USAF probes tie three KC-46A boom mishaps to nozzle binding

The US Air Force Air Mobility Command has released three Accident Investigation Board reports that trace recent KC-46A Pegasus mishaps to nozzle-binding events during fighter refueling, with investigators pointing to a mix of boom-operator inputs, receiver handling inside tight envelopes, and the tanker’s control-law behavior at the edge of normal operations.  

The cases involve aircraft from the 305th Air Mobility Wing at Joint Base McGuire-Dix-Lakehurst on October 15, 2022, and November 7, 2022, and from the 22nd Air Refueling Wing at McConnell AFB on August 21, 2024. 

“The KC-46 tanker fleet will sustain our air refueling mission capabilities for decades to come,” said Lieutenant General Rebecca Sonkiss, AMC Deputy Commander. “Challenges with adding a new aircraft to the fleet are not uncommon but we do not take these incidents lightly. We have used the lessons learned to refine our KC-46 operations, including focused training and guidance while partnering with the contractor to implement long-term solutions.” 

AMC said early indicators from these events prompted specified training for fighter refuelings and a widening of the working refueling envelope from six feet to 10 feet to give boom operators more reaction time and clearer visual cues of the receiver’s motion. 

The North Atlantic, October 15, 2022: F-15E breakaway, tail strike 

During a routine refueling with an F-15E Strike Eagle from the 335th Fighter Squadron, 4th Fighter Wing out of Seymour Johnson AFB, a nozzle-binding event during a breakaway caused the KC-46A’s boom to surge upward and strike the tanker’s tail cone. 

The tanker was operated by the 2nd Air Refueling Squadron, 305th Air Mobility Wing. The board attributed the cause to a limitation in the boom control system that allowed inadvertent radial loading on the nozzle, creating the binding. Once the boom flew up, an automated-control limitation left it effectively uncontrollable, preventing protections that might have slowed the strike.  

The report also notes coordination issues as airspeed approached limits and highlights the KC-46A’s known “stiff-boom” handling that requires receivers to use more fore-aft thrust while in contact. 

Off Florida, November 7, 2022: F-22 breakaway, nozzle damage 

In a joint-force training exercise out of Tyndall AFB, a KC-46A operated by the 2nd Air Refueling Squadron, 305th AMW departed NAS Cecil Field, Florida, to refuel an F-22A Raptor from the 94th Fighter Squadron, Joint Base Langley-Eustis.  

There again, a nozzle-binding event during a breakaway with the Raptor damaged the KC-46A’s nozzle beyond repair. The investigation concluded the boom operator applied manual inputs that induced radial force, binding the nozzle in the receiver’s receptacle. Contributing factors included the receiver pilot not accounting for the KC-46A’s stiff-boom characteristics and the boom operator’s inability to verify the nozzle was clear before making inputs.  

Travis AFB sortie, August 21, 2024: boom strike and structural fracture 

During an Operation Noble Eagle mission, a KC-46A from the 931st Air Refueling Wing, 22nd Air Refueling Wing, based at McConnell AFB, launched from Travis AFB to refuel an F-15E from the 366th Fighter Wing. 

On the fourth refueling attempt, nozzle binding caused the boom to whip upward into the underside of the tanker, followed by violent lateral oscillations that fractured the boom shaft and sent pieces departing the aircraft mid-flight. The crew declared an emergency and returned safely to Travis. 

The investigation found the cause to be the boom operator’s control inputs that produced an excessive fly-up rate, compounded by the receiver’s excessive closure rate and instability. The board also cited an attempted contact outside the F-15E’s standard envelope, delayed breakaway by the receiver pilot, and gaps in the operator’s understanding of boom flight-control logic. No injuries were reported. 

Why nozzle binding keeps causing trouble for the KC-46A

Across all three investigations, “nozzle binding” is the trigger. Binding occurs when the boom nozzle becomes mechanically stuck in the receiver area without a full lock. If a separation happens under load, stored forces can catapult the boom into the tanker’s tail before protections can damp the motion.  

The reports underline how operator inputs, receiver stability inside published envelopes, and the KC-46A’s fly-by-wire control-law behavior intersect during these rare but high-consequence moments. Two boards explicitly reference knowledge gaps about boom flight-control logic once the system departs the normal regime, while the October 2022 report details how a control-law limitation left the boom uncontrollable during its upward motion. 

AMC says it has already focused training on fighter refuelings and widened the working envelope to increase margin, and it is coordinating with the contractor on longer-term solutions and training-device fidelity so crews can rehearse binding scenarios more realistically. 

The command also noted another nozzle-binding incident on July 8, 2025, remains under investigation; any additional mitigations will be determined once that inquiry is complete. 

No injuries, but real costs 

None of the incidents caused injuries or damage to civilian property. Material damage was significant, however. The boards assessed $8,307,257.93 for the October 15, 2022 F-15E event, $103,295.12 for the November 7, 2022 F-22 event, and $14,381,303.00 for the August 21, 2024 F-15E event, a combined total of $22,791,856.05. 

The KC-46 boom is currently being redesigned to address the “stiff boom” deficiency that has hindered reliable refueling of thrust-limited receivers such as the A-10, with fielding expected in 2026. These incidents also come as Boeing and the US Air Force roll out the Remote Vision System 2.0, a redesigned camera and sensor suite for boom operations. Deliveries began in April 2025, with full fleet integration projected by the end of fiscal year 2027. The original RVS drew criticism for depth-perception and image-quality issues in challenging lighting. 

Despite persistent delays and capability shortcomings, the USAF approved the KC-46A Production Extension Program in July 2025, ordering up to 75 additional Pegasus aircraft to accelerate fleet recapitalization and avoid a second tanker competition.  

The Pegasus was designed to eventually replace the KC-135 Stratotanker, a workhorse of the air mobility fleet since the late 1950s. But because of delays and capability gaps in the KC-46 program, the USAF now expects to retain part of its KC-135 fleet well into the 2050s. The venerable Stratotanker has undergone multiple modernization efforts, including avionics upgrades to extend its operational life. The post USAF probes tie three KC-46A boom mishaps to nozzle binding appeared first on AeroTime.

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