GPU Preventive Maintenance Guide

Ground Power Cables (GPCs) – Aviation Ground Support Equipment #

1. Introduction #

Ground Power Cables (GPCs) are critical components of the Ground Power Unit (GPU) system used to supply aircraft with electrical power while on the ground. Preventive maintenance ensures cable safety, electrical integrity, and compliance with aviation standards.

While this guide provides general preventive maintenance recommendations, it is the user’s responsibility to ensure proper inspection, handling, and compliance with local safety regulations.

2. Purpose #

To establish systematic maintenance procedures that ensure GPCs are safe, functional, and conform to applicable aviation standards. GPU connection wear and tear will vary from location to location based on usage, weather conditions, damage and other factors. Therefore, it is imperative that cables are inspected on a periodic basis and repaired or replaced once the cable shows excessive wear, corrosion of contacts, misuse, evidence of water intrusion, pose a safety risk or have sustained any damage. Beyond the inspections mentioned above it is also important to test the pins retention capabilities to ensure proper fit and the continued safe and efficient use of the connection.

The associate operating the connection is the first line of detection for any potential anomalies to the cable or connector and should inspect the cable and connection head before plugging the connection into the aircraft.

3. Scope #

This manual applies to cables sold by Anderson Airmotive, SAGE Parts, PAGE GSE, Aero Specialties and TLD (“Alvest Companies”). It is a general guide to inspecting cables and determining when to seek guidance for damaged cables.

4. Definitions #

• GPC: Ground Power Cable
• GPU: Ground Power/Frequency Converter Unit
• Connector: End fitting that interfaces with aircraft
• Visual Inspection: Examination by sight for signs of damage
• Continuity Test: Electrical test to verify cable integrity
• Insulation Resistance Test: Verifies cable insulation quality
• PM: Preventive Maintenance

5. Personnel Requirements #

• Only trained and certified GSE technicians may perform maintenance tasks.
• Personnel must wear appropriate PPE (e.g., gloves, eye protection, safety boots) during all inspection, testing, and handling operations. Additional PPE may be required depending on the working environment and local safety regulations.
• Failure to comply with PPE requirements may result in serious injury and shall release the manufacturer from any resulting liability.

6. Maintenance Schedule #

7. Maintenance Procedures #

7.1 Daily/Weekly Inspection #

• Visually inspect the entire length of cable for:
  • Cuts, bulges, abrasions, cracks, or kinks
  • Connecter damage or loose contact
  • Signs of overheating or melting
  • Check for FOD
• Inspect connector for damage or loose contact
• Check for signs of overheating or melting
• Check for FOD (Foreign Object Debris)
• Check strain reliefs and sheathing
• Ensure connectors are clean and dry
• Replace the cable if insulation is degraded, damaged beyond repair, or fails test.

Action: Tag and remove damaged cable from service.

7.2 Monthly Maintenance #

• Check for correct coiling/storing practices.
• Check for FOD.
• Replace the cable if insulation is degraded, damaged beyond repair, or fails test
• Continuity Test
• Insulation Resistance Test
• Check contact retention force.
• Inspect for corrosion/exposed copper on pins/contacts.
• Replace the cable if insulation is degraded, damaged beyond repair, or fails test

Action: Tag and remove damaged cable from service.

7.4 Quarterly Load Testing #

• Check with a temperature sensor for excessive heating areas on cable and on contact.
• Inspect aircraft side connect per AS81790 spec.
• Replace the cable if insulation is degraded, damaged beyond repair, or fails test
• Check for FOD

Action: Tag and remove damaged cable from service.

7.5 Annual Overhaul #

• Replace cable if insulation is degraded, damaged beyond repair, or fails test.
• Calibrate test equipment.
• Update maintenance records.
• Review procedures and technician certification.
• Replace the cable if insulation is degraded, damaged beyond repair, or fails test.

Action: Tag and remove damaged cable from service.

8. Suggested Cable Storage Guidelines #

• Store cables to avoid sharp bends or tight coils
• Protect from oil and UV exposure
• Use protective caps for cable connecter head where applicable

9. Tools and Equipment #

• P400 Kit with:
  • P2861 Phase Sequence Tester Voltage and phase checker with test point to read no load voltage
  • P471 Pin Gauge Tester 400Hz plug retention tester with lanyard
  • P472 Go/No Go Gauge Aircraft receptacle pin tester with non-metallic handle.
  • P473 Tensionometer Digital inch pound scale with peak reading for power and control plug removal force.
  • P474 IR Thermometer Infrared Digital Thermometer in Fahrenheit.
  • 400Hz Power Pin Bore Brush Nylon socket cleaning bore brush.
  • 400Hz Control Pin Bore Brush Nylon socket cleaning bore brush.
  • Ruggedized Hard Case 16”L x 13”W x 8”H. Include cutout foam to hold above listed components.
• Load bank or test plug
• Protective connector caps
• PPE (Personal Protective Equipment)

10. Documentation and Records #

• Log all inspections, findings, and corrective actions
• Maintain test result sheets (continuity/IR/load)
• Report persistent issues to Engineering/QA

11. Safety Precautions #

• Ensure cable is De-energized before inspection
• Ensure cable is de-energized before mating/un-mated
• Never operate a damaged or questionable cable assembly
• Follow lockout/tagout (LOTO) procedures when applicable

12. References #

• AS7974
• SAE AIR4365
• Any applicable local or national regulations

13. Disclaimer #

This guide is provided for informational purposes only. Each Alvest Company disclaim any liability for direct, indirect, incidental, or consequential damages resulting from the use, improper maintenance, or mishandling of the cables. The end user is solely responsible for inspecting, maintaining, and operating the cables in accordance with the recommendations outlined in this guide and all relevant documentation provided by the manufacturer.
Use of our cables outside the specified conditions, environmental requirements, or recommended procedures outlined herein is at the user’s sole risk. Failure to adhere to these guidelines may result in product failure, safety hazards, and forfeiture of any warranty coverage.

Appendix A #

Photo examples of conditions requiring corrective action:

Contact discoloration

Connector head excessive wear

Excessive Wear and Exposed Contacts