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A damaged KC-46 boom is seen after landing following a mishap on Aug. 21, 2024.
The U.S. Air Force on Aug. 25 released three investigations into incidents involving the Boeing KC-46A all linked to a similar issue—the tanker’s stiff boom getting stuck in receiving aircraft.
The “stiff boom” issue has long been a known deficiency on the aircraft, with the boom being redesigned to address the problem. While this has prevented the KC-46 from refueling the relatively slow-moving A-10, the investigations show it has also caused problems with faster fighters.
The first incident occurred Oct. 15, 2022, involving a KC-46 from the 2nd Air Refueling Squadron at Joint Base McGuire-Dix-Lakehurst, New Jersey, and an F-15E from the 4th Fighter Wing at Seymour-Johnson AFB, North Carolina.
During the sortie, the refueling boom’s nozzle became bound in the F-15E during a breakaway, causing the boom to strike the tail of the KC-46 when it broke away. The KC-46 and boom were damaged at a cost of $8.3 million.
An investigation found that a limitation of the boom’s control system caused the operator to inadvertently place a radial force on the nozzle, which caused it to be bound in the receptacle. The limitation of the control system led the boom to go into an uncontrollable state during the upward motion toward the aircraft.
Additionally, investigators determined the receiving F-15E didn’t consider the KC-46’s stiff boom characteristics, which call for significantly more aft-fore thrust input to move the boom telescope in and out while in contact.
The second mishap involved the same KC-46 squadron and an F-22 from the 94th Fighter Squadron at Joint Base Langley-Eustis, Virginia. During the Nov. 7, 2022, flight, there was another nozzle-binding incident during a breakaway with the F-22 that damaged the nozzle beyond repair. The cost of the damage was $103,295.
The investigation found the boom operator failed to verify if the nozzle was clear of the receptacle prior to making control inputs. Manual inputs caused radial forces to be applied to the nozzle, making it bind in the receptacle. Additionally, the F-22 also didn’t consider stiff boom characteristics, causing the Raptor to have rapid forward movement of the aircraft relative to the KC-46.
The last investigation involved a KC-46 from the 22nd Air Refueling Wing at McConnell AFB, Kansas, and an F-15E from the 366th Fighter Wing at Mountain Home AFB, Idaho, on Aug. 21, 2024. During the flight, the nozzle became bound in the Strike Eagle’s receptacle, and during release, the boom rapidly flew upward, violently oscillating left and right, and struck the KC-46. The incident caused a critical failure of the boom’s shaft structure, with portions detaching in flight. Damages were estimated at $14.3 million.
The investigation found the mishap was caused by the boom operator’s control inputs, coupled with the aircraft’s excessive close rate and instability.
Air Mobility Command said another nozzle-binding incident occurred July 8, 2025, though that investigation still is ongoing.
Following the investigations, AMC has specified training for refueling involving fighter aircraft and increased the refueling envelope to 10 ft. from 6 ft., giving operators additional time to react.
The boom is being redesigned to address the stiff boom deficiency, with the fix expected to be fielded in 2026. The tanker’s remote vision system also is being redesigned on approximately the same timeline.
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