Strategic Airlift: Improvements in C-5 Mission Capability Can Help Meet Airlift Requirements
Published: 1995-11-20T00:00:00

Fast Facts:

Highlights:
section_title: Why GAO Did This Study
paragraphs: Pursuant to a congressional request, GAO reviewed the reliability and mission capability of C-5 aircraft and the Department of Defense's (DOD) plan for modifying C-5 aircraft.
section_title: What GAO Found
paragraphs: GAO found that: (1) DOD is relying on C-5 aircraft to deliver about half of the wartime cargo carried by military aircraft, but C-5 mission-capable rates have fallen short of the Air Force's goal and those of other aircraft, because of a lack of spare parts and the complexity and poor reliability of the C-5; (2) the Air Force could improve the C-5 mission capable rate by conducting a readiness evaluation similar to the one it completed for B-1B aircraft and by giving a higher priority to certain C-5 modernization initiatives; (3) the Air Force has not prioritized proposed C-5 modifications and decisionmakers have not fully assessed the impact that these proposed improvements would have on overall aircraft mission capability; and (4) if peacetime C-5 mission capable rates were raised to the Air Force's goal, DOD could better meet its airlift requirements.

section_title: Letter
paragraphs: Under the new national military strategy, the Department of Defense (DOD) must be capable of rapidly deploying armed forces to respond to contingency and humanitarian operations around the world. Military strategic airlift aircraft provide the capability to fly the critical, early arriving troops and cargo for overseas deployments. Since DOD is increasingly relying on the C-5 aircraft as its primary airlifter, we assessed the reliability and mission capability of the aircraft and DOD’s current plan for modifying the C-5.
This review was requested by the Honorable Earl Hutto, former Chairman, Subcommittee on Readiness, House Committee on Armed Services. We are addressing this report to you as the current Chairman of the House Subcommittee on Military Readiness.
subsections: section_title: Background
paragraphs: The Air Force’s Air Mobility Command (AMC) has 104 C-5, 199 C-141, and 16 C-17 strategic airlift aircraft in its fleet. It also has 54 KC-10 and 448 KC-135 tanker aircraft, which can carry cargo. The C-5 aircraft, the largest airlifter, can carry 73 troops and 36 standard cargo pallets or outsize cargo, such as tanks and helicopters. The Air Force received its C-5A models from 1969 to 1973 and its C-5B models from 1986 to 1989. The C-5B model incorporates over 100 reliability and maintainability changes from the previous model and has substantially higher mission capable rates.
The C-5 has been used more than planned since Operation Desert Storm in response to various contingencies as well as shortages of C-141 aircraft and delays in C-17 deliveries. AMC developed a plan to guide the modernization of the C-5 aircraft into the next century and help ensure that the C-5 remains a viable mobility asset. AMC officials believe this modernization effort is important to address concerns regarding the aging aircraft and improve the aircraft’s reliability and maintainability.
In addition to being a major command of the Air Force, AMC is a component of the U.S. Transportation Command, a unified command that provides air, land, and sea transportation for DOD. As a component, AMC is responsible for providing global airlift services and air refueling operations. AMC developed a mission capability rate goal for the C-5 fleet of 75 percent, which means that C-5s must be able to perform one of their major missions 75 percent of the time. Mission capability is a standard used on all military aircraft that allows for easier comparisons among aircraft. Although Air Force planners count on increasing aircraft mission availability in wartime by adding more maintenance personnel and deferring some maintenance inspections, little can be done to increase the spare parts initially available for each plane. Peacetime mission capability rates, especially as they are affected by adequate spare parts availability, are therefore good predictors of likely wartime aircraft mission capability. AMC currently estimates that C-5 aircraft can attain a 14.6 million ton miles per day airlift capability, which would represent almost one-half of the Air Force’s total military aircraft airlift capacity.
section_title: Mission Capable Rates Are Below Standard
paragraphs: Mission capable rates for AMC C-5 aircraft averaged just under 68 percent from July 1994 to June 1995. These rates have been declining since Operation Desert Storm, when AMC achieved mission capable rates of 75 percent or higher. In addition, the C-5 mission capable rates were considerably below comparable airlift and tanker aircraft during the same period, as shown in table 1.1. For example, AMC C-5 mission capable rates averaged over 5 percentage points below those of the troubled C-141 aircraft, which is gradually being retired. Factors accounting for the relatively poorer C-5 mission capable rates included inadequate spare parts support, higher complexity associated with a large aircraft, and the generally poorer reliability characteristics of the older C-5A model aircraft.
subsections: section_title: Lack of Spares Affects Mission Capable Rate
paragraphs: C-5 aircraft are classified as not mission capable when they are either undergoing maintenance or lack spare parts. Between 25 and 50 percent of all not mission capable problems in recent years have been due to a lack of spare parts, as shown in figure 1.1.
AMC has established a goal that the total not mission capable supply (TNMCS) rate should not exceed 7 percent for its operational C-5 fleet. Although the TNMCS rate has shown some improvement in the last few years, it still remains considerably above AMC’s goal, as shown in figure 1.2.
Air Force officials said that the C-5 has historically not received enough spare parts primarily because spare parts procurement was budgeted and allocated based on the number of programmed flying hours. Also, the Air Force funds C-5 spares based on a projected 12.6-percent TNMCS rate. Since the C-5 has been exceeding the number of planned flying hours each year, fleetwide TNMCS rates have been even higher than 12.6 percent; in fiscal year 1994, for example, the rate was about 16.5 percent.
Air Force personnel are sometimes able to work around spare parts shortages by taking parts from one aircraft and using them for another (referred to as cannibalization). According to a recent C-5 Program Management Review, cannibalization tends to decrease the life expectancy of aircraft systems and consumes vast amounts of labor that could better be employed elsewhere. AMC’s goal is one cannibalization action a month per aircraft. Figure 1.3 shows that AMC C-5 aircraft cannibalization actions have remained at a level well above the AMC standard for several years.
To address the spare parts problem, the Air Force changed its calculation method for fiscal year 1994 to recognize that the C-5 has been flying more than its number of programmed hours. Also, for fiscal year 1994, the Air Force allowed some high-priority weapon systems, such as the C-5, to receive more spare parts funding than lower priority systems. These changes may have partly accounted for the improved TNMCS rate during fiscal year 1995. However, neither change had helped improve the cannibalization rate.
For fiscal year 1996, the Air Force has proposed raising C-5 spares funding to a level designed to achieve a 7.5-percent TNMCS rate rather than the current 12.6-percent goal. Air Force officials expect raising the spares support level will add about $4.6 million to annual C-5 spares costs.
section_title: A Readiness Evaluation Could Lead to Higher C-5 Mission Capability Rates
paragraphs: The C-5’s mission capability rates could increase if the Air Force were to conduct a readiness evaluation similar to the operational readiness assessment conducted for B-1B bomber aircraft. That assessment, conducted by the Secretary of the Air Force at the direction of the 1994 National Defense Authorization Act, was to determine if the B-1B could sustain a 75-percent readiness rate, about 18 percentage points higher than it was achieving at that time. The Air Force Operational Test and Evaluation Center (AFOTEC) was enlisted as an independent agent to direct the test and report on the assessment activities. An AFOTEC official estimated the total costs of conducting the assessment was about $2.2 million.
During the B-1B operational assessment, AFOTEC used the results from a test wing to project that the B-1B fleet could achieve mission capable rates of 75 percent by better managing spare parts repair cycles and making better use of existing spares with few new assets. AFOTEC also found that these changes would increase annual program funding by $11 million to $12 million over and above funds already committed for various improvements, initiatives, and spare parts. AFOTEC’s findings were evaluated by the DOD Operational Test and Evaluation Agency as well as by us. Both evaluations supported AFOTEC’s conclusions.
After the assessment was completed, the test wing’s mission capable rate rose to 84 percent, and the entire fleet mission capable rate rose to 66 percent. According to the DOD Operational Test and Evaluation Agency, the primary reason the mission capable rate increased was better spares support—that is, more spares available at the test location and faster turnaround at the intermediate or depot levels. Leadership attention and the significance of the test were important motivating factors, but the mission capable rate could not have been raised without spare parts improvements. Maintenance downtime was reduced when spares were immediately available, and more spares lessened the chance that parts would have to be cannibalized.
One of the major factors accounting for better B-1B spare parts support was the use of the Distribution and Repair in Variable Environments (DRIVE) model. DRIVE manages repair requirements by prioritizing repairs based on their effect on mission capable rates. Current systems, including the one used for the C-5, prioritize repairs based only on the amount of time the part has been in the repair process. In addition, a 1992 Rand report advocated using the DRIVE model to emphasize the effect of repairs on mission capability rather than relying on more traditional indicators.The Air Force mandated use of the DRIVE system at its depots in January 1994, but the system has not yet been implemented by the San Antonio Air Logistics Center, the C-5 depot.
Although the C-5 and B-1B are different aircraft with different missions, we believe a C-5 readiness evaluation could yield similar results to those experienced during the B-1B evaluation. For example, both aircraft have had historically low mission capable rates and poor spare parts support. Also, before the B-1B test, Air Force officials did not think the mission capable rate for the B-1B could be raised nearly as high as the evaluation later demonstrated. However, the officials are now projecting a fleetwide increase in B-1B mission capable rates of 15 percentage points. Air Force airlift officials have stated that improvements to the spares process would have little impact on C-5 mission capability. However, we think improvements similar to the B-1B spare parts process changes could be applied to the C-5 spares process as well.
Officials from the C-5 manufacturer stated that improving the C-5 spares process by analyzing parts that most affect mission capable rates, similar to the DRIVE model philosophy, and improving the spare parts pipeline could result in a 40-percent reduction in TNMCS rates. That reduction would increase the mission capable rate fleetwide by about 6.6 percentage points. An increase of this magnitude would give DOD an additional 1.3 million ton miles a day of cargo-carrying capability—the equivalent of 10 C-17 aircraft.
AMC officials identified several difficulties in reducing TNMCS rates for the C-5 aircraft by 40 percent. Officials noted that the practical requirement to maintain an aircraft at each of the two active bases for cannibalization constitutes a significant portion of the TNMCS rate. They further noted that aircraft undergoing refurbishment or unit inspections also contribute to the TNMCS rate. Notwithstanding this position, we note that if AMC achieved its 7-percent TNMCS goal, it would have accomplished about a 40-percent reduction in the TNMCS rate—which C-5 manufacturer officials projected.
section_title: C-5 Modernization Plan Needs Reprioritization
paragraphs: AMC established a C-5 modernization plan to increase mission capability rates and reduce personnel requirements and life-cycle costs. According to AMC officials, modification initiatives are generally prioritized based on potential reliability and maintainability improvements to the aircraft as well as cost. The resulting priorities are later modified and updated by various reviewing officials. AMC’s top 10 proposed modifications, at the time of our review, and our estimate of their impact on mission capability, are shown in table 1.2. Many of these modifications will not be funded until at least the year 2000 and completed several years after that.
Even though we were able to calculate potential mission capable rate increases for each of the top priority modifications, AMC has not analyzed how much the modifications would contribute to increasing mission capability. Until AMC does that analysis, decisionmakers cannot consider the impact that the proposed improvements could have on mission capability or total airlift capability. Also, if AMC considered mission capability increases as a key factor in prioritizing planned C-5 modifications, the current order of priorities would most likely change. However, we recognize that AMC might have to consider other factors, such as safety considerations, when it prioritizes modifications.
We identified the 10th-priority modification—hydraulic valve replacement—as being relatively low in cost but having the most potential for increasing aircraft mission capability. Failures associated with the C-5’s hydraulic system are one of the leading causes of reliability problems. The hydraulic valve replacement is designed to eliminate surges when opening selector valves on the landing gear, cargo doors, and ramps. Because this modification was only recently identified as one of the top 10 priorities, it has not been scheduled for funding. However, AMC estimated that the modification could be funded as early as fiscal year 1997.
The C-5 manufacturer estimates that failures in hydraulic system plumbing, mounting fixtures, and components should decrease by two-thirds to three-fourths when the hydraulic valve modification is completed. More importantly, the 1.1-percentage point potential increase in C-5 mission capability resulting from the modification would provide DOD with an additional 0.18 million ton miles per day of cargo-carrying capability—equating to 1.4 C-17 aircraft.
In comparison, the two top priority modifications—autopilot replacement and engine turbine improvement—would likely only increase mission capability a little at a relatively large cost. Other high-priority efforts, such as floor corrosion prevention and courier compartment flooring, are improvements that would not result in any potential increase in aircraft mission capability.
DOD has not been providing adequate funding to meet the original schedule for proposed C-5 improvements. For example, two major upgrades to improve the C-5’s reliability, the malfunction detection analysis and recording system and the main landing gear actuator, were first identified in fiscal year 1985 and scheduled to be completed by fiscal year 1994. However, funding delays have stretched these modifications by 4 years to fiscal year 1998. According to our 1992 report, one of the major factors contributing to the C-141’s recent severe problems was inadequate funding to implement necessary modifications. AMC stated in its 1995 Air Mobility Master Plan that not completing scheduled improvements would degrade capability and increase operating costs.
section_title: Recommendations
paragraphs: We recommend that the Secretary of Defense direct the Secretary of the Air Force to (1) conduct a readiness evaluation to determine how C-5 peacetime mission capability can be improved and the costs of such improvements and (2) assess the impact of proposed aircraft modifications on C-5 mission capability and then reprioritize the proposals according to the results of the assessment.
We also recommend that the Secretary direct the Commander in Chief, U.S. Transportation Command, to include in strategic mobility planning the potential increase in airlift cargo capability made possible by a higher C-5 mission capable rate.
section_title: Agency Comments and Our Evaluation
paragraphs: DOD partially concurred with our report (see app. I). DOD stated that it has initiated some actions that would satisfy the intent of our recommendation that the Air Force conduct a readiness evaluation. These actions include conducting a 1994 logistics demonstration project to improve and streamline the C-5 management structure and policies for handling spare parts and repairing components, as well as incorporating lessons learned from the B-1B operational readiness assessment to better manage the C-5 program. Although these actions are good first steps, DOD must ensure that they are fully implemented. In particular, DOD needs to use the DRIVE model, which was successfully demonstrated during the B-1B assessment, to allocate C-5 spare parts and prioritize their repair.
DOD agreed with our recommendation that the Air Force assess the impact of proposed aircraft modifications on mission capability and reprioritize the modifications accordingly. DOD noted that the San Antonio Air Logistics Center was developing a computer model that will be able to quantify the effects of proposed aircraft reliability improvements on mission capability. DOD expects this model, scheduled for completion in July 1996, to help improve the method for prioritizing C-5 modifications.
DOD did not agree with our recommendation that the Transportation Command’s strategic mobility planning include the potential increase in C-5 cargo capability resulting from a higher mission capable rate. DOD stated that the potential cargo capability increase would not translate directly into increases in cargo delivered to a theater of conflict because of the limited airfield infrastructure (including ramp space, refueling facilities, and material handling equipment).
Although potential increases in cargo capability identified in our report may not translate directly into cargo delivered to the theater under some scenarios, the potential capability still exists under more unconstrained scenarios with many available airfields or fields with areas large enough to accommodate substantial numbers of C-5 aircraft. To maximize potential C-5 cargo deliveries, DOD should consider using C-5 aircraft in the more unconstrained scenarios. DOD bases many of its conclusions about a more capable C-5 aircraft on studies of buying additional quantities of a new C-5D aircraft, which has not yet been developed. These conclusions could be substantially different if DOD looked at current quantities of more capable existing C-5A and C-5B aircraft. Therefore, we continue to believe DOD should consider the implications of more capable existing C-5 aircraft in its modeling efforts and decisions on the mix of future aircraft.
section_title: Scope and Methodology
paragraphs: We conducted our review at AMC, Scott Air Force Base, Illinois; 436th Airlift Wing, Dover Air Force Base, Delaware; C-5 System Program Director’s Office, San Antonio Air Logistics Center, Kelly Air Force Base, Texas; Lockheed Aeronautical Systems Company, Marietta, Georgia; and Air Force Headquarters, Washington, D.C. We interviewed various officials at these locations and reviewed pertinent regulations, guidance, and reports pertaining to the subject areas. We also interviewed officials regarding the B-1B readiness assessment and DRIVE model at the Air Force Operational Test and Evaluation Center, Kirtland Air Force Base, New Mexico; Air Combat Command Headquarters, Langley Air Force Base, Virginia; and Air Force Materiel Command, Wright-Patterson Air Force Base, Ohio.
To calculate potential aircraft availability and mission capability increases, we relied on Air Force and C-5 manufacturer estimates of increases in mission capable hours attributable to the proposed changes. We added the mission capable hours attributable to those improvements to the 1994 total fleet mission capable hours and calculated a revised mission capable rate. We used the revised mission capable rate to calculate a new aircraft utilization rate, which we used to recalculate a C-5 million ton mile per day cargo contribution. We divided increases in the C-5 cargo contribution by the currently estimated AMC million ton mile per day contribution of a C-17 to determine the equivalent number of C-17s.
We conducted our review from August 1994 to August 1995 in accordance with generally accepted government auditing standards.
We are sending copies of this report to the Ranking Minority Member of your Subcommittee and the Chairmen and Ranking Minority Members of the Senate Committee on Armed Services, House Committee on National Security, and Senate and House Committees on Appropriations; the Secretaries of Defense, the Army, the Air Force, and the Navy; the Commandant of the Marine Corps; the Commander in Chief, U.S. Transportation Command; and the Director, Office of Management and Budget.
If you or your staff have any questions concerning this report, please contact me at (202) 512-5140. The major contributors to this report are listed in appendix II.
section_title: Comments From the Department of Defense
paragraphs: The following is our comment on the Department of Defense’s (DOD) letter dated October 23, 1995.
subsections: section_title: GAO Comment
paragraphs: 1. DOD stated that it could not substantiate the additional 1.3 million ton miles per day of capability that we reported the C-5 aircraft could provide. Our calculation was based on the 40-percent improvement in total not mission capable supply (TNMCS) rate projected by the C-5 manufacturer. We discussed how we calculated utilization rates and million ton mile contributions in the Scope and Methodology section. We used standard Air Mobility Command (AMC) formulas in those calculations. In addition, as noted in the report, if AMC met its own 7-percent goal for TNMCS, it could achieve the 40-percent TNMCS reduction projected by the C-5 manufacturer.
section_title: Major Contributors to This Report
subsections: section_title: National Security and International Affairs Division, Washington, D.C.
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