Overview
ISO 485:1973 - Aircraft water‑methanol pressure connections specifies the mechanical interface dimensions and clearances for two standardized bore sizes used in aircraft water‑methanol pressure systems: 19 mm (3/4 in) and 38 mm (1 1/2 in). The standard defines connector geometry, space envelopes (clearance zones), and dimensional tolerances to ensure interchangeability between aircraft-mounted mating units and hose‑unit couplings.
Key topics and technical requirements
- Bore sizes and flow rates
- 19 mm (3/4 in) connectors: rated for flows up to 114 L/min (25 gal UK/min).
- 38 mm (1 1/2 in) connectors: rated for flows up to 546 L/min (120 gal UK/min).
- Dimensions and drawings
- Detailed connector and envelope geometry shown in Figures 1–4; accompanying tables list all nominal dimensions and limits.
- Space envelopes (minimum clearance outlines) for hose units are specified for each size.
- Tolerances
- General dimensional tolerance: ±0.1 mm (±0.005 in).
- Angular tolerance: ±0°15′.
- Valve and locking features
- Locking flange reference plane, selective pin/slot arrangement and valve face location are defined.
- Spring‑loading requirements: for the 19 mm connector the valve loading must meet specified limits (shut position 15.5–22.3 N, and a maximum at specified travel of 44.5 N); for the 38 mm connector the loading at 23.93 mm travel must not exceed 98 N, with shut‑position loading 40–49 N.
- Erratum
- An erratum published in 1980 adds a limit r5 max = 0.38 mm (0.015 in) for a valve‑seat detail.
Applications
- Ensures mechanical compatibility and safe operation of aircraft water‑methanol pressure systems where standardized hose units mate with aircraft‑mounted couplings.
- Used during design, manufacture and inspection of:
- Hose assemblies and couplings for water‑methanol delivery
- Aircraft mating units and bulkhead fittings
- Maintenance, repair and overhaul (MRO) procedures that require replacement or inspection of connectors
- Helps procurement and certification by providing deterministic dimensional and performance criteria for connector interchangeability.
Who uses this standard
- Aircraft systems and airframe designers
- Hose and coupling manufacturers
- Maintenance engineers and MRO organizations
- Certification authorities and procurement teams responsible for spare parts compatibility
Related information
- ISO 485:1973 was prepared by ISO/TC 20 (Aircraft and space vehicles) and replaces the earlier recommendation R 485‑1966. For broader compatibility and regulatory context, consult other ISO and aviation industry standards on aircraft fluid connectors and fittings published by ISO/TC 20.
