Aerospace Rubber Components
Aerospace rubber seals, gaskets, and molded components are among the most specification-controlled rubber parts in any industry. Every compound choice is governed by an AMS specification that defines not just material properties but test protocols, traceability requirements, and acceptable cure systems. A seal that performs flawlessly in a ground vehicle hydraulic system may be unsuitable for the same function in an aircraft because of outgassing behavior, low-temperature stiffness, or the absence of the specific AMS qualification documentation that the airframe OEM requires before installation.
Wayne Rubber manufactures custom rubber seals, gaskets, o-rings, vibration isolators, and molded components for commercial and military aerospace programs from Wixom, Michigan. AMS-specification compounds in FKM, FVMQ, silicone, EPDM, and nitrile, with Certificate of Conformance and material traceability documentation. Wayne Rubber supports both OEM production programs and MRO replacement parts.
The AMS Specification System for Aerospace Elastomers
Aerospace elastomers are qualified to SAE Aerospace Material Specifications (AMS), which define compound requirements more precisely than MIL specifications for most aircraft program applications. An AMS number on an engineering drawing means the compound must be produced from an AMS-qualified formulation, tested to the specification’s physical property requirements, and documented with a Certificate of Conformance citing the specific AMS number. Using a non-AMS compound in an AMS-cited location (even if the physical properties are equivalent) is a nonconformance under AS9100.
The primary AMS specification for FKM (fluoroelastomer) o-rings and seals in aircraft hydraulic systems using MIL-PRF-83282 and MIL-PRF-87257 synthetic hydraulic fluids. Defines physical properties, fluid immersion requirements, and compression set limits for FKM compounds in aircraft hydraulic applications. Complementary to MIL-DTL-5512 Class 1 hydraulic packing. Used throughout commercial and military fixed-wing and rotary-wing hydraulic systems. FKM per AMS 7257 replaces older NBR-based compounds in aircraft hydraulic systems where synthetic fluid compatibility is required at temperatures above NBR’s service limit.
FKM compound specification for aircraft engine and engine accessory sealing applications at sustained high temperatures. Defines property requirements for FKM o-rings and seals exposed to engine oils (MIL-PRF-7808, MIL-PRF-23699) and lubricants at temperatures that exceed AMS 7257 ratings. Used for engine oil system seals, gearbox seals, and engine-mounted accessory drive seals on turbofan and turboprop aircraft engines. The high-temperature FKM complement to AMS 7257 for engine applications rather than airframe hydraulic system applications.
Three related AMS specifications covering fluorosilicone (FVMQ) o-ring compounds for aircraft fuel system sealing. AMS 3325 covers 60-durometer FVMQ for general fuel system applications; AMS 3326 covers 70-durometer; AMS 3327 covers 80-durometer. All three are qualified for aviation fuel grades including Jet A, JP-4, JP-5, and JP-8 across the full operating temperature range from -65°F arctic cold-soak through sustained operating temperatures. These are the controlling AMS specifications for aircraft fuel system o-rings that must simultaneously resist aviation fuel and provide flexibility at extreme low temperatures, the defining capability that distinguishes FVMQ from FKM in fuel system applications.
Silicone rubber compound specification for general aircraft sealing applications including airframe door and window seals, access panel seals, and environmental sealing throughout the aircraft structure. Defines property requirements by compound class and durometer. Used where the wide temperature range of silicone is required without the fuel resistance requirement that would demand FVMQ. Airframe seals, window seals, cabin environmental seals, and avionics compartment gaskets are the primary applications. Related to A-A-59588 (the CID version) but specifically an AMS designation for aerospace drawing citations requiring AMS-level qualification.
Nitrile rubber (NBR) compound specification for aircraft hydraulic systems using petroleum-base hydraulic fluid (MIL-PRF-5606). Defines physical property requirements and fluid immersion limits for NBR o-rings in aircraft hydraulic applications. Increasingly being superseded by AMS 7257 (FKM) as aircraft hydraulic systems transition from petroleum to synthetic fluid, but remains the controlling specification for legacy aircraft and for MRO replacement parts on platforms still using MIL-PRF-5606. Important for MRO operations supporting aging aircraft where the original design specification cited AMS 3304 and only AMS 3304-qualified compound is acceptable.
AMS 7259 and NAS 1613 specify dimensional requirements and tolerances for aerospace o-rings independently of compound. A drawing may cite both an AMS compound specification (AMS 7257, AMS 3325, etc.) and a dimensional standard (AS568 or NAS 1613) on the same part. NAS 1613 o-rings have tighter dimensional tolerances than standard AS568 commercial o-rings and are required for many aircraft hydraulic and fuel system fittings where the o-ring must seat consistently in close-tolerance grooves. The combination of AMS compound qualification and NAS 1613 dimensional compliance defines the full specification for an aerospace o-ring that is not just a standard AS568 part in an AMS material.
Aerospace Rubber Applications by Aircraft System
Every zone of a modern aircraft creates a distinct sealing environment with different temperature extremes, fluid exposures, and regulatory requirements. The compound that is correct for the fuel system is wrong for the pressurized cabin; the compound correct for the engine hot section is wrong for the fuel system at cold-soak. An aircraft-system-by-system compound map is the most useful framework for aerospace rubber specification.
- Engine oil system seals: FKM per AMS 7276 for engine oil (MIL-PRF-7808 or MIL-PRF-23699) at sustained high temperatures; compression set and thermal stability over 10,000-hour engine intervals are the critical performance metrics
- Turbine engine fuel system seals: FVMQ per AMS 3325/3326 for fuel-wetted seals in the engine fuel system near heat sources; combined Jet A resistance and 400°F capability with low-temperature cold-soak flexibility
- Engine mount isolators: silicone per A-A-59588 Class 3A for engine attachment lug isolators and exhaust hanger mounts; wide temperature range and tear resistance under sustained vibration loading
- Engine accessory gearbox seals: FKM per AMS 7276 for accessory gearbox and IDG (integrated drive generator) oil seals at elevated temperatures near the engine core
- Thrust reverser seals: high-temperature silicone or FKM gaskets for thrust reverser actuation system and duct sealing; must survive both hot exhaust gas exposure during reverser operation and cold-soak between flights
- Nacelle and cowl seals: silicone per AMS 3337 for nacelle access panel seals and cowl door weatherstripping; UV, ozone, and wide temperature range required for exterior nacelle locations
- Wing tank access panel gaskets: FVMQ per AMS 3325 for fuel tank access door seals in wing integral fuel tanks; continuous fuel immersion in Jet A or JP-8, plus cold-soak to -65°F at altitude
- Fuel cell bladder fittings: FVMQ o-rings for collapsible fuel cell fitting connections in military aircraft with self-sealing fuel tanks; fuel resistance combined with ballistic damage flexibility requirements
- Fuel transfer and boost pump seals: FVMQ per AMS 3325/3326 for pump shaft seals and fuel system valve seals; continuous fuel contact at operating pressure and temperature range
- Fuel quantity sensor seals: FVMQ for capacitance-type fuel quantity measurement sensor probe seals in wing tanks; low-extractable requirement to prevent sensor contamination
- Fuel filler and vent seals: FVMQ for pressure refuel/defuel adapter seals and fuel vent system seals; fuel resistance combined with outdoor UV and temperature cycling
- Aerial refueling system seals: FVMQ per AMS 3325/3327 for receptacle and probe seal applications; must maintain sealing integrity under refueling pressure surges and cold-altitude conditions
- Flight control actuator seals: FKM per AMS 7257 for flight control surface actuator rod and piston seals; synthetic hydraulic fluid (MIL-PRF-83282) compatibility with wide temperature range and low compression set required for reliable control surface movement
- Landing gear actuator seals: FKM per AMS 7257 for main and nose gear actuator sealing; shock loading during gear extension and retraction combined with sustained parking-brake hydraulic pressure
- Hydraulic reservoir and accumulator seals: FKM for main hydraulic system reservoir seals and accumulator bladders; synthetic fluid compatibility with minimal permeation through the seal body
- Brake system seals: FKM for aircraft brake actuator and metering valve seals; high-temperature brake fluid exposure during heavy braking combined with static sealing during parked aircraft
- Nose wheel steering seals: FKM for nose gear steering actuator seals; combined hydraulic fluid and ground contamination (de-icing fluid, anti-icing compounds) exposure during ground operations
- Power transfer unit seals: FKM for cross-system hydraulic power transfer unit sealing; must accommodate both engine-driven hydraulic pressure and ram air turbine-driven emergency pressure
- Pressurized cabin door seals: silicone sponge per AMS 3337 for passenger cabin door and emergency exit inflatable seal systems; must maintain cabin pressure differential from sea level to cruise altitude across tens of thousands of pressurization cycles
- Window and windshield seals: silicone for cockpit windshield and cabin window sealing; UV stability, ozone resistance, and wide temperature range from ground temperature extremes to -65°F cruise altitude
- Avionics bay gaskets and seals: low-outgassing silicone for avionics equipment bay enclosures where outgassing from the seal could deposit on sensitive electronic components or contaminate optical sensors; platinum-cured silicone preferred for minimum extractables in enclosed avionics spaces
- Antenna base seals: silicone for flush-mounted antenna base sealing on fuselage skin; must survive pressurization cycling, UV, and aerodynamic loading without lifting or cracking
- APU (auxiliary power unit) seals: FKM or high-temperature silicone for APU fuel, oil, and exhaust system sealing; APU operates in the tail cone at ground temperatures from arctic to desert environments
- Environmental control system seals: EPDM or silicone for bleed air duct connections and pack bay environmental control system sealing; hot bleed air at moderate pressure combined with wide ambient temperature range
Outgassing: The Specification Requirement Most Non-Aerospace Suppliers Miss
Outgassing is the release of volatile compounds from a cured rubber part into the surrounding environment. In most industrial applications, outgassing from rubber components is negligible and irrelevant. In enclosed aerospace environments (avionics bays, sealed instrument enclosures, optical sensor housings, and spacecraft), outgassing from elastomeric seals is a critical qualification parameter that can contaminate electronics, deposit films on optical surfaces, and cause electronic component failures over long service intervals.
NASA specification ASTM E595 and the European equivalent ESA-developed test protocol measure two parameters: Total Mass Loss (TML), which is the percentage of mass lost from a specimen after 24 hours at 125°C in vacuum; and Collected Volatile Condensable Material (CVCM), which measures the mass of material that condenses on a cooled collector plate. For space and critical avionics applications, the standard acceptance criteria are TML below 1.0% and CVCM below 0.1%.
Peroxide-cured silicone compounds have measurably higher outgassing than platinum addition-cured silicone. The peroxide decomposition byproducts (primarily methyl acetate and dimethyl siloxane oligomers) remain in the cured compound as volatile extractables that outgas slowly over time at elevated temperatures. Post-curing at 200°C drives out the majority of these volatiles, but residual levels in inadequately post-cured compounds can fail ASTM E595 acceptance criteria.
Platinum-cured silicone (LSR or platinum-cured HCR) produces no byproduct molecules and has dramatically lower outgassing than peroxide-cured compounds with equivalent post-cure. For any aerospace application involving enclosed electronics, optical sensors, or satellite components, platinum-cured silicone should be specified with ASTM E595 test data on the compound provided as part of the material certification package. Wayne Rubber can source platinum-cured silicone compounds with ASTM E595 outgassing data and provide this documentation with qualified shipments.
Aerospace Compound Selection by Aircraft System
| Compound | AMS Specification | Primary Aerospace Applications | Key Performance Requirement |
|---|---|---|---|
| FKM | AMS 7257 (hydraulic), AMS 7276 (engine/high-temp) | Aircraft hydraulic actuator seals (synthetic fluid), flight control actuator seals, landing gear seals, engine oil system seals, brake system seals | Synthetic hydraulic fluid compatibility (MIL-PRF-83282/87257); engine oil compatibility at high temperatures; low compression set over 10,000+ hour service intervals; low gas permeability for pressurized system containment |
| FVMQ | AMS 3325 (60A), AMS 3326 (70A), AMS 3327 (80A) | Wing tank fuel system seals, fuel transfer pump seals, aerial refueling system seals, fuel cell fittings, engine fuel system seals near heat sources | Aviation fuel resistance (Jet A, JP-4/5/8) combined with -65°F cold-soak flexibility; the only AMS-qualified compound satisfying both fuel resistance and arctic low-temperature requirements simultaneously |
| Silicone (VMQ) | AMS 3337, A-A-59588 (Classes 1A through 3B) | Pressurized cabin door seals, cockpit window seals, avionics bay gaskets (low-outgassing platinum cure), antenna base seals, engine mount isolators, nacelle access panel weatherstripping | Wide temperature range (-65°F to +450°F); low outgassing for avionics and optical applications (platinum cure + ASTM E595 data); UV and ozone stability for exterior airframe sealing; tear resistance for dynamic door seal cycles (Class 3A/3B) |
| NBR | AMS 3304 | Legacy aircraft hydraulic seals using MIL-PRF-5606 petroleum hydraulic fluid; MRO replacement parts on older aircraft where AMS 3304 was the original specification; not specified for new production aircraft with synthetic hydraulic fluid | MIL-PRF-5606 petroleum hydraulic fluid compatibility; MRO applications require compound qualification specifically to AMS 3304, not simply a general-purpose nitrile compound that may not be AMS-qualified |
| EPDM | Various AMS grades by application | Environmental control system duct seals, bleed air system seals, APU compartment environmental sealing, heated air distribution system connections | Resistance to high-temperature bleed air (up to 400°F in bleed air ducts near engine stations); ozone and UV resistance for external duct connections; steam and hot air resistance without oil or fuel contact |
| FFKM | USP Class VI; customer-specific qualification | Ultra-high-temperature engine accessory seals above FKM’s 400°F limit; analytical instrument seals in aircraft health monitoring systems; satellite and spacecraft propulsion system seals requiring near-universal chemical resistance | Service temperatures above 400°F continuous; chemical resistance to the full range of aerospace fluids and cleaning agents simultaneously; ultra-low outgassing for satellite optical and sensor systems |
Aerospace Documentation Capabilities
What Wayne Rubber Provides for Aerospace Programs
Certificate of Conformance (CoC) with AMS Citation: Every aerospace shipment includes a CoC citing the applicable AMS specification number, compound lot number, cure date, and shelf life expiration. The CoC is signed by an authorized representative and is formatted to support AS9100 receiving inspection documentation requirements.
Material Traceability: Full batch-level traceability from compound supplier through production. Required for all AS9100-controlled programs and essential for airworthiness documentation on FAA/EASA-regulated parts. Wayne Rubber maintains compound certificates of conformance from qualified elastomer suppliers.
First Article Inspection (FAI) per AS9102: Dimensional and physical property verification of first articles from new tooling or programs, documented to AS9102 format. Required for most OEM production program entry and for return-to-production programs after extended inactivity.
Shelf Life Management: Aerospace elastomers have regulatory shelf life limits (typically 15 years for silicone, 5 years for NBR and neoprene, 10 years for FKM). Wayne Rubber provides cure date on all CoC documentation, supporting shelf life tracking for MRO receiving inspection. Parts approaching shelf life expiration can be identified from CoC records before installation.
Outgassing Data (ASTM E595): For avionics, optical, and spacecraft applications requiring outgassing qualification, Wayne Rubber can source compounds with existing ASTM E595 test data and provide this documentation alongside the CoC. New compound outgassing testing can be arranged through qualified test laboratories for program-specific qualification.
Aerospace Rubber Products from Wayne Rubber
Aerospace Elastomers at Wayne Rubber
Request Aerospace Rubber Components from Wayne Rubber
Provide the applicable AMS specification, aircraft system location, fluid environment, operating temperature range, dimensional drawing, and documentation requirements (CoC, FAI, outgassing data). Wayne Rubber will confirm the qualified compound and provide a full aerospace documentation package.