The Air Force and prime contractor Boeing [BA] on Monday got over one of their final hurdles before a critical program decision when the KC-46 aerial refueling tanker successfully refueled a C-17.

An initial refueling attempt with a F-16 earlier this year was successful, but higher than expected axial loads on the boom were detected, according to a service statement. These loads were again present during the initial attempt with the C-17 in February and necessitated installation of hydraulic pressure relief valves in the boom.

A KC-46 refuels a C-17 on July 11. Photo: Air Force.
A KC-46 refuels a C-17 on July 11. Photo: Air Force.

This week’s successful tests show the boom axial loads hardware fix, designed by Boeing engineers, is performing as expected to alleviate the loads. The KC-46 also refueled a F-16 on July 8.

The final Milestone C flight test, slated for this month, is to transfer fuel through the fixed boom to an A-10. Once this successfully takes place, the Air Force will ask Pentagon acquisition czar Frank Kendall to award low-rate initial production (LRIP) lots one and two, totaling 19 KC-46 aircraft.