The Role of Depots in Aircraft Maintenance
When aircraft are operated, they experience stresses that can weaken or break parts and structural components on the aircraft. Even aircraft that are not flown will eventually need maintenance as seals dry and metal corrodes.
Maintenance can occur at different locations or levels. Clearly, it would be most convenient to undertake maintenance at the flight line directly where the aircraft operates. The flight line is the location either at an air base or on a ship where military personnel undertake routine maintenance on the aircraft. Maintenance personnel at flight lines often remove inoperative parts from aircraft and replace them with operating parts (either new or repaired parts).
Some maintenance, however, cannot be undertaken on the flight line. Flightline maintenance personnel may lack the training or skills required or the flight line may lack the requisite equipment or space. If, for instance, an aircraft needs large-scale disassembly to address a problem, that disassembly must be done away from the flight line.
The military services have used different approaches to maintenance behind the flight line. The Navy uses three levels of maintenance. The Navy’s flight-line maintenance is termed organizational maintenance, which is performed by the squadron where the aircraft operates, including on aircraft carriers. The second level, termed intermediate maintenance, is performed by military personnel on aircraft carriers and at shore-based air stations. Intermediate maintenance tasks include calibration, repair, or replacement of damaged or unserviceable parts, components, or assemblies; emergency manufacture of nonavailable parts; and provision of technical assistance to flight-line maintainers (Office of the Assistant Secretary of Defense for Logistics & Materiel Readiness, 2016). If tasks cannot be accomplished in intermediate maintenance, the aircraft is sent to a central Navy depot with yet additional capabilities and equipment. The two Navy depots that have done the most work on F/A-18 A–D variants (termed legacy Hornets) are Fleet Readiness Center (FRC) Southwest at North Island in San Diego, California, and FRC Southeast at Jacksonville, Florida.
The Air Force relies on two levels of maintenance: flight lines and depots. Most F-15 depot-level maintenance occurs at the Warner Robins Air Logistics Center (ALC) at Robins Air Force Base in central Georgia. Most A-10 and F-16 depot-level maintenance occurs at the Ogden ALC at Hill Air Force Base in Utah.