Expeditionary Operations: intermediate engine maintenance alternatives

Air Force Journal of Logistics, Spring, 2001 by Mahyar A. Amouzegar, Lionel Galway, Amanda Geller, Robert S. Tripp, Clifford Grammich

As a result, simulation techniques were used. Engine repair has special characteristics making a simulation model useful for analysis. Sortie requirements change over time, and many measurements such as sorties missed, current spare levels, and queue sizes at key shop points are inherently dynamic. Further, evaluation of alternative systems also requires dynamic analysis of transportation times, capacity, schedules, and management decisions. A simulation model allows analysis of such dynamic variables and how they change during an operation.

Each simulation model is based on the following sequence of events: aircraft are flown from home bases and FOLs to meet peacetime (training) and wartime flying schedules, respectively. After each mission, engines are checked on the flight line, and some maintenance is done. When engines accumulate enough flying hours or when unscheduled maintenance is required, they are removed from the planes and sent to a JEIM facility. Bases and FOLs use spare engines to replace those sent to intermediate maintenance but can miss some daily required sorties if not enough engines are available to meet demands.

In the intermediate shop, engines wait in a repair queue until space and labor are available. Once parts and labor are available, JEIM personnel repair the engines. The labor and physical equipment to work on an engine comprise a rail team. [3] The model also accounts for delays in receiving parts that may render an engine not mission capable due to supply (ENMCS).

After repair, the engine is reassembled and flows to a queue for the test cells. After testing, it is moved to final inspection and then returned to the flight line where it is available as a serviceable spare that can be installed on aircraft as needed.

The model makes some further modifications to simulate wartime demand and need. It allows deployed aircraft to fly at rates that vary daily, assumes wartime work hours, and gives priority to deployed units.

The model uses data from the Comprehensive Engine Management System and the Reliability and Maintainability Management Information System and from interviews with personnel at a number of units.

Assessing Repair by Engine Type

For each of the engines examined, intermediate maintenance performance during a single major theater war (MTW) scenario was simulated. The focus was on wartime demand because each structure in peacetime must include the excess capacity needed for war.

F100 Engine Analysis

The F100 series engine is divided into several modules that are designed to be interchanged in the field and can be repaired separately. This article presents results from the analysis of F100-229 and F100-220 engines. The F100-229 is the newest version of the F100 and comprises a rather small fleet. The F100-220 preceded the 229, entering service in the 1980s; this fleet has more than 1,200 engines.

The model for the F100 engines simulates 2 years of operations, with a single MTW beginning after 1 year of peace and ending in 100 days, after which all units return to their home bases and resume a peacetime flying schedule. Resources needed to give equal performance, as measured by missed sorties, are used to compare JEIM alternatives.