ISO 1967:1974

Overview

ISO 1967:1974 specifies the physical and electrical sizing requirements for aircraft fire-resisting electrical cables with single copper conductors. The standard covers cables intended for use at a nominal voltage of 600 V and a maximum frequency of 2000 Hz. It is focused on wiring used in the fire zones of aircraft and establishes limits for dimensions, conductor resistance per unit length and mass per unit length.

Key environmental criteria in the scope include:

• Continuous service temperature not exceeding 280 °C (ambient plus heating).
• Short-term survival at 400 °C for a limited period.
• Retention of a degree of dielectric strength after exposure to a 1100 °C flame for 5 minutes.

The document provides tabulated values for cable diameter, maximum conductor resistance and maximum mass per unit length, allowing designers and manufacturers to select and verify cables suitable for critical aerospace installations.

Key Topics

• Cable dimensions: Standardised outer diameters and conductor cross-sections for single-copper-conductor fire-resisting cables to ensure compatibility and predictable routing in aircraft structures.
• Conductor resistance per unit length: Maximum allowable linear resistance values at specified temperatures to support electrical performance and thermal calculations.
• Mass per unit length: Limits enabling weight estimation and balance calculations important in aerospace design.
• Temperature and flame performance: Criteria for continuous and short-duration high-temperature exposure and residual dielectric capability after flame exposure.
• Intended use: Primarily for installation in aircraft fire zones where fire-resistance and high-temperature endurance are required.

Applications

ISO 1967:1974 is applied where dependable electrical circuits must survive extreme thermal events and maintain critical functions in aircraft. Typical applications include:

• Emergency and essential power circuits routed through designated fire zones.
• Instrumentation and communication cabling that must remain operational during or after a fire event.
• Wiring harnesses on transport and rotorcraft where weight, dimensional control and heat tolerance are critical.

Practical benefits:

• Enables consistent procurement and qualification of cables across suppliers.
• Reduces risk by specifying minimum electrical and mechanical attributes for fire zones.
• Facilitates weight and thermal management in system design.

Related Standards

• ISO 2155 - Aircraft - Fire-resisting electrical cables - Required characteristics (referenced for characteristic definitions).
• ISO 2156 - Aircraft - Fire-resisting electrical cables - Test methods (referenced for test procedures and verification).

For engineers and procurement specialists, ISO 1967:1974 provides a baseline for selecting copper conductor fire-resisting cables for aerospace applications where dimensions, conductor resistance and mass are key design constraints. Always consult the full standard text and referenced documents (ISO 2155, ISO 2156) when verifying compliance and carrying out tests.