Proper inspection should include a thorough investigation of the aircraft. In particular, the interior of an aircraft fuel tank requires intense scrutiny and attention to detail. Tanks must be checked for multiple discrepancies to include:
- Fuel leakage
- Fuel quantity probe replacement
- Fuel boost pump obstructions
- Faulty wiring
- Structural damage to wings (cracks and corrosion)
- Sealant deterioration
To properly perform inspections and maintenance, technicians must physically crawl inside of the tank if accessible. Most tanks are not large enough for an average sized man to maneuver within easily. For example, the largest fuel tank of a DC-9 measures approximately 2-1/2 feet high, 4-1/2 feet wide and 4-1/2 feet long and are usually smaller on many corporate aircraft.
Due to the hazards of working in such confined spaces, OSHA regulations are in place to protect technicians that are required to perform tank repair as part of their daily duties.
Additionally, maintenance technicians face multiple dangers while performing fuel systems inspections and repairs. Furthermore, jet fuel and other chemicals used internally within the tanks may also contain toxins or irritants that can have adverse affects to the central nervous system.
To protect technicians from these types of hazards, specialized training and procedures are in place.
Before a maintenance technician can safely enter an tank, several critical steps included below must be performed:
- Electrically ground and defuel the aircraft
- Gather and stand by with properly functioning fire protection equipment
- Deactivate associated aircraft systems as required
- Ensure proper ventilation, by applying the proven recommended ventilation techniques
- Frequently monitoring the air quality within the tanks
Portable gas detectors are used to monitor the oxygen and flammable vapor concentrations within the tanks. Oxygen concentrations should be between 19.5 and 23.5 percent. Levels below 19.5 percent are considered oxygen deficient, while levels above 23.5 percent will significantly increase the risk of fire and/or explosion. Monitoring these numbers is critical to the safety of the maintenance crew.
Proper training of the maintenance crew is an important component to conducting proper aircraft fuel tank repairs without an incident. These technicians must maintain constant and accurate voice communication and continuously monitor the aircraft fuel tanks and their surroundings'. All technicians must understand the many critical components within the aircraft fuel tanks, to prevent injury to personnel and costly damage to the aircraft.
Emergency Response Plan
The unfortunate reality of aircraft fuel systems maintenance is that potentially severe issues can occur. The interior of a fuel tank can be a particularly hazardous environment. Therefore, all aircraft service and maintenance procedures should also include an emergency response plan.
Appropriate training is critical to ensuring the safety of flight. Aircraft fuel systems maintenance is an intricate procedure and requires significant monitoring to ensure the safety of all involved. Proper training and effective processes will support a healthy work environment for fuel tank repair technicians by recognizing hazards and having proper protocols in place to respond to any issues that may arise.