Two de Havilland Canada DHC-6 Twin Otter aircraft were being prepared for flight while parked next to each other. Both aircraft were scheduled to operate a positioning flight, under Visual Flight Rules, from Sebastian Municipal Airport (Florida, USA) to George Town-Exuma International Airport (Great Exuma in The Bahamas).
After completing the required flight preparation checklists both pilots started the engines of their respective aircraft. The pilot of the aircraft on the righthand side of the pair of Twin Otters slightly advanced the throttles to bring the generators online. The pilot noticed the aircraft started to move to the left, the nose wheel tiller had been left in a left input position after the last flight. When the pilot applied the brakes to stop the aircraft, there was no response and the aircraft continued to move to the left. After completing a near 180-degree turn before colliding with the adjacent aircraft. Both aircraft were shut down, there were no injuries to the crews of both aircraft. Damage to both aircraft was extensive, with damage to the right-hand wing and engine/propellors to both aircraft.
The aircraft with the unresponsive brakes had extensive damage to the fuselage above the cockpit while the aircraft which was hit had its propellor sheered off.
After completing the shutdown checklist the pilot of the aircraft with the unresponsive brakes noticed that the circuit breaker for the hydraulic pump was pulled. There was no record of maintenance being carried out on the aircraft before the accident which was related to the hydraulic system. During the investigation by the National Transportation Safety Board (NTSB), it remained unclear why the circuit breaker was pulled. The pilot of the accident aircraft stated that she,"...should have seen the pulled circuit breaker on the prestart flow."
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot's failure to conduct all of the required items on the Before Starting Engines checklist, which resulted in her failure to detect an open hydraulic circuit breaker and led to insufficient hydraulic pressure to operate the airplane's brakes, her subsequent loss of airplane control, and ground collision with an airplane.
Both aircraft were repaired and returned to service.
The National Transportation Safety Board Aviation Accident Final Report, which served as the source for this blog, can be accessed by clicking on the .pdf file below;
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