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Inside DoD

DoD Releases a Report on the Effects of Corrosion on the Cost and Availability of Air Force Aircraft and Missiles

The Corrosion Prevention and Control Integrated Product Team (CPC IPT) asked LMI Government Consulting in May of 2010 to estimate the impact of corrosion on the availability of all DoD aviation weapon systems and on the cost of Navy, Marine Corps, and Air Force aviation systems. This report presents our estimates of the corrosion-related availability and cost impact for Air Force aircraft and missiles.

Using fiscal year (FY) 2008 and FY2009 as a measurement baseline, we estimated the annual corrosion cost for Air Force aviation and missiles to be $4.5 billion, or 24.0 percent of maintenance costs. We also estimated the effect of corrosion on non-available hours (NAH) for all Air Force aviation assets. Corrosion is a contributing factor in approximately 2.1 million hours of non-availability, or 12.1 percent of the total. These hours equate to an average of 15.9 days of corrosion-related non-availability per year for every aircraft in active status.1

This review of Air Force aviation and missiles is part of a multiple-year plan to measure the impact of corrosion on cost and availability. This is the first availability study. Table 1 lists past and future cost studies, while Table 2 lists the availability studies.

Table 1 - Cost of Corrosion Studies
aStudy period is one calendar year.

Table 2 - Effect of Corrosion on Availability Studies
aStudy period is one calendar year.

To provide a sense of scale for our estimates, the overall aircraft and missile corro-sion-related costs equate to an average of 24 percent of total annual Air Force maintenance costs. This percentage is among the highest in the corrosion cost studies completed thus far. The overall Air Force aviation and missile corrosion cost as a percent of maintenance cost has been steadily increasing over the last four years of the study.

Our estimated corrosion costs apply to 136 types of Air Force aviation equipment and to 25 different engine models. The scope of the study included an inventory of 5,938 aircraft and 9 ballistic missile types for the cost study, and 5,504 aircraft for the availability study. To our knowledge, these data include all Air Force aviation and missile types.

We used three schema groups to categorize corrosion costs associated with aviation and missile equipment. In Figure 1, we show the study results segregated by sche-ma. The percentages indicate the relative ratios of the different schemas.

Figure 1 - Cost of Corrosion for Air Force Aircraft and Missile Equipment by Schema (FY2009 data)
Note: This figure does not depict the $32 million in corrosion costs that we were unable to classify as either preventive or corrective, nor does it depict the $21 million in corrosion costs that we could not assign to structure or parts. DM = depot maintenance; FLM = field-level maintenance; ONR = outside normal reporting.

Schema group 1 shows that corrosion-related depot maintenance (DM) costs exceed corrosion-related field-level maintenance (FLM) costs. This is true both on a total cost and percentage of maintenance basis. Corrosion-related DM costs ($3.025 bil-lion) are more than double the corrosion-related FLM costs ($1.460 billion). Addi-tionally, the DM corrosion cost as a percentage of total DM cost is 27.5 percent, exceeding the FLM corrosion cost as a percentage of total FLM, 19.0 percent, (see Table 3). Together, DM and FLM account for 99 percent of the total combined corrosion cost for Air Force aircraft and missiles ($4.484 billion). Outside normal reporting corrosion costs are minor ($46 million) when compared to those associated with DM and FLM.

Table 3 - Comparison of DM and FLM Corrosion Cost ($ in millions)

Schema group 2 compares corrective costs ($2,443 million, or 55 percent) and preventive costs ($2,010 million, 45 percent). Schema 3 compares structure-related costs ($2,114 million, or 47 percent) to parts-related costs ($2,350 million, or 53 percent). We distributed the $4.5 billion corrosion costs among each schema separately to the extent that we could classify the respective maintenance records by their schema.

We stratified the corrosion costs of Air Force aviation and missile systems by type/model/series (TMS), total cost, and cost per item. We then ranked the top 10 systems by their total corrosion cost and average corrosion cost. The order in which Air Force aviation assets are listed in Table 4 suggests a priority for further examination from a corrosion cost standpoint. The TMS that we highlight are among the top 10 for combined total and average corrosion cost ranking for each of the four study years. The B-52H was the second largest contributor to average corrosion cost for Air Force aviation and the fourth largest in total corrosion cost, making it the greatest contributor from a combined ranking standpoint.

Table 4 - Highest Combined Ranking for Average and Total Corrosion Cost (FY2009)

We measured the total corrosion-related NAH (2,102,476) in a manner consistent with how the Air Force reports its availability results. Corrosion-related NAH account for 12.1 percent of the total reported. We show the highest 10 contributors to corrosion-related NAH in Table 5.

Table 5 - Highest 10 Corrosion Contributors to Total NAH (Non-Available Hours) by TMS (FY2009)

The F-16C fighter has the largest total of corrosion-related NAH; its large fleet size compensates for a relatively low percentage of corrosion-related NAH (11.9 percent). The KC-135R tanker and C-130H transport have the highest corro-sion-related NAH percentages at 20.1 and 21.6.

Preventive maintenance accounts for nearly two-thirds of the total corrosion-related NAH, with inspection being by far the major contributor to corrosion-related total NAH. Table 6 shows a breakdown of the preventive maintenance NAH.

Table 6 - Preventive Corrosion NAH by Activity (FY2009)

We identified an apparent strong relationship between corrosion cost and corrosion-related NAH by aircraft type for the largest corrosion cost aircraft (see Table 7). Three of the top four aircraft types with the largest cost of corrosion also are among the four highest contributors to corrosion-related NAH (some aircraft do not have NAH reported). These aircraft are the KC-135R, C-130H, and F-16C. This relationship between corrosion cost and corrosion-related NAH also holds from a percentage standpoint. If an aircraft has a corrosion cost as a percentage of maintenance cost that is among the highest, then the corrosion NAH as a percentage of total NAH is also among the highest. This finding further suggests that the opposite should also be true: a reduction in the corrosion cost percentage should improve the corrosion-related availability results.

“Multiple aircraft” is a category assigned to those items of repair that are used in different aircraft types. The cost of the repair cannot be assigned to a specific type. Examples include engines, communication systems, and some ground support systems.

Table 7 - Relationship between Total Corrosion Cost and Total NAH
aNAHs are not reported for multiple aircraft, only by serial number and aircraft type.


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