The U.S. Air Force's KC-46 tanker program office should have dealt with problems with the aircraft's refueling boom years ago, during its development, according to a May 27 Defense Department Inspector General report.
Instead, the service is working with Boeing Co., the tanker's manufacturer, to redesign the boom -- at a cost of $100 million.
The KC-46 Pegasus has had many issues, including how the boom connects and disconnects when refueling aircraft. Pilots flying certain receiver aircraft, such as the A-10 Warthog and F-16 Fighting Falcon, have reported the need to use more power to move the boom forward to maintain refueling position.
The IG found the issue dates back to 2012, a year after Boeing won a fixed-price contract to produce the service's new tanker. According to the findings, the KC-46 Program Office did not verify that "critical technologies for the KC-46A tanker refueling boom were demonstrated in a relevant testing environment."
That year, Boeing proposed a system configuration that included a new technology beyond the scope of the original boom design, which was based on the KC-10 Extender.
The office should have rigorously tested the new tech, which uses a computer control system, before moving on to the Engineering and Manufacturing Development phase of the program, the IG said.
When further tests began in 2014, the flights were conducted in a limited capacity. Officials deemed those tests to be sufficient, but problems later became apparent when refueling certain aircraft, including the C-17 Globemaster III.
Boeing continued updates to the boom's hardware and software elements, and the KC-46 still operated under limited flight tests in 2016.
Those reduced test conditions included A-10 close-air support aircraft and F-16 fighters flying at only one airspeed and one altitude combination while connecting to the KC-46. Researchers did not test other configurations for these aircraft -- such as carrying different weapons loads, which changes their center of gravity. During testing done in October 2016, the Air Force recorded a "number of instances" in which the KC-46's boom scraped the surface of receiving aircraft, according to Defense News.
"We concluded that eliminating the most stressing aircraft test conditions or deferring these tests prevented KC-46 Program Office officials from determining the full impact of the refueling boom high axial load problem" at the Milestone C approval phase, the report states. Milestone C determines whether equipment can proceed into the production and deployment phase of a program.
Despite the problems, the service OK'd the boom design.
In 2018, when boom problems occurred again with the A-10, F-16 and C-17, the IG blamed the limited flight test data, which "did not fully demonstrate that the KC-46A tanker was capable of refueling light-slow, heavy, and light-fast receiver aircraft" in accordance with the test and evaluation program requirements, known as the Test and Evaluation Master Plan.
It forced the service to declare a Category I deficiency on the KC-46, defined as a critical flaw that impacts the development, schedule and, potentially, safety of the aircraft and the personnel on board.
"Had KC-46 Program Office officials effectively managed the development and testing of the refueling boom for the KC-46A tanker, the Air Force would not have had to spend an additional $100 million for the redesign of the refueling boom to achieve its required performance," the IG concluded.
There are also other issues with the KC-46. The chief problem is a glitch in its Remote Vision System, or RVS, software, which does not allow a clear visual of the boom connecting to another aircraft. The Air Force continues to work with Boeing to fix the troubled tanker, which was first delivered in January 2019 despite that problem.
Gen. Jacqueline Van Ovost, head of Air Mobility Command, said that while the KC-46 still isn't ready for an overseas deployment to a combat region, the tanker will start accepting mission tasks from U.S. Transportation Command on a case-by-case basis.
But because of the RVS issue, the tanker's expected readiness to deploy to the Middle East, Indo-Pacific and Europe has been pushed back to at least 2023.
Boeing has delivered more than 40 KC-46s to the Air Force. The service plans to buy 179 aircraft.