A Boeing KC-46A refuels a U.S. Air Force F-15 midair. (Photo: Boeing)
The U.S. Air Force expects to field a fix for the stiff aerial refueling boom (ARB) on the Boeing KC-46A Pegasus tanker late in fiscal 2027.
“The stiff boom deficiency is being resolved via the boom telescopic actuator redesign (BTAR) effort currently expected to field in late fiscal year 2027,” Air Force Life Cycle Management Center (AFLCMC) at Wright-Patterson AFB, Ohio said in an email response to questions on August 29.
The BTAR is expected to help avoid accidents that have resulted from “nozzle binding” on F-15E and F-22 Raptor fighters.
While the Air Force has cited the stiff ARB as an issue for the slower A-10 close air support aircraft, the stiffness has also been a problem for pilots of faster fighters, such as the Boeing F-15E Strike Eagle and Lockheed Martin F-22, and KC-46A boom operators have had problems with remote operation of the boom.
Such conclusions come from three Accident Investigation Board (AIB) reports Air Mobility Command (AMC) at Scott AFB, Ill., released on Aug. 25 regarding KC-46 accidents on Oct. 15, 2022; Nov. 7, 2022; and Aug. 21 last year.
The first involved a KC-46A from the 305th Air Mobility Wing at Joint Base McGuire-Dix-Lakehurst, N.J., and a “nozzle binding event” during which the plane’s ARB struck the aircraft’s tail section and caused more than $8.3 million in damage during a refueling attempt near Newfoundland of an F-15E Strike Eagle with the 335th Fighter Squadron at Seymour Johnson AFB, N.C.
A KC-46A from the 305th Mobility Wing had a similar “nozzle binding” with a 1st Fighter Wing F-22 Raptor fighter during a refueling off the coast of Florida on Nov. 7, 2022–a binding that caused the loss of the more than $103,000 nozzle.
In the third accident on Aug. 21 last year, a KC-46A with the 22nd Air Refueling Wing at McConnell AFB, Kan., had a “nozzle binding” over Switzerland while trying to refuel an F-15E from the 366th Fighter Wing at Mountain Home AFB, Idaho, and AIB assessed the resulting damage to be $14.4 million.
AIB said that “there is minimal discussion, if any, of the boom logic functions in the Flight Crew Operating Manual, the KC-46 Boom academics, or the [Air Force Tactics, Techniques, and Procedures publication] 3-3.b KC-46.”
“The only reference to fault detection out-of-range limit rates, ‘return to home’ function, and boom envelope soft limits were found in manufacturer proprietary and independent technical evaluation data specifically analyzed as a result of this mishap,” according to the AIB report. “There is currently a deficiency in the depth of boom system logic and boom flight control systems knowledge in KC-46 baseline manuals and academics. Additionally, many initial cadre flight instructors for the KC-46 were prior boom operators on the KC-135, which did not have any automated boom flight control systems. The tactics, techniques, and procedures for alleviating nozzle binding and ‘flying the boom’ in the KC-135 are contraindicated for the KC-46 automated systems and may have contributed to outdated techniques being taught during training.”
AMC first identified the KC-46A stiff boom as a Category I deficiency in a Sept. 10, 2018 report entitled Boom Telescope Too Stiff While In Contact With Receiver. In May, Air Force Chief of Staff Gen. Dave Allvin told the House Appropriations Committee’s defense panel that the KC-46A still has five unresolved Category 1 deficiencies–the stiff boom, two Category I deficiencies on the Remote Vision System, one on the mast drain, and one on the environmental control system.
“‘Nozzle binding’ is not uncommon during boom refueling and is a known issue for the KC-46 that when compounded with other factors can result in incidents like those associated with the AIBs,” AFLCMC said in the email answers on August 29. “‘Nozzle binding’ is generally not identified or recorded unless it results in such incidents.”
A version of this story originally appeared in affiliate publication Defense Daily.