The Northrop Grumman X-47B landed twice aboard the USS George H.W. Bush aircraft carrier, but a malfunction with one of its three navigation computers prevented a third landing. The aircraft subsequently diverted to Wallops Field, Virginia, as programmed, for a safe recovery.
"There are three redundant navigation computers on the X-47," says Capt Jaime Engdahl, the US Navy's programme manager for unmanned systems. "We saw an issue on one of those computers and decided we had done enough for the day, flew the aircraft back and landed it."
The aircraft makes its approaches autonomously, without human interference. The computers onboard the aircraft noted the anomaly affecting one of the three precision GPS computers, and though capable of landing using only one, the aircraft is coded to abort landing under those circumstances. After the automatic abort, the human controller elected to divert the aircraft instead of continuing.
"They're working through the data right now," says Carl Johnson, Northrop Grumman's programme manager. "In terms of a malfunction it's probably a minor issue, that when we reset the computers everything will be up and running and we'll have a fully functional aircraft."
Two X-47Bs are flying. The aircraft used for the test has the tail number 502. An identical aircraft, tail number 501, will likely be used for the next aircraft carrier test series on 15 July. If all goes well in the second series, the X-47B's tests will be completed and the aircraft retired. A manned Learjet using X-47B's software will conduct autonomous air-to-air refueling trials in 2014.
The lessons learned from the X-47B demonstrations will be used to address the Unmanned Carrier-Launched Airborne Surveillance and Strike (UCLASS) programme, meant to essentially create an operational production UAV for aircraft carriers. Four companies - Northrop, Lockheed Martin, Boeing and General Atomics Aeronautical Systems - have been selected to perform design work.