aviation cable factory

What Are the Inspection Procedures for Aviation Cable?

Maintaining the integrity of aircraft wiring is critical for safety and reliability. Aviation cable inspections are systematic processes designed to identify damage, wear, or degradation before they cause failures. Here are the key inspection procedures:

​1. Preparation & Safety First​

• •​Power Down:​​ Ensure the aircraft system is completely powered down and safe for work.
• •​Access:​​ Gain safe access to the wiring harnesses or cables needing inspection.
• •​PPE:​​ Wear appropriate Personal Protective Equipment (PPE) – safety glasses and gloves are essential.
• •​Tools:​​ Gather necessary tools: bright flashlight, inspection mirror, magnifying glass, multimeter, Megohmmeter (Insulation Resistance Tester), cable testers (TDR if applicable), and relevant maintenance manuals.

​2. Visual Inspection (The Primary Method)​​

• •​Look Closely:​​ Examine the entire accessible length of the cable or harness.
• •​Common Damage Points:​​ Pay special attention to areas near connectors, clamps, grommets, areas of flexing, and where cables pass through structures or near hot components.
• •​What to Look For:​​
  • •​Chafing/Abrasion:​​ Worn insulation exposing conductor.
  • •​Cuts/Nicks:​​ Damage to insulation or conductors.
  • •​Pinching/Crushing:​​ Flattened or deformed cables.
  • •​Heat Damage:​​ Melted, hardened, discolored, or charred insulation.
  • •​Corrosion:​​ Green/white powder (copper) or white powder (aluminum) on terminals or conductors. Look for corroded shield braids.
  • •​Broken Strands:​​ Especially near terminals or in flex areas.
  • •​Connector Issues:​​ Bent or broken pins/sockets, cracked inserts, loose backshells, corrosion inside connectors, damaged seals.
  • •​Loose Hardware:​​ Missing, loose, or damaged clamps, tie-wraps (ensure smooth edges), or support hardware.
  • •​Improper Routing:​​ Cables touching sharp edges, hot components (hydraulic lines, engines), or moving parts. Ensure adequate slack and drip loops.
  • •​Contamination:​​ Fluids (oil, hydraulic fluid, Skydrol), dirt, or debris on cables or connectors.

​3. Physical Inspection (Tactile Checks)​​

• •​Feel for Damage:​​ Gently run fingers along the cable (where safe and appropriate). Feel for lumps, stiffness, flat spots, or irregularities that might not be visually obvious.
• •​Check Security:​​ Gently tug on connectors and clamps to ensure they are securely fastened (without applying excessive force).
• •​Check Flexibility:​​ Ensure cables in flexing areas haven’t become stiff or brittle.

​4. Electrical Testing (When Required/Authorized)​​

• •​Continuity Check:​​ Use a multimeter to verify electrical continuity along the conductor(s). Ensures no open circuits.
• •​Insulation Resistance (IR) Test:​​ Use a Megohmmeter to measure resistance between conductors and between conductors and ground/shield. Low resistance indicates insulation breakdown, moisture ingress, or contamination. Must be performed per specific aircraft manual procedures and limits.
• •​Time Domain Reflectometry (TDR):​​ Specialized equipment used to locate the precise distance to faults like opens, shorts, or significant impedance changes along a cable run.
• •​Circuit Functionality:​​ After repairs or if a fault is suspected, functional testing of the specific circuit/system may be necessary.

​5. Documentation & Action​

• •​Record Findings:​​ Document all observations meticulously, including location, type of damage, and severity. Use photos if possible.
• •​Assess:​​ Determine if the damage requires immediate repair, scheduled repair, or is acceptable per the aircraft maintenance manual (AMM) or wiring practices manual (e.g., AS50881).
• •​Repair/Rework:​​ Perform repairs strictly according to approved data (AMM, Component Maintenance Manuals, Standard Practices Manuals). This may involve splicing, terminating, replacing sections, or replacing entire harnesses.
• •​Re-inspect:​​ Visually inspect the repair area after work is complete.
• •​Re-test:​​ Perform necessary electrical tests (Continuity, IR) after repair.

​Common Issues Found & Solutions:​​

• •​Minor Chafing:​​ Apply protective sleeving (e.g., convoluted tubing, abrasion tape) if allowed per manual. Monitor.
• •​Cut Insulation:​​ Requires repair (splice or termination) per approved procedures.
• •​Broken Conductor:​​ Requires repair (splice or termination).
• •​Corroded Terminal:​​ Clean (if permitted) or replace the connector/terminal.
• •​Loose Connector:​​ Secure according to torque specifications.
• •​Contaminated Connector:​​ Clean using approved methods and materials.

​Key Takeaways:​​

• •​Regularity:​​ Inspections should be performed at scheduled intervals (per maintenance program) and whenever damage is suspected.
• •​Thoroughness:​​ Careful visual inspection is the cornerstone. Look everywhere cables run.
• •​Standards:​​ Always follow the specific aircraft manufacturer’s maintenance manuals and approved wiring practices (like FAA AC 25.1701, AS50881).
• •​Qualification:​​ Ensure personnel performing inspections and repairs are properly trained and authorized.
• •​Documentation:​​ Accurate records are crucial for maintenance history and safety.

By following these structured inspection procedures, aviation maintenance professionals can effectively identify and address potential wiring issues, ensuring the continued safe and reliable operation of aircraft systems.