Most combat aircraft systems today utilize three levels of repair capability; organizational, intermediate, and depot. This is referred to as three-level maintenance. The relative difficulty of the repair action typically increases from the organizational level through the intermediate and depot levels. Most of the time, \"flight line\" and minor repair actions are classified as organizational level repairs. These include removing and replacing line replaceable units (LRUs) and accomplishing minor repairs on the aircraft. Intermediate level, or off-equipment maintenance, require special equipment and more personnel proficiency than organizational level repairs. Intermediate level repairs include performing tests on LRUs and accomplishing needed repairs through the removal and replacement of faulty components called shop replaceable units (SRUs). Repair shop technicians conduct fault isolation procedures with test equipment to identify faulty components. If the repair of the LRU is beyond the capability of the intermediate repair shop then the asset is declared to be not repairable this station (NRTS) and is shipped to the Air Logistics Center (depot) for repair. The depot level of maintenance repair typically requires specific industrial capabilities for component overhauls or major modifications. | Intermediate Aircraft Maintenance by Jeoffrey D Sloan, Paperback | Indigo Chapters