aviation cable factory

How to Test Aviation Cable for Reliability: A Practical Guide

Aviation cable – the lifeline of critical systems from flight controls to essential instruments – must be utterly reliable. Failure isn’t an option thousands of feet in the air. Whether you’re a maintenance engineer, an aircraft builder, or a drone operator, understanding how to verify aviation cable reliability is paramount. This guide breaks down the essential testing methods used by the pros.

Why Reliability Testing is Non-Negotiable:

• ​Safety Critical: Cable failure can lead to catastrophic loss of control or system malfunction.
• ​Harsh Environment: Aircraft experience extreme vibrations, temperature swings, moisture, chemicals, and flexing.
• ​Long Lifespans: Aircraft operate for decades; cables must endure without degradation.
• ​Regulatory Compliance: Strict aviation authorities (FAA, EASA, etc.) mandate rigorous standards.

Key Aviation Cable Reliability Tests:

1. ​Breaking Strength / Tensile Testing:
   • ​Why? Ensures the cable can withstand maximum operational loads plus a significant safety margin.
   • ​How? A controlled pulling force is applied until the cable breaks. Modern test machines pull at constant rates.
   • ​Key Metric: Minimum Breaking Strength (MBS) or Ultimate Tensile Strength (UTS). Must meet or exceed the specification/standard for the cable type and size (e.g., MIL-DTL-83420, AS23053).
2. ​Proof Load Testing:
   • ​Why? Verifies that the cable can handle its maximum rated load safely without permanent deformation.
   • ​How? A load equal to a defined percentage (often 50-60%) of its rated MBS is applied and held for a short duration (e.g., 30 seconds). The cable must not break.
   • ​Key Metric: Successful holding of the proof load without breakage or excessive elongation.
3. ​Flexure (Bending) and Fatigue Testing:
   • ​Why? Simulates real-world movement over pulleys, through fairleads, and in control systems. Assesses resistance to wear and fatigue failure.
   • ​How? Cable is repeatedly bent back and forth over a pulley/sheaveradius under a specified tension (often 10-30% of MBS).
   • ​Key Metric: The number of cycles to failure. Higher cycle counts indicate superior fatigue life. Standards specify the required cycles (e.g., MIL spec bend tests).
4. ​Environmental Testing:
   • ​Why? Ensures cable performance under the extreme conditions aircraft encounter.
   • ​Common Types:
     • ​Temperature Cycling: Cable is exposed to high and low extreme temperatures (-65°F/-54°C to +160°F/+71°C or higher) for multiple cycles. Checks for cracking, hardening, or performance loss.
     • ​Salt Spray (Fog) Testing: Simulates corrosive coastal/sea environments. Cable is exposed to a fine salt mist spray for extended periods (e.g., 24-500+ hours depending on spec). Assesses corrosion resistance of wires and fittings.
     • ​Humidity Testing: Exposes cable to high humidity levels (often 95%+) at elevated temperatures. Checks for insulation degradation, water ingress, and corrosion.
     • ​Fluid Resistance: Immersion in aircraft fluids (hydraulic fluid, fuel, deicing fluid) to check for swelling, softening, or degradation of insulation/jackets.
5. ​Electrical Continuity and Resistance:
   • ​Why? Essential for electrical wiring bundles ensuring signals/power flow correctly.
   • ​How? Using precision multimeters or dedicated testers:
     • ​Continuity: Confirms an unbroken conductive path through the wire or bundle.
     • ​Resistance: Measures the inherent opposition to current flow (DC Resistance).
   • ​Key Metric: Measured resistance must be within specified limits for the wire gauge and length. High resistance indicates potential damage (nicking, corrosion) or undersized wire.
6. ​Non-Destructive Testing (NDT):
   • ​Why? Detect internal or surface defects without destroying the cable. Crucial for inspections.
   • ​Common Methods:
     • ​Visual Inspection: Meticulous examination for kinks, abrasion, corrosion on wires/fittings, cracked insulation, broken strands, deformation. Often using magnifiers or borescopes.
     • ​Magnetic Particle Inspection (MPI): Used for ferrous metal fittings (sockets, thimbles). Detects surface cracks. Magnetically charges the part, applies ferrous particles; particles cluster at crack sites.
     • ​Liquid Penetrant Inspection (LPI): Used for non-ferrous fittings. A colored or fluorescent dye penetrates surface cracks; excess is removed, and a developer makes defects visible.

Ensuring Reliable Test Results:

• ​Adhere to Standards: Testing must follow recognized aviation standards (MIL-specs, SAE AS standards, ASTM, manufacturer specs).
• ​Calibrated Equipment: Testing machines (tensile, fatigue, environmental chambers) and measurement tools (multimeters) must be regularly calibrated for traceable accuracy.
• ​Certified Labs: For critical qualification testing or regulatory submission, use accredited laboratories (e.g., ISO 17025).
• ​Detailed Records: Meticulously document test parameters (load, duration, cycles, temperature), results, and observations for traceability and compliance.