A “single point of failure” led to a catastrophic crash on September 4, 2022, at Mutiny Bay, Whidbey Island, Washington, in the United States, resulting in the death of the 43-year-old pilot and nine passengers, the National Transportation Safety Board (NTSB) reports.
The de Havilland DHC-3 Otter floatplane took off from Friday Harbor Seaplane Base for Will Rogers Wiley Post Memorial Seaplane Base, but around 20 minutes into the journey the flight ended in disaster.
Witnesses reported, and surveillance video confirmed, the aircraft was in level flight before it climbed slightly and then abruptly pitched down, descending at an estimated rate of more than 9,500 feet per minute until it impacted the waters of Mutiny Bay, off Whidbey Island.
Several witnesses described the airplane as “spinning,” “rotating,” or “spiraling” during portions of the near-vertical descent and one witness reported hearing the engine/propeller and noted that he did not hear any “pitch change” in the sounds.
The West Isle Air operated Otter sunk 200 feet and there were no survivors.
In its final report, the NTSB said that examination of the aircraft revealed that the clamp nut that attaches the top eye end and bearing assembly of the horizontal stabilizer trim actuator to the actuator barrel had unscrewed from the barrel.
What’s more the NTSB found that the circular wire lock ring, which was designed to prevent the clamp nut from unscrewing, was not present.
With the actuator disconnected from a control linkage, it would have made it impossible for the pilot to control the plane’s pitch.
Evidence led the NTSB to conclude that the flight control failure happened before the crash, not as a result of it.
Such was the concern that on October 26, 2022, the NTSB issued an urgent recommendation to the Federal Aviation Administration (FAA) and Transport Canada to require all operators of DHC-3 airplanes to…