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

A deployed JEIM for the TF-34 requires 3.5 C-5 equivalents to meet requirements. The options in which repair takes place in CONUS require an average of .25 C-5 equivalents weekly throughout the MTW. The options in which repair takes place at an FSL require an average of three C-130 equivalents weekly throughout the MTW. Total transportation resources needed for these options are only slightly higher than those needed for the DepJEIM and are concentrated after the first month when airlift is more available.

Dealing with Uncertainty

The previous analyses assume relatively fixed-removal rates, repair and ENMCS times, spare levels, and sortie rates with values, in most cases, corresponding to current experience. These values will not always be fixed. Different scenarios may require different flying profiles. Removal rates may change. As a result, the effects of changes in some of these variables were explored.

Transportation

Transportation assumptions may be the most critical and subject to the most contention, particularly as the Air Force uses more joint transportation and defense agencies expand transportation contracts with private carriers. Figure 4 shows how transportation time affects missed sorties in an FSL repair structure for the F100-229. If the one-way transportation time is 2 days or less, as assumed, sorties missed because of transportation delays are negligible. For each additional day required for transportation, however, missed sorties increase, especially for the F-15 unit.

Figure 5 shows similar effects for the home-base repair performance for the F100-229. If transportation between FOLs and home exceeds 15 days, missed sorties increase substantially.

TF-34 repair is less sensitive to transportation times because of its low removal rates and different repair structure.

Removal Rate

Removal rates may increase as engines age or decline and as new maintenance practices such as reliability-centered maintenance take effect.

For the F100-229, comparatively few sorties are missed if removal rates remain below ten per 1,000 flying hours or twice that assumed. Figure 6 shows that, at higher removal rates, the FSL alternative continues to perform better than the other alternatives.

To avoid missed sorties, the removal rate for the F100-220 cannot exceed the assumptions by much. In fact, if the removal rate for the F-16 during war remains at its current peacetime level of 7.5 per 1,000, only an FSL JEIM structure will avoid missed sorties. System performance will be worse and missed sorties highest with the DepJEIM.

Even with removal rates substantially lower than those assumed, the DepJEIM cannot perform as well as an FSL structure. Figure 7 shows available spares for the 220 engines on F-15s in an FSL structure with a baseline removal rate of five per 1,000 hours, for a DepJEIM with the baseline rate, and for a DepJEIM with lower removal rates. Even at a removal rate of two per 1,000 engine hours, the DepJEIM performance is worse than that for the baseline FSL case in days 50 to 65 of the MTW. The results for the F-16 are similar; however, only at the lowest removal rates does DepJEIM become competitive with the baseline FSL case.