Bell 407 N450AM accident near Union Center, South Dakota

Probable cause

The ambulance driver’s failure to see the helicopter’s rotating main rotor blades in dark night conditions, which resulted in the ambulance’s inadvertent collision with the helicopter. Contributing to the accident was the ambulance driver's failure to follow procedures when approaching the helicopter.

NTSB analysis

The helicopter pilot, flight nurse, and flight paramedic had arrived at a landing zone to pick up a patient at night. After landing, the pilot rolled the engine throttle to idle and briefed the flight crew that they were clear to depart the helicopter. About 20 seconds later, the ground ambulance drove toward the helicopter, and the main rotor blades impacted the top of the ambulance. The flight paramedic was thrown to the ground and sustained minor injuries. The main rotor blades, tailboom, and fuselage sustained substantial damage. The ground ambulance driver stated that he saw the crew open the doors and get out of the helicopter, so he moved the ambulance ahead to get closer to the helicopter. The driver stated that he did not realize "that the helicopter blades were still rotating." The operator confirmed that the ambulance driver had received training, which indicated that ground personnel are not to approach the helicopter until the blades had stopped rotation. In addition, the general operations manual stated that ground personnel will not come beneath the rotor disk until directed to do so by the pilot.

Text from the NTSB. Open the NTSB docket for CEN19LA092 for the full record.