ERA12FA527 · Bell 407

The pilot was transporting passengers across a lake and home from a race track at night. A witness who was boating on the lake across from the helicopter landing area watched the helicopter approach and land. He stated that the landing light was on during the landing. He watched the passengers exit the helicopter and then the helicopter lift off and turn toward the lake, descend down an embankment, and turn over the lake. The witness stated that the landing light was not on during the departure. The helicopter traveled about 150 yards when the bottom skids began to make the water spray. The helicopter then nosed over and impacted the water. The witness then directed his boat toward the impact area where he found the tail boom separated from the fuselage and the cockpit area submerged.

Examination of the fuselage, including the top Plexiglas window and frame, revealed evidence of main rotor contact. The helicopter's engine was torn from the fuselage and could not be located due to poor visibility in the water and its irregular bottom features. The engine control unit (ECU) was retrieved, and all of the data revealed that no engine operating exceedances occurred before impact, and no accumulated engine faults were recorded during the previous engine run. The ECU data and physical evidence are consistent with power being supplied to the main rotor at the moment of impact.

Security camera video footage revealed that the pilot had successfully conducted this low-level, rapid acceleration takeoff profile several times during the day when visual spatial references were plentiful. The available data and evidence, as well as the previous flights, are consistent with controlled flight into water while conducting a rapidly accelerating, low-altitude flight after takeoff over an unlit body of water in dark night conditions. The pilot's decision to attempt a such a takeoff at night without the aid of ambient light or the use of helicopter lights denied him the visual spatial references needed to assure safe terrain and obstacle avoidance. Additionally, the conditions during the flight were conducive to a type of pilot spatial disorientation known as "somatogravic illusion," in which aircraft acceleration may be misinterpreted by the pilot as an increasing nose-up pitch attitude and result in inappropriate nose-down control inputs.

Verbatim NTSB analysis and probable cause from the NTSB dataset