Mechanical issue may have caused fatal seaplane crash

SEATTLE (AP) — A mechanical problem may have caused the seaplane crash that killed 10 people off an island in Washington state last month, US investigators said Monday.

The National Transportation Safety Board, the agency investigating the Sept. 4 crash off Whidbey Island, said it appeared a critical part that moved the plane’s horizontal tail stabilizer s was detached, The Seattle Times reported.

That part may have failed because a clamp nut unscrewed and spun due to a missing or improperly installed lock ring, investigators found.

Failure of the component, called an actuator, during flight “would cause the horizontal stabilizer to float, allowing it to spin uncontrollably … around its hinge, resulting in possible loss of control of the aircraft,” the NTSB said.

The plane, a de Havilland Canada DHC-3 Otter turboprop operated by Renton-based Friday Harbor Seaplanes, crashed into Puget Sound, killing the pilot and all nine passengers. It was about a half-hour flight to the Seattle suburb of Renton from Friday Harbor, a popular tourist destination in the San Juan Islands.

Investigators said that when the wreckage was recovered, the upper part of the actuator was still attached to the horizontal stabilizer while the lower part was attached to its bracket in the fuselage.

The most recent overhaul of the aircraft’s horizontal stabilizer actuator was completed on April 21. complete insertion of the locking ring.

“At this time, the NTSB does not know if the lock ring was installed before the aircraft touched the water or why the lock ring was not present when the aircraft was examined. ‘plane,’ the agency said.

The NTSB and the Transportation Safety Board of Canada have asked the manufacturer to write instructions for all operators of DHC-3 aircraft to inspect the actuator to ensure that the locking ring is properly installed to prevent unscrewing the clamping nut.

Witnesses who saw the plane’s nose dive into Mutiny Bay helped officials identify the crash site. Still, it took over a week and three types of sonar to locate what was left of the plane due to its depth and the current of the channel where the plane struck the water.

Crews using remote-controlled vessels and cranes recovered the majority of the aircraft wreckage from the sea floor more than 150 feet (46 meters) below the surface in late September.

Among the victims were a civil rights activist, a business owner, a lawyer, an engineer and the founder of a wine estate and his family.

Six bodies were recovered. These include the body of Gabby Hanna, 29, who was found by witnesses on the day of the accident, and five others found during recovery efforts.

Elisha A. Tilghman