Accident Overview
On a local electronic news gathering flight, two aircraft collided while operating near Lake Union. One aircraft, identified by its registration as N5735A, was transitioning the area in a south-southwesterly direction. The other aircraft, N206AC, was northbound after departing from Boeing Field. Both pilots were able to land their aircraft on nearby helipads following the collision.
Pilot Reports
The pilot of N5735A reported that he was monitoring the common traffic advisory frequency (CTAF) for Lake Union (122.90) and had announced his position, altitude, and heading just before transitioning the area. He stated that he simultaneously saw the other aircraft and felt the impact. After the collision, he initiated a descent and landed on a nearby helipad.
The pilot of N206AC stated that he had just cleared Boeing's Delta airspace and switched to Seattle Radio (122.50) when he experienced a loud bang and vibration in the main rotor system. He did not see the other aircraft before or after the collision. He initiated a descent to a nearby helipad and was able to land without further incident.
Aftermath
Both aircraft landed on helipads without further incident. The pilots reported no injuries, and the source did not provide details about damage to the aircraft. No mechanical failures or malfunctions were reported that may have contributed to the accident.
Investigation Findings
A calculated convergence angle between the two aircraft indicated that there were no visual restrictions that would have prevented the pilot of either aircraft from seeing the other. The source did not specify a probable cause for the accident.