The US Navy has placed operating restrictions on Northrop Grumman MQ-8B Fire Scout after losing control of the aircraft on 2 August over restricted airspace near Washington, DC.
The unmanned helicopter breached National Capitol Region airspace after traveling 32km (20nm) in the wrong direction from NAB Patuxent River, Maryland, the Navy says.
Ground operators at Patuxent River lost contact about 75min after takeoff, the Navy says. The unmanned aerial vehicle (UAV) is programmed to return to base in such situations.
But the aircraft instead veered northwest, away from the base.
After shifting to another ground control station, the Fire Scout operator restored control of the aircraft.
"During this routine test flight, we found a software anomaly that allowed the aircraft not to follow its preprogrammed flight procedures," the Navy says. "We have identified the issue and have aircraft operating restrictions that will prevent this from happening again." The Navy also developed a software modification to correct the anomaly.
The Navy notes the MQ-8B fleet has compiled more than 1,000h in flight since December 2006.
"We are in the final stages of the investigation and plan on briefing leadership next week," the Navy says. "We anticipate resuming flight operations in early September."