The experimental U.S. Navy drone that became the first unmanned jet to land aboard a moving aircraft carrier was told to abort the third and final attempt after one of its navigational computers failed, officials said.
The bat-winged aircraft, known as the X-47B and made by Northrop Grumman Corp., completed two touchdowns and takeoffs yesterday aboard the USS George H.W. Bush about 70 miles off the coast of Virginia Beach, Va., in what officials heralded as the future of naval aviation.
On the third approach, the drone reported that one of its three navigational computers failed, so the human operator instructed the craft to fly to a runway at Wallops Island, Va., according to Rear Adm. Mat Winter, the service's program executive officer for unmanned aviation and strike weapons.
"On every test, we have some type of anomalous behavior," Winter said today during a conference call with reporters. "X-47B did everything it was designed to do."
The incident occurred about two minutes prior to the last planned landing as the aircraft approached the ship, according to Capt. Jaime Engdahl, who manages the Navy's Unmanned Combat Air System Demonstrator, or UCAS-D, program.
"We saw an issue with one of the precision navigation computers and decided that we had done enough for the day and then flew the aircraft back," Engdahl said during the call.
"Landing aboard an aircraft carrier is extremely demanding," he added. "The accuracy, the integrity, the reliability that you need is critical to the safety of the aircraft and the fact that we're landing on a ship in close proximity to flight deck personnel and other aircraft."
Officials are reviewing the data to determine what happened to the navigational computer, according to Carl Johnson, a vice president at Falls Church, Va.-based Northrop who manages the program for the company.
"It's probably a minor issue that when we reset the computers, everything will be up and running and you'll have a fully functioning aircraft," he said during the call.
The prototype that flew the mission, which has the call sign "Salty Dog 502," is one of two Northrop built for the Navy. The aircraft will return to Naval Air Station Patuxent River, Md., after final testing aboard the ship is completed on Monday, Winter said. They will eventually be retired to a museum.
The development program has cost about $1.4 billion over eight years, according to the Navy.
The effort was designed to demonstrate the technology's potential and pave the way for a larger program, called Unmanned Carrier Launched Airborne Surveillance and Strike, or UCLASS, to build an armed, carrier-based drone fleet.
The Navy wants to add operational drones to air wings in 2019 to extend the range of carrier groups. Unmanned aircraft can stay aloft for more than a day -- far longer than manned planes. The systems will be initially used for surveillance and refueling missions, and eventually for strike operations, officials said.
The Navy plans to issue a draft request for proposals for the first phase of the UCLASS program in August, followed by a formal request to start the competition next year, Winter said. The service would pick a single winner by the end of 2014, he said.
Northrop Grumman is expected to square off against other defense giants for the work, including Lockheed Martin Corp., Boeing Co. and General Atomics Aeronautical Systems Inc. Lockheed Martin is pitching the Sea Ghost, Boeing the Phantom Ray, and General Atomics the Sea Avenger.