Publicly Released: May 27, 2021
The objective of this evaluation was to determine whether the Air Force adhered to DoD and Air Force systems engineering processes during the design and development of the KC-46A aerial refueling boom.
The KC-46A Pegasus tanker is an aircraft whose mission is aerial refueling of DoD and Allied aircraft. The refueling boom is the component of the aerial refueling system that transfers fuel from the tanker to the receiver aircraft.
In February 2011, the Air Force awarded a fixed-price-incentive contract for the KC-46A tanker to Boeing. Under this contract, Boeing is responsible for designing, developing, testing, and manufacturing 179 KC-46A tankers for delivery to the Air Force. The Air Force contracted with Boeing to deliver the KC-46A tankers in August 2017; however, deliveries did not begin until January 2019. As of October 2020, Boeing delivered 38 of the required 179 KC-46A tankers to the Air Force.
KC-46 Program Office officials did not effectively manage the development of the refueling boom for the KC-46A tanker. Specifically, KC-46 Program Office officials:
- did not ensure that critical technologies for the refueling boom were demonstrated in a relevant testing environment after Boeing officials presented a system design at the preliminary design review in 2012 that differed significantly from the initially proposed design; and
- did not verify full functionality of the KC-46A tanker refueling boom in accordance with the program’s Test and Evaluation Master Plan when they performed flight testing of the KC-46A tanker refueling boom with Air Force receiver aircraft.
These shortfalls with the KC-46A refueling boom occurred because:
- officials from the KC-46 Program Office did not revalidate changes to critical technologies or technology maturity at any point during the engineering and manufacturing development phase, since revalidations were not required by DoD policy; and
- officials from the KC-46 Program Office decided, and officials from the Office of the Deputy Assistant Secretary of Defense for Developmental Test and Evaluation accepted, in 2014 that reduced flight testing was sufficient to evaluate the performance of the KC-46A tanker in support of the Milestone C decision in 2016. Despite encountering flight test failures in January 2016 that required Boeing engineers to redesign the refueling boom, the KC-46 Program Office officials did not change their decision to perform reduced flight testing prior to the Milestone C decision. This reduced flight testing did not include the stressing conditions under which the refueling boom problem could potentially occur.
As a result, in 2018, when Boeing attempted to test full functionality of the KC-46A tanker refueling boom after Milestone C, flight test reports documented that refueling boom performance remained a problem during in-flight refueling of the A-10, C-17, and F-16 receiver aircraft. Specifically, the 38 KC-46A tankers that Boeing delivered could not refuel the A-10 or several variants of the C-130 receiver aircraft, and Air Force officials imposed operational limitations allowing the B-52, C-17, F-15, F-16, F-35A, HC/MC-130J, KC-10, KC-46A, and KC-135 receiver aircraft to aerially refuel only under limited flight conditions.
In August 2019 and March 2020, the Air Force issued contract modifications, valued at $100 million, for the redesign of the KC-46A tanker refueling boom. 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. Furthermore, retrofit of the refueling boom for the delivered KC-46A tankers is not estimated to begin until January 2024, and will result in additional undetermined costs, as well as approximately a 5-year delayed delivery of the first KC-46A tankers with fully mission-capable refueling booms. This delay limits the DoD’s use of the KC-46A tanker for its intended refueling missions.
We recommend that the Under Secretary of Defense for Research and Engineering and the Under Secretary of Defense for Acquisition and Sustainment revise DoD acquisition policy to require program managers of major defense acquisition programs to:
- Conduct knowledge-building technology readiness assessments throughout the acquisition life cycle, including at preliminary design review, critical design review, and Milestone C, at a minimum.
- Develop and execute technology maturation plans for critical technologies that have not been demonstrated in a relevant testing environment, as determined by a knowledge-building or statutory technology readiness assessment.
Additionally, we revised the following two recommendations:
- Use scientific test and analysis techniques to the maximum extent possible to develop the Test and Evaluation Master Plan.
- Use scientific test and analysis techniques to the maximum extent possible to justify the elimination, deferral, or modification of planned tests that were originally documented in the Test and Evaluation Master Plan.
Finally, we added two recommendations:
- Include the most critical or stressing test conditions in the Test and Evaluation Master Plan for any tests where the use of scientific test and analysis techniques is impractical or not applicable when developing the Test and Evaluation Master Plan.
- Include the most critical or stressing test conditions in revised test plans when proposing elimination, deferral, or modification of planned tests that were originally documented in the Test and Evaluation Master Plan.
Management Comments and Our Response
The Director of Developmental Test, Evaluation, and Assessments, responding for the Under Secretary of Defense for Research and Engineering, in coordination with the Under Secretary of Defense for Acquisition and Sustainment, agreed with two recommendations related to the use of knowledge-building technology readiness assessments and technology maturation plans. Additionally, the Director partially agreed with the two recommendations related to the use of scientific test and analysis techniques to develop the Test and Evaluation Master Plan and for proposing the elimination, modification, or deferral of planned tests documented in the Test and Evaluation Master Plan.
Although the Director agreed, his comments only partially addressed our recommendations. Therefore, the recommendations are unresolved.
We request that the Director provide additional comments on the final report to describe the specific actions that the USD(R&E), in coordination with the USD(A&S), will take to address the recommendations. Management comments and our response are discussed in detail in the Recommendations, Management Comments, and Our Response section of this report.
This report is the result of Proj. No. D2019-DEV0SR-0199.000.