[Updated Thursday with details on third, aborted landing attempt] Two out of three ain’t bad, if you’re trying something no one’s ever done before.
After all the VIPs and reporters had been hustled off the USS George H.W. Bush, however, a third attempt had to be aborted when the experimental X-47B‘s electronic brain “self-detected a navigation computer anomaly,” a Navy spokesman emailed reporters this evening at 7:30. The drone diverted to a landing field ashore without further incident.
[Updated Thursday: In fact, not only did the drone detect the problem itself, it made its own decision to break off the landing, Navy officials told reporters in an after-action review the next day.
"It was on final approach," said Rear Adm. Mathias Winter, the one-star admiral who oversees all Navy drone programs. "[It was] about four miles aft of the ship, the [tail] hook was down, the [landing] gear was down, and as it’s supposed to do, it continues to check the health and status of all its subsystems.”
Specifically, the X-47B has three navigation computers that constantly cross-check each others’ results: “When you’re flying that close to personnel and other aircraft, you just have to be sure,” said the Navy’s X-47 program manager, Capt. Jaime Engdahl. But, he said, “about two minutes prior to landing,” one of the three computers came up with a result the other two disagreed with.
That discrepancy was enough for the drone to decide — on its own and without human intervention — that it should “wave off,” to use the Navy term for breaking off a landing attempt. So the X-47B flew past the carrier instead of touching down and reported the problem to its human controllers, who told it to execute the better-safe-than-sorry back-up plan and return to shore.