Overview
ISO 9475:1994 specifies standardized test methods for valve cores and caps used on aircraft inner-tube and tubeless tyres, and defines minimum airtightness requirements. The standard establishes a common test procedure so products from different manufacturers can be evaluated and compared on the same basis. It covers test setups, performance criteria and environmental conditioning relevant to aviation tyre valves.
Key topics and technical requirements
- Scope: Test methods for valve cores and taps (caps) for aircraft tyres, with or without inner tubes; minimum airtightness standard.
- Airtightness limit: Valve cores are rejected if leakage exceeds 0.2 cm3/min under specified test conditions.
- Core tests (performed generally on six cores in a manifold):
- Tightening torque test - torque ranges specified: elastomeric seat cores 0.17–0.34 N·m; metal-stop or metal-seat cores 0.34–0.54 N·m.
- Washout test - simulates rapid deflation at high pressure (manifold at 3 800 kPa; 10 cycles).
- Blowout test - simulates rapid inflation/pressure changes (10 cycles).
- Pressurized pulse test - multi-pressure cycling including low/normal/high sequences (e.g., 200 kPa up to 3 800 kPa).
- Environmental tests - low temperature (hold at -54 °C), constant high temperature (hold at +93 °C) and peak temperature cycles (short exposure to +120 °C), with airtightness checks at defined pressures.
- Tap (cap) tests:
- Determination of gasket mechanical properties (tensile strength, elongation, hardness, compression set) referencing ISO material tests.
- Temperature resistance and ageing (service range -54 °C to +93 °C; oven ageing at +93 °C).
- Screwing/unscrewing cycles; cap tightening torque indicated between 0.56 N·m and 0.79 N·m.
- General test conditions: ambient or specified temperatures, manifold configurations, and repeatable cycle counts to ensure comparability.
Applications and who uses it
- Aircraft tyre and valve manufacturers - design validation and production quality control.
- Component suppliers and OEMs - acceptance testing and supplier qualification.
- Maintenance, repair and overhaul (MRO) organizations - verifying component performance before installation.
- Regulatory authorities and certification bodies - harmonized test evidence for airworthiness and procurement specifications.
- Test laboratories - implementing repeatable methods for comparative evaluation and failure analysis.
Related standards
- ISO 37 (tensile properties of rubber)
- ISO 48 (rubber hardness)
- ISO 815 (compression set)
- ISO 868 (plastics/ebonite indentation hardness)
Keywords: ISO 9475:1994, aircraft tyre valve cores, tubeless tyre valve, valve caps test methods, airtightness standard, washout test, pressurized pulse, leak rate.