ISO 8668-5:1992

Overview - ISO 8668-5:1992 (Aircraft terminal junction systems, Type 3)

ISO 8668-5:1992 defines the detail specification for Type 3 Terminal Junction Systems (TJS) used in aircraft electrical installations. It specifies design characteristics and the required type-approval, production and quality tests for modular feed-through and feed-back junctions, grounding modules, in-line splices and associated tracks, brackets and contacts. This part is intended to be read in conjunction with ISO 8668-1 (general characteristics) and ISO 8668-2 (tests).

Key topics and technical requirements

• System components and sizes: Defines modular components (feed-back, feed-through, grounding modules, junction splices, tracks and mounting brackets) and five module/contact sizes: 22D, 22, 20, 16 and 12.
• Contacts and crimping:
  • Male (pin) crimp-removable contacts and integral female (socket) contacts in modules.
  • Male contacts to be gold‑plated minimum 1.27 µm over a non‑silver underplate.
  • Crimp barrels sized for specified conductor gauges; tooling indentors and gauging provided (figures in the standard).
  • Crimp tensile strength requirements referenced and augmented from ISO 1966.
• Environmental and mechanical requirements:
  • Temperature class: −65 °C to +200 °C (per ISO 8668‑1 class 3).
  • Integral grommets and sealing plugs to provide moisture seals; finished wire diameter ranges specified for each module size.
  • Oversize-pin protection, anti-rotation features and ability to remove individual modules from tracks.
• Type approval and production tests:
  • Type-approval test program and sample selection rules (family approval by similarity).
  • Specific tests include oversize-pin, contact durability (100 cycles of insertion/extraction), probe damage (bending moment probe), resistance to fluids (per ISO 7137/DO‑160 procedures) and visual/workmanship checks.
  • Production acceptance and ongoing quality tests to ensure conformity.

Practical applications and users

ISO 8668-5 is used where reliable, serviceable, environment‑proof junctions are required in aircraft wiring systems. Typical users:

• Aircraft electrical system designers and OEMs specifying terminal junction systems.
• Wiring harness and connector manufacturers producing TJS modules and crimp contacts.
• Certification and qualification engineers preparing type-approval test plans.
• Quality, production and maintenance engineers applying production acceptance and in-service inspection criteria.

Related standards

• ISO 8668-1 - Terminal junction systems: Characteristics
• ISO 8668-2 - Terminal junction systems: Tests
• ISO 1966 - Crimped joints for aircraft electrical cables
• ISO 7137 - Environmental conditions and test procedures for airborne equipment (fluids/DO‑160 endorsement)
• IEC 512-8 - Electromechanical components: connector mechanical tests

Keywords: ISO 8668-5, terminal junction systems, aircraft connectors, Type 3 system, crimp contacts, module sizes, type approval tests, production tests, aerospace wiring.