This technical report describes the F-15 programmed depot maintenance (PDM) process as performed at the Warner Robins Air Logistics Center (WR-ALC) in FYs 2004-2006. The average WR-ALC F-15 PDM visit runs behind schedule and lasts about four months. Also, PDM can wait a long time for parts; aircraft move through PDM steps out of sequence, with missing parts catching up with the aircraft when they become available, or cannibalize other aircraft.

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.

This monograph describes a model for evaluating the combined capacity of organic (U.S. Air Force owned and operated) and contractor maintenance assets to meet aircraft programmed depot maintenance (PDM) workloads. The PDM Capacity Assessment Tool (PDMCAT) forecasts the average number of aircraft that will be in PDM status each year over several decades, based on the initial number of aircraft in PDM status, the physical capacity of the facility or facilities (number of docks available for conducting PDM work), the PDM induction policy (the period allowed between the completion of one PDM and the start of the next), and the minimum hands-on flow time (the minimum time it would take a facility to complete a PDM if only one aircraft were in PDM status). While not directly part of the model, the derived induction data can be used to estimate both near- and long-term obligation authority requirements for different induction policies, labor rates, and workload forecasts. To illustrate the model's operations and capabilities, we applied the model to evaluate the U.S. Air Force's current capacity for supporting KC-135 PDM and examined several options for improving both near- and long-term availability. In the process, we discovered that, while future annual fleet costs increase and availability decreases with age and workload, they do so rather less rapidly because the aircraft induction rates (the number of aircraft inducted each year) decrease as the PDM flow time increases. This leads to a less-drastic cost and availability forecast than usual.

RAND Project AIR FORCE'S long term interest in the topic of aging aircraft was rekindled in 1994, when we participated in the Air Force Scientific Advisory Board Summer Study that raised technical concerns about the viability of retaining certain aircraft past their original design lives. In 1997, the National Research Council's report on aging USAF aircraft reinforced those concerns. At that time, we initiated a modest Air Force sponsored research effort focused on emerging technical challenges for aircraft maintenance activities. Last summer we built on that technical background to examine the potential effects that aging aircraft would have on the costs of programmed depot maintenance (PDM) and engine support. The results of that work are documented in the annotated briefing that has been made available to the subcommittee. This year, we have broadened our review to cover other support and modernization activities where aircraft age may affect costs and readiness.

RAND Project AIR FORCE'S long term interest in the topic of aging aircraft was rekindled in 1994, when we participated in the Air Force Scientific Advisory Board Summer Study that raised technical concerns about the viability of retaining certain aircraft past their original design lives. In 1997, the National Research Council's report on aging USAF aircraft reinforced those concerns. At that time, we initiated a modest Air Force sponsored research effort focused on emerging technical challenges for aircraft maintenance activities. Last summer we built on that technical background to examine the potential effects that aging aircraft would have on the costs of programmed depot maintenance (PDM) and engine support. The results of that work are documented in the annotated briefing that has been made available to the subcommittee. This year, we have broadened our review to cover other support and modernization activities where aircraft age may affect costs and readiness.

Part of a larger RAND Project Air Force study on capability-based programming, this report introduces a revealed preference methodology to estimate the value to the United States Air Force of expediting F-15 fighter jet programmed depot maintenance (PDM). Such a valuation estimate would be useful in depot-level cost-benefit analysis. The authors rely on the fact that the Air Force has chosen to pay for intermittent PDM on F-15s to assert that F-15s must have enough value after PDM visits to justify PDM costs. Air Force expenditure data suggest that a typical fiscal year 2005 PDM visit cost about $3.2 million. Using the aircraft valuation curves consistent with PDM being worthwhile, the authors find that expediting an F-15's last PDM visit by a month must be worth at least $60,000. However, using a plausible annual aircraft valuation decline rate, they find that expediting an old F-15's last PDM visit by a month would be worth around $75,000, while expediting a new F-15's first PDM visit by a month would be worth more than $180,000. This report also explores various robustness enhancements. Consideration of aging aircraft issues, for instance, tends to increase the estimated value of expedited PDM.

This technical paper documents the final results of an analysis of the task environment under which depot maintenance technicians perform their jobs--specifically, programmed depot maintenance (PDM) for F-15 aircraft. This effort has resulted in a detailed system-level analysis of PDM activities in which an understanding of the PDM process, specific major jobs with the process, and the types of support necessary for successful job completion have been identified. The motivation for this research was to identify activities in the process that would most benefit from technologies expected from the Integrated Technical Information for the Air Logistics Center (ITI-ALC) Program.