ISO 8775:1988

Overview

ISO 8775:1988 - Aerospace: Gaseous oxygen replenishment connection for use in fluid systems (new type) - Dimensions (Inch series) - specifies the mechanical mating dimensions and required access clearance for an aircraft gaseous oxygen replenishment coupling. Published as the first edition in 1988, the standard replaces ISO 1022 for new designs and defines the physical interface (inch series) to ensure interchangeability and safe installation of oxygen replenishment connections.

Key topics and technical requirements

• Mating dimensions: The geometry of the coupling mating end is defined by the figures and tabulated dimensions (figure 1, table 1). Surface profile, run-out tolerances and roughness requirements are specified for the mating surfaces.
• Thread options: The connecting thread shall be one of two types:
  • 3/8-24 UNF-3A, per the general requirements and dimensions of ISO 725 (inch screw threads), or
  • 0.375-24 UNJF-3A, in accordance with ISO 3161 (UNJ threads for aerospace).
• Run-out and surface texture: Run-out tolerances are referenced to ISO 1101 (geometrical tolerancing). Surface finish requirements (Ra) reference ISO 1302.
• Access clearance: Minimum clearance dimensions around the coupling (for tools, connection/disconnection and operational access) are defined in figure 2 and table 3. These clearances ensure practical accessibility for replenishment operations.
• Figures and tables: The standard relies on precise drawings and numeric tables to eliminate ambiguity in production and inspection.

Applications and who uses it

ISO 8775:1988 is used by:

• Aerospace design engineers specifying oxygen replenishment interfaces on aircraft and spacecraft
• Component and coupling manufacturers producing compatible gaseous oxygen connectors
• Maintenance and overhaul organizations performing oxygen system replenishment, inspection and replacement
• Certification bodies and procurement teams requiring standardized mechanical interfaces for safety and interoperability
• System integrators and avionics/oxygen-system equipment suppliers ensuring compatibility across platforms

Practical applications include design and manufacturing of oxygen replenishment panels, service ports, refueling adapters and maintenance tool clearances where adherence to defined thread forms, mating geometries and surface requirements is critical.

Related standards

• ISO 725 - Inch screw threads - Basic dimensions
• ISO 3161 - UNJ threads for aerospace (inch series)
• ISO 1101 - Geometrical tolerancing (run-out, form and position)
• ISO 1302 - Indicating surface texture on technical drawings
• Replaces: ISO 1022 (for new designs)

Keywords: ISO 8775:1988, gaseous oxygen replenishment connection, aerospace coupling dimensions, inch series, 3/8-24 UNF-3A, UNJF, access clearance, mating dimensions, ISO 725, ISO 3161.