Probable cause
The in-flight unthreading of the clamp nut from the horizontal stabilizer trim actuator barrel due to a missing lock ring, which resulted in the horizontal stabilizer moving to an extreme trailing-edge-down position rendering the airplane’s pitch uncontrollable.
NTSB analysis
HISTORY OF FLIGHTOn September 4, 2022, about 1509 Pacific daylight time, a float-equipped de Havilland DHC-3 (Otter), N725TH, was destroyed when it impacted the water in Mutiny Bay, near Freeland, Washington, and sank. The pilot and nine passengers were fatally injured. The airplane was owned by Northwest Seaplanes, Inc., and operated as a Title 14 Code of Federal Regulations (CFR) Part 135 scheduled passenger flight by West Isle Air dba Friday Harbor Seaplanes. The flight originated at Friday Harbor Seaplane Base (W33), Friday Harbor, Washington, with an intended destination of Will Rogers Wiley Post Memorial Seaplane Base (W36), Renton, Washington. Visual meteorological conditions prevailed at the time of the accident.
Text from the NTSB. Open the NTSB docket for DCA22MA193 for the full record.
Event
- Date
- Sep 4, 2022
- Type
- Accident
- Place
- Freeland, Washington
- Highest injury
- Fatal
- Fatal injuries
- 10
- Weather
- Visual (VMC)
- Light
- Day
Dehavilland DHC-3
- N-number
- N725TH
- Category
- Airplane
- Year built
- 1967
- Damage
- Destroyed
- Operating rule
- Part 135 (charter and commuter)
From the NTSB aviation accident database: N-registered aircraft, events since 2008, data through Oct 28, 2026. The file is published monthly, so the latest weeks are incomplete and recent records can change. The official source is the NTSB aviation investigation search. CheckAero is independent and not affiliated with the NTSB.