Investigators pinpoint single point of failureWASHINGTON (Oct. 5, 2023) — The failure of a single component of a critical flight control caused the unrecoverable, near-vertical descent and subsequent water impact of a passenger airplane last year that claimed 10 lives, the National Transportation Safety Board said Thursday. The affected section of the flight control system was the subject of an urgent NTSB recommendation issued seven weeks after the accident.
On Sept. 4, 2022, a float-equipped de Havilland DHC-3 airplane carrying the pilot and nine passengers on a scheduled passenger flight between two seaplane bases crashed into Mutiny Bay, near Freeland, Washington. The airplane sank in about 200 feet of water; there were no survivors. The flight was operated by West Isle Air doing business as Friday Harbor Seaplanes.
Witnesses reported, and surveillance video confirmed, the airplane 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 water.
Working closely with the NTSB, the Navy Supervisor of Salvage and Diving recovered about 85 percent of the aircraft from the ocean floor, completing the mission 26 days after the crash.
Just days after NTSB investigators began examining the wreckage, they found the actuator that controls the pitch of the airplane had become disconnected from a control linkage, which would have made it impossible for the pilot to control the airplane’s pitch. Evidence led the NTSB to conclude that the flight control failure happened before the crash, not as a result of it.
On Oct. 26, 2022, the NTSB issued an
urgent recommendation to the Federal Aviation Administration and Transport Canada to require all operators of DHC-3 airplanes to conduct an immediate inspection of the affected section of the flight control system.
When the accident airplane’s design was certificated by the Federal Aviation Administration in 1952, there was no requirement for a secondary locking device to secure flight control linkages. In 1996, regulations were amended to require newly designed aircraft to have a secondary locking device “if the loss [of the first device] would preclude the continued safe flight and landing.” Since there was no requirement for retrofitting existing airplanes with a similar safety feature, the accident airplane had only a single locking device.
“The Mutiny Bay accident is an incredibly painful reminder that a single point of failure can lead to catastrophe in our skies,” said NTSB Chair Jennifer Homendy. “To adequately protect safety, we must build in the necessary redundancies across the entire aviation system.”
As a result of the investigation, the NTSB recommended the FAA and Transport Canada require operators of DHC-3 airplanes to install a secondary retention feature to prevent a single point of failure in the flight control system. Additional recommendations were made to both agencies as well as to the current type certificate holder, Viking Air.
“We’re calling on the Federal Aviation Administration and their Canadian counterparts to eliminate the safety vulnerability identified by NTSB investigators, so this kind of tragedy never happens again,” Homendy said.
The
59-page final accident report is available on NTSB.gov.
Links to the accident docket (opened on Sept. 1, 2023), investigative updates, related news releases, photos and other resources are available at
DCA22MA193
To report an incident/accident or if you are a public safety agency, please call 1-844-373-9922 or 202-314-6290 to speak to a Watch Officer at the NTSB Response Operations Center (ROC) in Washington, DC (24/7).
