T Hawk down.

The operator of the Fukushima Daiichi nuclear power plant says it lost control of an unmanned helicopter during a flight near the No. 2 reactor building, forcing the controller to make an emergency landing on a roof there.

Tokyo Electric Power Company says the remote-controlled light helicopter took off from an observatory south of the Fukushima plant just past 6:30 AM on Friday. Its mission was to collect airborne radioactive substances around the No. 2 reactor building.

The utility says its engine failed about 30 minutes later, making it impossible for the aircraft to ascend.

The helicopter — 50 centimeters long and weighing 8 kilograms — was found lying on its side on the rooftop.