Among them, he said, were corrosion, skin weakness, frayed electrical wiring, and unanticipated component failures.

With KC-135 tankers in depot, he noted, “you can peel the skin layers apart, and powder comes out the middle.” F-15 fighters were operating under flight restrictions imposed after failures in which tails actually snapped off the aircraft.

Staff photo by Guy Aceto

In the case of the A-10, the Air Force was finding more structural defects than anyone expected. Time spent repairing the attack aircraft ballooned.

The need for modernization was so urgent, said Jumper last February, that “it is difficult to set priorities.” He added, “All of this comes together to make us question how we judge the airworthiness of our aircraft.”

Compounding the problem was the fact that USAF had no independent and systematic way to judge the health of these aged aircraft. It needed a way to evaluate return on investment—to determine whether it made sense to keep repairing old aircraft or dump them and procure brand-new ones.

Part of the answer, announced Jumper, was creation of an “airworthiness” board “to verify and to certify” that aged aircraft could and should remain in use. Today, the Air Force’s out-of-production fleets are still a problem, but the service now has a system in place to determine what to do about it.

Fleet Viability Board

The airworthiness board is now called the Fleet Viability Board (FVB), and its work has already had a major impact on how the Air Force looks at aged aircraft. The existence of an independent board means USAF leaders receive recommendations free of bias.

The board assesses aged aircraft without bowing to pressure from competing views. Warfighting commanders might want to keep a system in service because it is too important to live without. Conversely, maintainers at the depots may believe that an aircraft is no longer worth the time and money required to keep it flying.

The board idea was suggested by James G. Roche, Secretary of the Air Force. Roche, who is a retired Navy captain, was inspired by the example of the Navy’s Board of Inspection and Survey. As Roche told Congress, he wanted to provide a “dedicated set of professionals who will develop objective criteria for retiring aircraft from the operational fleet.”

Until recently, the Air Force lacked a systematic way to evaluate the fleet-wide health of aged aircraft. The Fleet Viability Board changes that and will give USAF an unbiased appraisal of the health of aircraft such as these elderly B-52s. (USAF photo by Michael Dey)

Until then, there had been no unbiased way to look at the overall health of a fleet. “While there have been some ad hoc fleet studies in the past, they centered on some narrow issues,” such as the cost of corrosion in a specific aircraft, said Col. Francis P. Crowley, FVB director at Wright-Patterson AFB, Ohio.

The old system was no longer tenable. Brig. Gen. P. David Gillett Jr., USAF maintenance director on the Air Staff, warned, “We are in uncharted waters” with respect to the age of aircraft, and it is harder than ever to predict the effects of this age. He said that maintenance demands have steadily grown because of increasing structural, wiring, and mechanical failures attributable to maturity.

Over all, Gillett said, aircraft maintenance hours per flying hour have increased by 31 percent since 1991, and the cost per flying hour has risen 13 percent since 1999. “We are still able to perform when called upon, but at increasing cost,” he said. Crowley said that the new board is “more comprehensive in scope because we assess the availability of a fleet,” the health of subsystems, and the continued cost of ownership.

If the FVB determines that an aircraft, as currently configured, will not meet requirements in the future, the board will declare that aircraft not viable, “unless the Air Force funds additional upgrades,” Crowley said. This is what happened with the board’s first completed assessment.

The FVB took on the C-5A Galaxy airlift aircraft as its first order of business this year. By July the board had reached two conclusions—first, that the C-5A, the oldest of the C-5 fleet, is worth keeping in service, provided it receives a series of upgrades, and, second, that the C-5A, even with these upgrades, will never be as effective as the Air Force would like it to be.

After analyzing the C-5A, the board turned its attention to a set of older KC-135Es, tankers that posed a safety risk in flight. The board is now evaluating the health of the entire Stratotanker fleet.

Next will come a hard look at the Air Force’s fleet of A-10 attack aircraft. Future studies will focus on older F-16s (Blocks 10 and 15) and the B-52H bomber.

Officials explained that aircraft are selected for a viability review based on many factors. These include how near a system is to the end of its expected service life, its mission capable rates, number of maintenance hours required per flying hour, and its cannibalization rate.

Gillett said “structural integrity” is the most critical factor in determining viability assessment priorities.

The FVB has no decision-making power on its own. It gives recommendations to Jumper and Roche, who use the suggestions for making force structure and modernization decisions. The board looks at cost, aircraft availability, and “operational health” as the leading indicators of a fleet’s long-term viability.

The first order of business was a look at the C-5A. The FVB determined that the C-5A is worth keeping in service, but only if it receives a series of engine and avionics upgrades. (USAF photo by Sue Sapp)

Assessments project snapshots of an aircraft’s operational cost and overall health six, 14, and 25 years into the future. The board noted that it “leaves consideration of force structure or operational impact to the Air Force corporate structure.”

C-5A: $22 Billion Needed

The FVB’s C-5A assessment looked at the 60 A-models scheduled to remain in service. (Ignored were 14 others slated to retire by the end of 2005.)

The aircraft were built in the 1968-73 period, and the FVB report noted that, in the 1970s, they had “abysmal” mission capable rates of about 40 percent. Reliability has slowly but steadily increased to an MC rate of about 55 percent today. In contrast, the Air Force’s C-5Bs, which are half as old as the A models, posted MC rates better than 72 percent in 2002 and 2003. The C-5A is never expected to achieve that level of reliability.

Over the next 25 years, the Air Force may spend more than $22 billion (calculated in 2000 dollars) to support the C-5A, the report noted. The board deemed this investment worthwhile and issued some surprising findings.

For instance, it said that the C-5A operations and support costs, though the highest for all transport aircraft, “are not out of line with other large aircraft.”

The C-5A performs a valuable mission, and there is a shortage of airlift capability, but, if the planned avionics and engine upgrades do not take place, “the cost of maintenance will continue to accelerate, and reliability ... will continue to degrade,” the board determined.

Corrosion and airframe fatigue will not become factors in the long-term health of the C-5A for at least another 25 years, in the view of the FVB. “We did not see the structural issues on the C-5A most people expected us to find on an aging fleet,” Crowley said.

The Air Force will have a better understanding of the aircraft’s structural health once it completes a C-5A teardown and analysis at Warner Robins Air Logistics Center in Georgia. During the teardown, officials are looking at engine pylon attachments, bulkheads, and other components in a search for unexpected structural problems. The teardown analysis should be complete at the end of 2005.

If the C-5A receives planned avionics and engine improvements—and a second avionics upgrade around 2020—it will remain viable through at least 2029, when it would reach 45,000 flight hours, the board determined. Without these upgrades, explained one official, it makes the most sense to simply retire the aircraft and get the needed lift capability some other way.

Structural integrity and operational availability are key factors in determining which aircraft will be evaluated. Here, SSgt. Donovan Osborne, 57th Aircraft Maintenance Sq., Nellis AFB, Nev., checks for cracks in an F-15E engine. (USAF photo by SSgt. Chrissy Fitzgerald)

Planned C-5A improvements include an avionics modernization program (AMP) and a reliability enhancement and re-engining program (RERP). These two efforts will bring “significant improvement” in reliability, maintainability, and capability, according to the FVB.

AMP and RERP will “mostly” solve mission limitations, the board's final report said.

“Even with the substantial benefits of these modifications, the fleet will fall short of mission capability and availability goals throughout the remaining life of the system,” said the board.

The Air Force’s target MC rate for the C-5A is 75 percent. “We were surprised to discover that, while these modifications will be quite beneficial, the C-5A’s mission capable rate will never achieve” that 75 percent goal, Crowley told Air Force Magazine.

The board projects that the AMP and RERP will gradually improve C-5A reliability to a 60 percent MC rate in 2013. The rate will eventually peak at 71 percent in 2020. Without AMP and RERP, “the aircraft will not meet planned Global Air Traffic Management emissions or noise requirements,” which would limit where the Galaxys can be flown, said Crowley.

Engines Are Key

Most future reliability and performance improvements are contingent upon the re-engining program. The C-5A’s existing TF39 engines “will not provide the necessary performance to meet future GATM climb and cruise performance [or] emission compliance requirements,” the C-5A report stated. Propulsion system dependability and performance will vastly improve as RERP is implemented, the board determined.

First, a “windfall” of TF39 engines will become available as those engines come off of C-5Bs, beginning in 2006. Later, the A models should also receive “more reliable, maintainable, and better performing” engines, starting in 2013.

Many re-engining details remain uncertain. The Air Force sent out the first C-5B for RERP modifications just this October, and that aircraft is not scheduled to fly with its new power plants for a year. And the number of C-5s to be re-engined has not been determined. US Transportation Command is currently conducting a new mobility requirements study.

The avionics upgrade yields a much smaller reliability improvement, but is operationally critical. C-5A avionics are “incapable of meeting current and future GATM requirements” and offer “little to no growth capability,” the report stated. Without AMP, mission restrictions are likely, and even with the modernization, an additional “tech refresh” will be needed around 2020.

As a safety precaution, USAF recently grounded 29 KC-135Es with old engine struts. The FVB is now looking at the entire KC-135 fleet. KC-135Rs, such as this one, are expected to be in better shape. (USAF photo by SrA. Joshua Strang)

The board noted that these estimates are, ultimately, projections. If the estimates are conservative, the fleet could exceed the 75 percent MC rate goal from Fiscal 2018 through 2029. If, however, the estimates are optimistic, “this will greatly exasperate an already poor availability position,” the board wrote.

Gen. John W. Handy, commander of US Transportation Command and Air Mobility Command, found the FVB’s C-5A review useful but perhaps misdirected. Handy told defense reporters in July that he would have preferred an “as-is” assessment.

“To me, the determination of viability is to take a baseline weapon system and say it’s viable over time, without modification,” Handy said. “You can sustain almost anything over time if you spend enough money to keep it viable. ... They answered the question, but I’m not sure the question was stated correctly,” he said.

Gillett said the board’s recommendation was that the C-5A modifications are worth performing. In the case of the C-5A, the board found AMP and RERP will result in flat cost growth and improved availability. The board therefore declared the C-5A “viable”—with the upgrades.

It is now up to USAF’s corporate leadership and the warfighting commanders to decide if they agree.

Gillett said the board would declare an aircraft “not viable” if major upgrades would still result in an aircraft with declining mission capable rates, poor performance, or “inability to meet mission requirements.”

Handy noted that AMC can compare upgraded C-5As with “other ways to get the job done,” but making long-term predictions about aged aircraft can be unsettling.

“It’s the ‘ifs’ that really worry me in there,” he said of the report. “We have not executed the AMP mod on schedule. We’re not on schedule with the RERP. ... [This is] the reality of the budgeting process and competing demands.”

KC-135E: Unsafe Corrosion

In September, the Air Force announced that Handy had ordered that 29 KC-135Es be “removed from the flying schedule.”

These Stratotankers were among 30 the FVB had inspected, tail by tail, to validate a no-fly recommendation from the KC-135 System Program Office. When the viability board concurred, and briefed Handy on its findings, he ordered 29 with corroded engine mounts to stay on the ground.

By Oct. 1, officials said, it was decided that the 29 troublesome tankers would not be permitted to fly again until their corroded engine pylon support struts were repaired. “This decision is based on flight safety considerations,” officials said in a release.

Crowley explained, “The most significant finding from the KC-135E special assessment is that the thermal heating and corrosion damage to the engine pylon support struts on unrepaired aircraft is more severe” than previously thought.

Gillett said these 30 KC-135s were “originally programmed for retirement” in 2005 and had not received upgrades along with the KC-135Es scheduled to remain in service. (One of the 30 had already received strut repairs, in conjunction with other maintenance, and was judged still safe to fly.) The aircraft cannot be retired for the time being because Congress has prohibited the Air Force from doing so until the details of a new tanker acquisition plan are worked out.

Crowley said the “special assessment” of the 30 tankers will be used to “kick start” the full KC-135 review, which should be completed in April 2005. The full review will look at all 546 aircraft in the KC-135 fleet—including remaining Es and newer R models.

The FVB follows a standing review process, but particulars of each aircraft require assessments with “considerable fine-tuning,” Crowley said. For example, the engine-mount struts that were the primary concern on the first 30 KC-135Es are not expected to be a problem for KC-135Rs, which have newer engines and struts.

A-10s and Beyond

After the tankers, the FVB will turn its attention to the A-10 Warthog, an aircraft that has been heavily tasked in both Afghanistan and Iraq.

“I would not want to retire any of these airplanes if they weren’t approaching a service life issue, because we need them,” said Gen. Hal M. Hornburg, Air Combat Command chief.

The FVB will soon evaluate the A-10. Structural improvements are planned, but the number of airframes to be retained is unknown. Here, mechanics with the 51st Maintenance Sq., Osan AB, South Korea, look for damage. (USAF photo by MSgt. Val Gempis)

However, Hornburg predicted that it will simply be too difficult for the Air Force to keep all A-10s in service. This is an aged aircraft problem, not a financial problem, he said.

The A-10, which first flew in 1975, is currently undergoing a service life extension program to replace deteriorating wing skins and other structural components. The A-10 fleet will also receive a precision engagement upgrade, to allow it to carry precision weapons.

Speaking to reporters in September, Hornburg said ACC “will probably still want to retire some [A-10s] because it won’t be worthwhile to modernize airplanes that ... [are] just about to go off the end of the cliff with respect to their service life. In other words, at some point, with any airplane, you cross a line of diminishing returns.”

The FVB will identify that point of diminishing marginal returns. The board will assess ACC’s service life estimates and determine if there are technological breakthroughs that can “extend the service life or whether the service life needs to come back to the left,” Hornburg said.

After the A-10, two other aircraft with long-term structural issues are on the FVB’s docket.

Older F-16s are now completing the Falcon Star structural upgrade program, but the fighters are subject to extreme airframe stress every time they go into combat or on realistic training missions. The B-52, meanwhile, is thought to have a solid airframe, but the aged bomber is expected to remain in service for decades, and many of its parts have long been out of production.