More than 100 C-130 Hercules cargo aircraft have been temporarily removed from service after cracks were discovered during routine maintenance, Air Mobility Command (AMC) announced Thursday.
Gen. Maryanne Miller, head of AMC, ordered 123 of the 450 C-130 models on Air Force flight lines to be stood down as a safety precaution after "atypical cracks were discovered on the lower center wing joint," also known as the rainbow fitting, according to a news release.
The planes will receive an "immediate time compliance technical order inspection to identify and correct any cracking to ensure airworthiness of these C-130 aircraft," the release states.
The order applies to C-130H and J-model aircraft "that have not received the extended service life center wing box and have greater than 15,000 equivalent flight hours," it adds.
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"There are 96 H and 36 J variants impacted," AMC spokesman Col. Damien Pickart told Military.com in an email.
Pickart explained that 123 are actively being used on the flight line. Another eight aircraft were already in depot; one is in the boneyard.
"AMC also took the measure to alert our sister services and partner nations that fly the C-130 and shared our findings and the [technical order] details," he added.
Rainbow fittings provide structural support within the wings. Over the last few years, fatigue cracks have been common in the wing's center structure.
The Air Force currently flies H and J models; the C-130E was retired in 2012.
If cracking is identified during each plane's eight-hour inspection, a "depot-level replacement of the rainbow fitting will be required," the release states.
If maintainers determine a C-130 shows no cracking, that aircraft "will be immediately returned to service," officials said.
Miller said the temporary removal would not "impact ongoing C-130 support to overseas contingency operations."
Earlier this year, the Air Force took 60 C-130H model aircraft out of service to examine and replace engine propeller blades that inspectors deemed risky because the blades were manufactured before 1971. Many were removed as a safety precaution.
That propeller change was prompted by a Marine Corps KC-130T crash that killed 15 Marines and one Navy corpsman in 2017. A corroded propeller blade -- improperly maintained by Air Force maintenance crews in 2011 and later overlooked by the Navy, according to officials -- set off a series of events that would result in the aircraft coming apart in three pieces before it fell to the ground July 10, 2017, in Leflore County, Mississippi, field, killing all on board.
Following the crash, the Air Force commissioned an "independent review team" to assess the blade overhaul process, ultimately creating a new 21-step inspection process.