Eurocopter AS 350 B3 N791AM accident near San Diego, California

Probable cause

The pilot’s failure to maintain altitude during a hover taxi due to distraction resulting from the unanticipated activation of strobing lights while using night vision googles.

NTSB analysis

The pilot of the helicopter reported that he had completed an operational mission, during which he was wearing Night Vision Goggles (NVGs), and returned to the airport. While hover taxiing to parking using the NVGs, an aircraft approaching the airport to land triggered the Traffic Collision Avoidance System (TCAS), causing the helicopter’s strobing “wig-wag” lights to activate and impact the pilot’s visibility. The pilot looked down to locate the light switch and removed his hand from the collective to deactivate the lights. The helicopter descended and contacted the ground before the pilot could stop the descent. The helicopter subsequently became airborne again and the pilot was able to regain control and continue hover taxiing to parking. Substantial damage to the tail boom was discovered after the flight. The pilot reported that there were no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation.

Text from the NTSB. Open the NTSB docket for WPR23LA200 for the full record.