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Faulty hardware forces C-130 inspections

Jud Fiebiger, 560th AMXS Chief C-130 Production swing shift superintendent, points out the upper wing rainbow fitting, where Robins workers found cracked nuts on C-130H tail # 86 0418. U. S. Air Force photo by Sue Sapp

Jud Fiebiger, 560th AMXS Chief C-130 Production swing shift superintendent, points out the upper wing rainbow fitting, where Robins workers found cracked nuts on C-130H tail # 86 0418. U. S. Air Force photo by Sue Sapp

C-130H tail # 86 0418 sits in the hangar after Robins workers found cracks in nuts in the area of the aircraft where the wings connect to the centerbox.  U. S. Air Force photo by Sue Sapp

C-130H tail # 86 0418 sits in the hangar after Robins workers found cracks in nuts in the area of the aircraft where the wings connect to the centerbox. U. S. Air Force photo by Sue Sapp

ROBINS AIR FORCE BASE, Ga. -- Members of the 330th Aircraft Sustainment Group have been working around the clock to keep the C-130 fleet flying after maintainers here discovered defective wing-joint barrel nuts.

On March 1, maintainers at Robins were performing routine maintenance on a C-130H when they discovered that five of the upper 13 barrel nuts were cracked. Terrence May, director of the 330th Aircraft Sustainment Group, said one or two cracked nuts would not be considered a critical problem, but more than two is a concern.

On March 4, Air Force Materiel Command issued an order for the immediate inspection of wing-joint barrel nuts on all C-130 aircraft. Within three days, more than two-thirds of the Air Force fleet of nearly 600 aircraft had been inspected, and more than 40 percent of those had been returned to flight.

Mr. May said in an interview Wednesday that 90 percent of the fleet had been inspected and about half of those were found to have defective nuts.

Supplies of replacement nuts have been shipped to the area of responsibility in Iraq and Afghanistan. Mr. May expected that by Sunday, all of the replacement nuts needed in the U.S. Central Command AOR will be shipped.

Making the replacement on all the planes worldwide, including foreign military services, may take a few more weeks due to the limited supply of the replacement nuts, Mr. May said.

The 330th ASG has set up a 24-hour hotline so that maintainers around the world can call for assistance in making the inspection. Although it has been a hectic few days, Mr. May said, he has been pleased with the response.

"The thing I can't emphasize enough is the professionalism of everyone involved, from the mechanics and maintainers who discovered the issue and speedily brought it to the attention of engineers, to the engineers walking through a disciplined process to look at it, and then the work with the field units to identify field impacts and help us help them in terms of defining how we can minimize the impact to the warfighter," Mr. May said.

To make all of the replacements as quickly as possible, Mr. May said Team Robins members are looking at other nuts already in the supply chain that might make a sufficient replacement. He also said that manufacturing nuts at Robins is a possibility in order to expedite the process.

The cause of the cracks appears to be hydrogen embrittlement, in which high-strength steel can become brittle after being exposed to hydrogen. All of the defective nuts come from a single manufacturer, Mr. May said, but he said that doesn't mean there was a manufacturing defect. The manufacturer could have made the nuts exactly according to specifications.

"It may very well be those nuts were fully manufactured in accordance with the design and we are just finding something a little bit different," he said.

Five separate manufacturers have made the same nut for the C-130s, Mr. May said.

The C-130 outer wing is attached to the center wing with 28 bolts and barrel nuts, with 13 upper and 15 lower on each side of the aircraft. The lower wing nuts are not affected.