Mcdonnell Douglas Helicopter 600N N737TV accident near Delta Junction, Alaska

Probable cause

The pilot’s failure to clear the left landing gear skid, which resulted in the entanglement of the left landing gear skid with a log, and his subsequent application of collective pitch, which resulted in a dynamic rollover.

NTSB analysis

The pilot was transporting personnel from a remote elevated helipad constructed of logs. Witnesses stated that the helicopter had just touched down, and the pilot turned his head to give the signal to board when the helicopter suddenly pitched up and back, striking trees at the edge of the helipad. The helicopter rolled down the hill. A postaccident examination of the helipad revealed that one of the logs that made up the rear portion of the helipad decking had been pulled from the structure and damaged.

Based on the lack of mechanical anomalies with the helicopter and the damage to the helipad decking, it is likely the pilot landed too far forward on the helipad, which allowed the tail of the left skid to fall into the open area between the logs and become entangled. It is likely that the pilot sensed the imbalance and applied collective pitch, which resulted in a dynamic rollover.

Text from the NTSB. Open the NTSB docket for ANC12FA084 for the full record.