What happened
On the day of the accident, two float-equipped de Havilland DHC-6 aircraft were moored at a dock for sightseeing flights. The aircraft with registration N235SA was moored at the dock with passengers boarded while the two pilots completed preflight duties; its engines were not running. Positioned approximately four feet behind it was another de Havilland DHC-6, registered as N353PM, which had completed pre-taxi checks and had its engines running.
During the operation, the pilot in command of N353PM signaled a dockhand to disconnect the shore power. After disconnecting the power, the dockhand released the mooring ropes without receiving any instruction to do so. Under idle power, N353PM surged forward and struck the tail of N235SA. The collision resulted in substantial damage to both aircraft.
Findings
At the time of the accident, company procedures required the dockhand to wait for a specific signal from the pilot before releasing the mooring ropes. The investigation determined that the dockhand released the lines prematurely. Following the incident, the operation moved to a longer dock to increase the distance between aircraft, and procedures were updated so that the first officer is now responsible for releasing mooring ropes only upon the pilot's direction.