Air Force tackles aging aircraft issue head on

  • Published
  • By Darren Heusel
  • Oklahoma City Air Logistics Center Public Affairs
B-52 Stratofortress System Program Office officials here met with Boeing and Defense Department experts to discuss an aging aircraft issue that not only impacts the B-52, but possibly the entire Air Force fleet.

People from Boeing, the Navy, Air Force Research Laboratory, Air Force Materiel Command, the Defense Energy Support Center and experts here attended the fuel tank topcoat peeling conference here recently.

"The purpose of topcoat is for corrosion protection," said Rex Cash, B-52 fuels engineer here. "For the B-52 to remain in service another 40 years, it needs the corrosion protecting benefit of a topcoat in the integral tanks."

This is an important issue "I hope everyone involved will continue working to resolve," said Richard Martin, B-52 deputy SPO director. "FTTP may be presently isolated to only one or two weapon systems, but all aging systems may someday encounter this phenomenon."

The conference highlighted a number of issues associated with FTTP including funding, costs and technical challenges.

"Essentially what we have is an aging aircraft problem," Cash said. "For many years, we've been working a great number of issues to keep the B-52 operational for another 40 years. FTTP is one of the more recent examples of the challenging aging aircraft issues we face, and the innovation and ingenuity necessary to resolve them."

Fuel tank topcoat peeling is not a new issue for the B-52 community. It was first discovered in 1995, leading maintainers to assess any potential affects it could have to the weapon system. It appeared to be a small localized problem in the fuel tanks.

The problem grew recently when maintainers at a forward-operating location reported an increase in failed boost pumps due to a higher operations tempo.

To date, Cash said maintainers have noticed the topcoat wrinkling, peeling and flaking in integral tanks on 53 of the fleet's 94 aircraft, according to reports from both PDM and field experts. The results of these reports indicate that the amount of peeling varies from aircraft to aircraft, but Cash said recent conclusions drawn from data collected during wingtip-to-wingtip programmed depot maintenance inspections suggest all B-52 aircraft will eventually be affected.

Fuel tank topcoat peeling was first discovered on the B-52 during PDM at about the same time most aircraft made the conversion from JP-4 to JP-8 fuel.

"We thought it was more than coincidence that it first appeared so soon after the conversion from JP-4 to JP-8," Cash said. "Almost from the beginning, we suspected FTTP was somehow related to the conversion."

While JP-8 seems to be a major contributor, the conversion to other fuel additives could also be adding to the problem.

Since 1995, Cash said FTTP has also been found on other aging aircraft such as the KC-135 Stratotanker and the Navy's P-3 Orion and the problem could be Defense Department-wide.

"If what we believe is true -- that age, fuel and fuel additives are playing a role in this problem -- these factors are common to all aircraft types and, therefore, other aircraft have the potential for FTTP," he said.

With the B-52 playing a major role in the war on terrorism, more fuel is being run through the boost pumps during a few weeks' time than maintainers would normally see in a year. Since the contamination is more frequent, additional man-hours are being expended to control FTTP by routinely cleaning the boost pump screens and repairing them in the field.

The increase in peeling may mean a greater potential for corrosion, a situation the B-52 team wants to avoid.

A long-term solution, Cash said, would be to remove the old topcoat from the entire B-52 fleet and replace it with a new one. However, he said researchers must first positively identify the cause, devise removal and replacement methods and find a topcoat replacement that meets Air Force standards.

When the B-52 was first constructed in the early-1960s, a topcoat was placed on the integral fuel tanks before they were put together. Removing the old topcoat and replacing it with a new one represents a number of obstacles, with the most challenging being the confined spaces, he said.

Cash said B-52 engineers here are involved in a $12 million study expected to take up to three years to complete. A modification of this magnitude is also estimated to take up to 20,000 man-hours to complete, when the normal PDM cycle for the B-52 is 30,000 man-hours.

"I've worked in the B-52 fuels area since 1991 and of all the problems I've been involved in, I think this is going to be the most challenging," he said. "It certainly could be the most expensive fuel system project I've worked on. That's one of the challenges of this project.

"Using the technology currently available to us, this could be a very expensive project, particularly in the production phase," Cash said. "So, we are exploring various new and emerging technologies to bring the cost down. This is where we have to be innovative and ingenious."

Cash said effective procedures are in place to allow safe operation of the B-52 without operational restrictions. In the meantime, maintainers here will continue to monitor FTTP progression through PDM inspections while a final solution is being developed. (Courtesy of Air Force Materiel Command News Service)