Complex aircraft require periodic maintenance checks to assess needed repairs for continued vehicle availability. However, such checks are expensive and the associated aircraft downtime can reduce fleet mission effectiveness. The United States Air Force plans to consolidate the time-based (isochronal) C-5 aircraft major inspection activities for eight C-5 home stations into three locations. Isochronal inspections rely on a calendar method to schedule inspections and disregard actual flying hours between inspections. By having the same personnel perform these inspections for all flying units and by adopting commercial aircraft condition-based inspection strategies, the Air Force hopes to gain efficiencies in performing these inspections. Conversely, the site phase-out schedule and reduced number of inspection locations raises questions about whether overall C-5 mission capability will be reduced. These proposed revisions were simulated in a designed experiment to assess the impacts to fleet availability and inspection site workload.
TopIntroduction
Scheduled maintenance is crucial to preserving high aircraft reliability levels. The U.S. Federal Aviation Administration sued Southwest Airlines for over $10 million in 2008, alleging that the airline failed to perform mandatory periodic safety checks and thus flew unsafe aircraft (Griffith & Bronstein, 2008). These mandatory periodic checks—performed by both the commercial sector and the military—are preventive measures designed to reduce the chances of aircraft component failures (Boller, 2001; Bowen, 1996; Kozanidis et al., 2008; Lambert & Troughton, 1967). However, because such inspections are expensive, aircraft maintenance practices are migrating toward condition-based strategies and centralized maintenance processes to preserve aircraft readiness at lower cost (Bolinger, 2007; Durand, 2008; Gellar et al., 2005; Kapoor et al., 2004; Swift, 2008; Wu et al., 2004).
In this paper, we discuss our research to estimate potential improvements the United States Air Force may achieve by changing C-5 transport aircraft inspection processes. The C-5 Galaxy, one of the largest aircraft in the world, provides a strategic airlift capability for the United States Air Force and supports many defense and humanitarian objectives, and thus efforts to increase its operational availability are important. Availability is the percentage of time that an aircraft is deemed as flight-capable; hence aircraft downtime resulting from maintenance or inspections reduces availability and thus decreases overall operational availability.
The Air Force is planning on implementing three important initiatives simultaneously: consolidating existing aircraft inspection sites, using new inspection site-aircraft assignment selection methods, and adopting new aircraft inspection procedures—all in the hope of sustaining C-5 availability levels at less cost. Our simulation modeling and analyses of these initiatives can help the Air Force understand how to best achieve these desired outcomes. Because of the strong similarity between commercial and military aviation maintenance processes, our research method and results are applicable to any aircraft maintenance organization seeking ways to preserve aircraft readiness at lower cost.
This paper is organized as follows: The next section surveys the relevant background and literature. The specific research problem and the methodology employed is also described. We then follow with our analysis. We conclude with recommendations for specific Air Force actions, a note on the study’s limitations, and suggestions for future research.