Aging Gracefully

The Air Force Fleet Viability Board is taking a hard look at how long it makes sense to keep older planes in the air.

By Patrick Chisholm

In 1990, the average aircraft in the Air Force’s inventory was 13 years old. A decade from now, the average age will be about 25 years old. Already, 40 percent of the active fleet has been in service at least that long.

One step in coping with the operational and budgetary ramifications of aging platforms has been the establishment of the Air Force Fleet Viability Board (AF FVB). Its mission is to project an aircraft fleet’s viability over 25 years and make objective recommendations to the secretary of the Air Force, Air Force chief of staff and other senior leaders regarding whether specific aircraft should be retired or sustained.

The AF FVB is mainly staffed by the Air Force Aeronautical Systems Center (ASC) at Wright-Patterson Air Force Base, OH, which is responsible for managing aircraft modernization programs. Recognizing that aircraft are in service much longer than their designers originally anticipated, ASC now emphasizes modifications and sustainment, in addition to its original focus on research, development and production.

The main objectives of the AF FVB are to determine the technical health of the aircraft, the cost of continuing to operate and support it, and the portion of the fleet that will be available to perform missions over a projected 25-year period. The board also assesses weapon systems’ operational health, availability, maintenance and depot records, as well as the cost of flying the aircraft.

The AF FVB plans to assess each mission design series in the Air Force and reassess them about every five years.

Burden of Years

Prior to the creation of the board, the Air Force relied on airworthiness and structural integrity programs to assess fleet condition. But it did not have a process for assessing the burden of age-related factors, or for incorporating issues of operational health, aircraft availability and the cost of continued ownership. There was no official process for determining when aircraft should be retired from service.

The Air Force needed an independent group to perform a consistent, repeatable process to standardize the information used to make sustainment or retirement decisions, and to present that information to senior Air Force leaders, as the Navy does in considering ship retirement. So James G. Roche, then the secretary of the Air Force, asked Lieutenant General Michael E. Zettler, then deputy chief of staff for installations and logistics, to establish such a process.

The AF FVB was established in August 2003, when a director was hired to create an assessment process. The AF FVB is not a decision making body, but only makes recommendations.

The AF FVB’s make-up is grouped into three tiers. One tier is the Survey Assessment Team (SAT), which has 13 full-time staff members, including the board director and experts in engineering, logistics and cost analysis. They are mostly provided by ASC.

Another tier is the Senior Board, consisting of seven members who mentor their functional counterparts on the SAT and validate the assessment findings. Along with the board director, members are responsible for systems engineering and propulsion, logistics, cost, structures, avionics and subsystems. They come from the Air Staff and Air Force Materiel Command.

The remaining tier is the Senior Board Advisors, who are non-Air Force aerospace industry experts. Their focus is to determine if the assessment is fair in terms of determining viability in support of the nation’s defense needs.

The aim of this diverse, three-tiered system is to give the Air Force leadership an honest and unbiased assessment of a fleet’s longevity and cost.

“The Senior Board meets about four times during an assessment, and the SAT members are in direct contact with their mentors on a frequent basis,” said Colonel Francis Crowley, AF FVB director. “The advisors validate the draft report based on their technical expertise.”

Operational control lies with the Air Force Installations and Logistics Directorate. The current deputy chief of staff for installations and logistics, Lieutenant General Donald Wetekam, provides overall direction and supervision to the board.

“They provide top-cover to ensure the assessment process remains unbiased and without preordained judgments,” said Crowley. On a day-to-day basis, however, the board works independently.

Passing the Test

An aircraft’s viability is based on its cost, availability and operational health. During a full-fledged assessment of an aircraft, members of the AF FVB query databases, interview key stakeholders and analyze findings, which form the basis of their report. The report includes a 25-year projection of the fleet’s operational health, availability and ownership cost.

The first aircraft to be evaluated by the AF FVB was the C-5A Galaxy cargo aircraft, first deployed in 1970. With an initial mission capability rate at only 42 percent, the aircraft was beset with problems from the outset.

The AF FVB prototype assessment began in October 2003 and was completed in April 2004. The assessment concluded that the C-5A fleet is viable for at least 25 years, provided the avionics and re-engine upgrades are completed as planned and that the aircraft undergoes some engineering changes and an avionics upgrade around 2020.

At 58 percent, the C-5A’s mission capability rate is well below the 75 percent standard. But 58 percent is an improvement from its initial 42 percent rate, thanks to better management in areas such as maintenance, supply and acquisition. An avionics modernization program and a reliability enhancement and re-engine program are expected to boost performance even more. Compared with other large Air Force aircraft, Crowley said, C-5 operational costs are not out of line.

At the beginning of the assessment, 14 C-5As were marked for retirement. One of those is in the process of being completely dissected in an effort to discover obvious or subtle problems. That process will not be complete for another year, but the initial inspection revealed no major flaws.

Currently, the board is completing a special assessment of 30 KC-135E Stratotanker aircraft, which the Air Force has planned to retire in the next two years.

The oldest Air Force aircraft, along with the B-52, the Boeing KC-135 has been around since 1956. About 530 are still in service. The KC-135E arose from a 1982 modification to the KC-135A fleet. Among other things, that modification involved outfitting previous versions of the KC-135 with TF-33-PW-102 Pratt & Whitney engines. Fuel efficiency rose by 14 percent, and 20 percent more fuel could be offloaded.

This special assessment and the follow-on full-fledged KC-135E and R-model assessments will assess viability, but not decide the controversial issue of whether and how the aircraft should be replaced with new tankers. “Although our report may feed into the Air Force corporate process for looking at alternative solutions for mission or capability, we leave that comparison to the analysis of alternatives process,” noted Crowley.

Although the KC-135 has undergone many upgrades, maintenance costs are high. For every hour of flying time, an average of about 16 hours are spent on maintenance. A total of 61 KC-135Es are to be retired through 2006.

After the KC-135 assessments, the next aircraft to be evaluated include three combat aircraft: the A-10, the F-16 Blocks 10 and 15, and the B-52H.

Structural Issues

Even though many types of aircraft have been around for decades, they have been continually retrofitted with improved components and systems. However, the structural members of aircraft remain relatively constant.

“Whether an aircraft can be retrofitted in perpetuity depends on an aircraft’s structural condition and whether it is feasible from the perspective of aircraft availability and cost of continued ownership,” said Crowley. “Simply because it is technically feasible to retrofit an aircraft in perpetuity does not mean it is the best solution for our national defense or treasury needs.”

Aging aircraft problems are most commonly the result of corrosion to the aircraft structure. These include pitting corrosion, crevice corrosion, stress corrosion, cracking and corrosion fatigue. They frequently occur without any outward sign of damage and are usually discovered coincidentally. The Air Force estimates that the costs of direct corrosion are more than $800 million per year.

Another issue concerns the potential problem of diminishing manufacturing sources, where there may be fewer suppliers/parts manufacturers today than previously, making long-term modernization particularly challenging. But based on its assessments, AF FVB has found few examples of a shrinking manufacturing base being a major concern, according to Crowley. An exception to this is the old, unsupportable auxiliary power unit on some KC-135E aircraft.

Regarding the maintenance backlog within the Air Force, Crowley said that, based on the board’s analysis of the C-5A, the long-term mission-capable and depot flow day trends are improving, and the board projects continued improvement based on planned modifications.

“However, this trend may be unique to the C-5A fleet and is not necessarily applicable to other aging fleets,” he said, adding that it is difficult to say in general terms that maintenance backlogs and mission-capable rates are getting better.