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Insights on Aircraft Programmed Depot Maintenance: An Analysis of F-15 PDM

Abstract : This technical report describes the F-15 programmed depot maintenance (PDM) process as it was performed at the Warner Robins Air Logistics Center (WR-ALC) in the FY 2004 through FY 2006 time frame. The F-15 is an all-weather, extremely maneuverable tactical fighter designed to permit the Air Force to gain and maintain superiority in aerial combat. F-15s are on a 6-year PDM cycle (i.e., they are to return for PDM within 6 years of completion of a visit). WR-ALC has a sequential process that F-15s follow when undergoing PDM. Fuselage and wing work are, however, performed in parallel. The mean WR-ALC F-15 PDM visit completed in FY 2006 lasted 119.8 days. This total was down from 130.3 days in FY 2005 but similar to FY 2003 (123.1 days) and FY 2004 (117.5 days) mean durations. In FYs 2002 and 2003, the vast majority of WR-ALC F-15s completed PDM behind schedule. This problem was reduced in recent years, largely because planned durations became more realistic (i.e., longer). In FY 2006, the median F-15 was picked up 8 days after WR-ALC completed work. Pickup lags for F-15s based overseas are expected, because they are typically flown overseas in pairs to make more efficient use of aerial tanker refueling. However, even for continental United States (CONUS) based aircraft, it was not uncommon for operators to wait a week or more to retrieve their completed F-15s. There is considerable variation in how much time aircraft spend at specific steps or cells in the F-15 PDM process. WR-ALC is concerned about part issues. The PDM line does not have a particularly high priority, so it can wait considerable periods for parts. One symptom of and adaptation to part problems is "traveling work" (i.e., having an aircraft move forward through WR-ALC's cellular flow without all the tasks prescribed in a cell being completed). When the missing part is obtained, the part catches up with the aircraft and is installed. Another symptom of and adaptation to part problems is cannibalization.