The KC-46 Pegasus tanker is still suffering from low mission capable and availability rates stemming from parts shortages, the Pentagon’s test director reported recently. The program continues to grapple with significant system deficiencies as well.
“The KC-46A is not meeting many of its suitability metrics,” according to the 2024 annual report from the office of the Director of Operational Test and Evaluation. The tanker’s operational availability requirement is 80 percent and the mission capable requirement is 90 percent, but the actuals “decreased throughout 2024,” the report noted.
The report did not disclose what those rates were, but according to the most recent public data from the Air Force, the KC-46 had a mission capable rate of 65 percent in 2023.
When accounting for partially mission capable aircraft unable to perform their primary air refueling mission—due to a broken boom, for example—“the effective mission capable rate falls an additional 24 percent on average,” the report noted.
The mission capable/availability figures have been distilled from “over 90,000 flight hours of maintenance data” analyzed by the Joint Reliability and Maintainability Evaluation team. The Air Force Operational Test and Evaluation Center “has collected 15 times its originally required operational suitability flight test data, and no longer tracks detailed suitability data,” but the program office does.
The wealth of data is due in part to the fact that the KC-46 has been in initial operational test and evaluation since May 2019, even though AFOTEC has collected “all the achievable aerial refueling and secondary mission data on the current configuration” of the aircraft, the report noted.
The tanker can’t progress to the next stage of testing, however, until it receives updates to the refueling boom and the Remote Vision System, which are undergoing redesigns. AFOTEC has completed operational testing of the Wing Aerial Refueling Pod system and cooperative cyber testing of avionics systems.
There are some “potential concerns” with the WARPs under icing conditions, the test unit said, but the Air Force told DOT&E that it can use the existing system if needed and that it’s “pursuing a long-term solution.” There is also a weight and balance issue when the WARPs are installed, specifically when refueling both boom-type and drogue-type receiver aircraft. This is “expected to be resolved in a future weight and balance tool software upgrade.”
The Air Force “continues to work with Boeing to develop critical upgrades to the refueling boom and RVS, to support starting integrated testing in late FY25,” the report noted.
The problems with the boom and RVS are well known and have persisted for years now as Category 1 deficiencies—those that could cause death or serious injury to personnel or severe damage to the weapon system.
The Air Force has worked around some of these problems, and the KC-46 is now able to refuel 26 of 27 possible aircraft, but with some restrictions that “limit availability in certain environmental conditions and aircraft configurations,” the report noted. The final aircraft to go is not specifically identified in the DOT&E report but is the A-10 attack aircraft. Testing will resume after boom fixes are completed.
Other Category 1 problems include “the fuel manifold system, cracks and leaks in the refueling receptacle drain line, and cracks in the auxiliary power unit drain mast.” These have not been resolved, but redesigns are in progress.
Software updates to the Radio Frequency Self Defense System are needed to improve the tanker’s survivability, the report added, and flight testing of the RFSDS Version 6.0 is to get underway this quarter. These updates should “improve the clarity of information presented to aircrew to support threat avoidance capabilities,” the report states. More testing will be needed to see if those updates are sufficient to protect the KC-46 in a contested environment.
More broadly, the KC-46 “continues to suffer from prolonged maintenance repair times due to supply issues with parts,” the report added.
One of the issues driving “significant parts demand, additional maintenance and … damage to the aircraft” is a systemic failure of bleed air ducts, the report said. The problem, first identified in late 2023, was initially designated a Category 2 deficiency, but given “the number of aircraft affected [and] the number of repeat failures,” the program office upgraded the deficiency to a Category 1.
“This upgrade is appropriate due to no known acceptable workarounds in terms of supply support, repair support, and the significant additional burden on maintenance,” the report said. Boeing and the Air Force are “currently modeling and flight testing temporary procedures to alleviate the issue as they validate the temporary workarounds and future design modifications.” So far, “this deficiency is not considered a safety of flight issue.”
The test director did note some successes for the program. The KC-46 completed a Maximum Endurance Operation in June 2024, in which two KC-46 aircrews from the 22nd Air Refueling Wing completed a 45-hour “nonstop circumnavigation flight” beginning and ending at McConnell Air Force Base, Kan.
Boeing is on contract for 158 of 179 planned KC-46s. As of late 2024, some 89 aircraft had been delivered. The last contract, for the 15 aircraft in Lot 11, was awarded in November 2024. Its value was $2.4 billion, or about $159 million per airplane. Boeing is building the KC-46 under a fixed-price contract, and so far has absorbed more than $7.5 billion in losses on the program. The company was not immediately able to provide comment on the DOT&E report.