The pilot's inadvertent activation of the collective flight stop/emergency fuel augmentation switch, which resulted in engine and main rotor overspeeds, thereby precipitating failures of the tail rotor drive shaft coupling and power turbine blades. A factor associated with the accident was the manufacturer's inadequate design of the flight stop switch, which has insufficient safeguards to preclude inadvertent activation.

THE CAPTAIN OF THE OTHER AIRCRAFT MISJUDGED CLEARANCE BETWEEN HIS AIRCRAFT AND THE STANDING COMMUTER AIRPLANE. A FACTOR WAS THE FAILURE BY THE SECOND PILOT OF THE OTHER AIRPLANE TO IDENTIFY A HAZARDOUS CONDITION.