Boeing Expects to Resolve KC-46 Flight Management, Drain Tube Issues This Year

By Frank Wolfe | February 2, 2022
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A KC-46 Pegasus of the 97th Air Mobility Wing takes off July 20, 2021 during the Combat Raider exercise at Ellsworth Air Force Base, South Dakota. Combat Raider is an annual large force training exercise designed to train various aircrews in high-end, realistic scenarios supporting a full range of operations. (U.S. Air National Guard photo by Senior Airman Taylor Solberg)

This year, Boeing is redesigning a drain tube for its KC-46A Pegasus tanker for the U.S. Air Force and is working with General Electric to resolve a flight management system instability issue that can occur on the aerial refueler, the Government Accountability Office (GAO) said in a new report.

“In March 2021, the Air Force identified a critical deficiency with the flight management system— which provides flight guidance and navigation support—after error messages occurred on a trans-Pacific flight,” the report said. “Program officials said Boeing is working with General Electric Aviation—the subcontractor— to develop a software fix for the instability issue, and that they plan to release it to fielded aircraft by September 2022. In the meantime, according to program officials, Boeing released procedural guidance for KC-46 aircrews should the errors reoccur.”

In addition, Boeing is redesigning a drain tube to avoid cracks in the tube at freezing temperatures.

In March 2021, “the Air Force identified a critical deficiency with the air refueling drain tube, which drains excess fuel in the air refueling receptacle after refueling operations,” GAO said. “The program said the drain tube cracked while the aircraft was flying in freezing temperatures and the water in the receptacle froze and expanded in the receptacle, and that Boeing has determined the root cause. This issue followed two other instances in January and February 2020. Program officials said that Boeing is developing a new drain tube, and they expect to retrofit delivered aircraft beginning in 2022.”

As the Air Force works to resolve Category 1 deficiencies on its KC-46A tankers, the service has been preparing to move forward on the KC-Y, a commercial “bridge tanker” to fill the gap between the delivery of the 179th KC-46A tanker in 2029 and the future KC-Z tanker.

The most troublesome Category 1 deficiency for the KC-46 has been the lack of depth perception of the Remote Vision System (RVS). Boeing has moved forward on a new RVS 2.0 system. GAO recommended that the Air Force test the new system on a prototype aircraft before closing preliminary design review for the plane, but Boeing disagreed.

“In its comments, the Air Force states that testing a full prototype of the new RVS is not practical because the system is highly integrated,” GAO said. “The Air Force states that testing an integrated prototype would delay the program approximately 18 to 24 months and significantly delay fielding of the system to the warfighter. The Air Force states that prototypes of the cameras have flown, and that the display has been evaluated in the laboratory.”

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