The National Transportation Safety Board determined that the probable cause of the August 9, 2010, airplane crash into mountainous terrain near Aleknagik, Alaska, was the pilot's temporary unresponsiveness for reasons that could not be established from the available information. Contributing to the investigation's inability to determine exactly what occurred in the final minutes of the flight was the lack of a cockpit recorder system with the ability to capture audio, images, and parametric data.
"One of the greatest lessons from this tragedy is the powerful reinforcement of the need for onboard crash resistant recorder systems," said NTSB Chairman Deborah A.P. Hersman. "With onboard recorders, we can learn so much more from crashes like this one to prevent future tragedies and loss of life."
On August 9, 2010, at about 2:27 p.m., a single-engine de Havilland turbine Otter floatplane carrying a pilot and eight passengers departed a private lodge on the shore of Lake Nerka en route to a remote fishing camp approximately 52 miles southeast on the Nushagak River. The pilot was highly experienced and familiar with the route. However, during the flight, the airplane turned toward the east- northeast, away from the intended destination and crashed into mountainous terrain at about 2:42 p.m.
The pilot's medical history included an intracerebral hemorrhage in March 2006. His most recent first-class medical certificate was issued on December 1, 2009.
"This tragedy also highlights inadequate FAA guidance related to the medical certification of pilots who have had a cerebrovascular event," Chairman Hersman added.
As for the accident airplane, it was equipped with a variety of avionics designed to assist the pilot with navigation, situational awareness, and terrain avoidance. However, the airplane was not equipped with a cockpit voice recorder, flight data recorder, or other crash resistant flight recorder. Minutes prior to the crash, the last position report showed the plane on course. "What we do not know, and can never know," Chairman Hersman said, "is what happened in the last three minutes of that fatal flight."
The NTSB's full report will be available on the website in several weeks.