What happened
A flight instructor and a student were conducting a training session in a Robinson helicopter at North County. After approximately 46 minutes of flight, the instructor decided to demonstrate a 180-degree autorotation. During this time, the pilot of a Piper airplane was engaged in glider towing operations.
The helicopter pilot announced on the common traffic advisory frequency (CTAF) that the aircraft was turning left downwind at 500 feet for the practice autorotation. The Piper pilot reported seeing the helicopter at the start of its downwind leg and subsequently announced his takeoff. Witnesses observed the helicopter on the downwind leg while the airplane began its takeoff roll.
A pilot of a towed glider noted that the helicopter was positioned slightly above and behind to his left, paralleling the flight path of the airplane. The airplane and helicopter collided during this maneuver. Following the impact, the airplane continued straight for a short distance before descending with a nose and left-wing low attitude into a marsh. The helicopter impacted the ground.
The investigation
Post-accident examinations of both aircraft determined that the main rotor of the helicopter made contact with the left main landing gear tire of the airplane and a section of the airplane's left wing leading edge.