. Jet fuel and petroleum hydraulic fluid favor one set of materials. By contrast, phosphate-ester fluids such as Skydrol® need a completely different polymer.
- Jet fuel, first choice: fluorosilicone (FVMQ) combines fuel resistance with excellent low-temperature flexibility. For example, F1001 is a 70-durometer blue fluorosilicone per AMS-R-25988, rated -100°F to 350°F. Marco also offers F1002, F1003, and F1004.
- Jet fuel, nitrile alternative: AMS 7270 nitrile (Marco M1007) is rated -40°F to 302°F for piston and jet engine fuels.
- Jet fuel and oils at high temperature: FKM to AMS 7276 or MIL-R-83248 adds heat and compression set resistance.
- Phosphate-ester hydraulic fluid (Skydrol): use EPDM (AMS 3248) or butyl (AMS 7263 or AMS 7277). Notably, NBR, FKM, and fluorosilicone are not compatible.
Best O-Ring and Seal Materials for Low-Temperature Aerospace Applications
Cold makes seals stiff, and stiff seals leak. Therefore, compare the TR-10 temperature, not just the catalog low limit.
For the coldest service, silicone leads. Extreme low-temperature grades such as AMS 3334 through AMS 3338 stay flexible well below -65°F. However, silicone has poor fuel resistance and wear. Where fuel is present, fluorosilicone is the better choice. For hot and cold fuel systems, low-temperature FKM grades help. For example, AMS-R-83485 covers FKM with improved low-temperature performance. Meanwhile, Marco’s ULT FKM (V1166) reaches -65°F with a TR-10 of -49°F.
Seals for Hypergolic Rocket Propellants
Space propulsion systems add another challenge: hypergolic propellants. For these systems, Freudenberg-NOK Sealing Technologies’ Simriz® 486 FFKM earned a NASA “A” compatibility rating in both MON-3 and MMH. It showed no deterioration of physical properties after 48 hours at 160°F (71°C). However, its low limit is +20°F (-7°C), so confirm that cold-soak conditions stay in range. Marco Sealing Solutions is an approved Freudenberg-NOK distributor, so you can buy Simriz® 486 online (a white, 75 Shore A FFKM compound from Freudenberg-NOK Sealing Technologies) or request a quote or engineering support directly from Marco.
Elastomer Materials by Industry and Application
Visit our Complete Guide to Elastomer Seal Materials to consult our quick reference tables for typical temperature ranges and elastomer seal materials by application. Read on to find application-specific recommendations for other industries.
- Elastomer Seal Materials for Medical Device & Pharmaceutical Processing
- Food and Beverage: O-Ring Materials Approved for Direct Food Contact
- Plasma-Resistant Seals and Elastomer Seal Materials for Semiconductor Fabs
- Elastomer Seal Materials for Oil & Gas: Subsea, Sour Gas, and Refinery Service
- Chemical-Resistant Seals for Aggressive Solvents in Chemical Processing
- Elastomer Seal Materials for Automotive & Industrial Equipment
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Engineered Sealing Solutions: Your Questions About Custom O-Rings, Compounds & Assemblies, Answered