KC-46 mishaps’ reports released

You may remember a bit back when an F-15 had an unfortunate mid-air refueling experience with one of our new KC-46 tankers (the ones supposed to replace the aging 707-based KC-135 and KC-10 tankers.) At the time it was speculated that the boom had malfunctioned and caused the accident. The boom literally fell off the tanker into the desert

In an unusual disclosure, the Air Force released accident reports for all three mishaps together, with a single press release.

After an early morning take-off from Travis Air Force Base, California, on Aug. 21, 2024, the Kansas-based KC-46 met with two F-15Es for a routine mid-air refueling. One of the jets tried four times to hook up to the plane’s refueling boom, but the fighter’s pilot had trouble maintaining constant contact. His wingman connected for a full gas-up.

On a final attempt, as the boom connected to the F-15E’s fuel port, the fighter continued to fly towards the tanker, compressing the boom to 3.75 feet, more than two feet shorter than its normal operation. Then, as the two jets tried to separate, the boom momentarily caught in the F-15E’s fuel port. As the F-15 eased back, it pulled on the stuck probe with 7,404 pounds of force, extending the boom 17 feet.

In the few seconds the jet was stuck, the boom operator tried to fly the boom upwards. When the probe finally released from the F-15, the upward push from the boom operator caused the boom to spring violently upwards, smashing into the bottom of the KC-46’s tail section.

“The boom reached a peak fly-up rate of 114 degrees per second,” the report found, before smashing into the underside of the tanker.

The damage, officials said, totaled $14,381,303.

Yeah, that’s an owie. And only the most recent of three.

On Oct. 15, 2022, a KC-46 from Joint Base McGuire-Dix-Lakehurst flew a routine training mission to refuel a flight of F-15Es from Seymour Johnson Air Force Base, North Carolina.

Similar to the 2024 accident, the boom’s nozzle became stuck in the F-15 after a mistake by the boom operator and the failure of the F-15E pilot to recognize the condition. Also, like the 2024 accident, when the boom finally released, the operator’s actions caused the boom to spring upwards forcefully and strike the underside of the KC-46, causing over $8 million in damage.

You may also recall that the KC-46 does away with the rear boom operator’s position, and has a remote camera array for the boom operator  to use.

In that 2022 flight, an accident board found, the boom operator “inadvertently placed a radial force on the ARB that caused the nozzle to become bound in the receiver’s receptacle. As a result, the bound forces exceeded the structural limitations” of the boom and “caused a rapid upward movement” that struck the plane.

But unlike the 2024 mishap, the accident board found the operator’s mistakes were neither intentional nor preventable, but were due to a poorly designed flight control system, or FCS.

“A pattern begins to emerge which leads me to conclude that this FCS input by [the boom operator] was inadvertent and due to a limitation of the KC-46 [boom] control system,” investigation board President Col. Chad Cisewski wrote. “It is not a reasonable conclusion that [the boom operator] could have recognized his inadvertent input and corrected the situation with the current [boom] control deficiencies.”   Task & Purpose

The third incident was minor, when it was found the RSV cameras had inadequate resolution to see if the boom was engaged properly – that only cost a bit over $100,000

It’s sounding like there is plenty of blame to go around between design, boom operators, and refuelee pilots.

Category: Air Force