WRIGHT-PATTERSON AIR FORCE BASE, Ohio (AFNS) - An immediate action time compliance technical order was issued by Air Force Materiel Command officials here March 4 to inspect all C-130 Hercules aircraft due to potential cracking of wing-joint barrel nuts.
The time compliance technical order was ordered after a C-130H undergoing routine scheduled maintenance at Warner Robins Air Logistics Center, Ga., was found with five of its upper 13 barrel nuts cracked.
The C-130 outer wing is attached to the center wing with 28 bolts and barrel nuts - 13 upper and 15 lower - on each side of the aircraft. The lower wing barrel nuts are not affected.
The barrel nuts are also used on some C-130 refueling-pod pylons and engine trusses.
Individual C-130 units are conducting the inspections and all suspect nuts are being replaced to ensure the integrity of the aircraft and safety of pilots, passengers and crewmembers.
Within the first three days after the time compliance technical order was issued, more than two-thirds of the Air Force fleet of nearly 600 aircraft had been inspected, and more than 40 percent returned to flight. Priority shipments of replacement barrel nuts are going to C-130 units at forward-deployed locations, and those with special operations and aeromedical missions.
To help make the replacement process easier, members of the 330th Aircraft Sustainment Group at Robins Air Force Base, Ga., have been working around the clock to handle questions and issues from the C-130 community, which includes other U.S. and foreign military services.
The cause of the cracks appears to be hydrogen embrittlement, a process by which various metals, particularly high-strength steel, become brittle and crack after being exposed to hydrogen.