KC-46A pilots cannot take off until OBIGGS counts to zero

A category 2 deficiency for the KC-46A aerial refueling tanker is prevent pilots from taking off in the tanker until the On-Board Inert Gas Generation System (OBIGGS) countdown timer reaches zero.

A rainbow over Boeing Field, Seattle, Washington, as seen from the flight deck of a KC-46A Pegasus, just prior to its delivery flight to Pease Air National Guard Base, New Hampshire, Feb. 5, 2021.
The jet, which was the twelfth and final of Pease’s new fleet of aerial refuelers, was piloted by a crew from the base. (Courtesy photo/Col. Nelson Perron)

OBIGGS will fill the fuel tanks with nitrogen to prevent the tanks from exploding if there is residual fuel inside.

Maj. Tim McBride, an instructor pilot with the 931st Air Refueling Wing, told Defense News that the system take on average 1.5 hours to be ready. But occasionally, the countdown timer will reset and that increased the waiting time.

To fix the issue, the service has decided to amend the flight manual so that the flight crew can now take off even if the OBIGGS is still counting down. This will be implemented next month.

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