CEN13CA114 · Bell 407

The accident occurred as the air medical flight was departing a hospital heliport en route to pick up a patient. Another helicopter was parked off to the side of the helipad but within the fenced helipad area. Before boarding the departing helicopter, the pilot turned the main rotor blades on the parked helicopter to give him more room to maneuver on takeoff. During takeoff, the pilot was turning the helicopter into the wind and talking to an air traffic controller when he backed the helicopter into the main rotor blades of the parked helicopter. The pilot rolled the throttle to idle and conducted a hover autorotation back onto the helipad. The pilot later reported that he knew the parked helicopter was there but had forgotten about it. The accident helicopter sustained substantial damage to both tail rotor blades and one of the main rotor blades. The pilot was unable to hear the medical crew's warnings over the intercom because the microphone was keyed for the conversation with the air traffic controller. The operator’s general operations manual provides minimum clearance guidelines that state, in part, that minimum clearances for all helicopters will be at least 1/3 of the rotor diameter between the outboard tip of the rotor disc and any obstruction and at a distance great enough not to create a hazard to persons or property on the ground in non-secured areas. These guidelines were most likely met before the accident.

Verbatim NTSB analysis and probable cause from the NTSB dataset