2022 Mutiny Bay DHC-3 crash
West Isle Air de Havilland DHC-3 · Loss of pitch control due to Mechanical failure caused by maintenance error
From Friday Harbor Seaplane Base (W33) to Renton Municipal Airport (W36)
Event
- NTSB case
- DCA22MA193
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- Event fatalities
- 10 · all aircraft and ground
- Ground fatalities
- 0
- Occupants
- Unknown
- Survivors
- 0
- InjuriesFatal: death within 30 days. Serious: over 48 hours in hospital within a week, most broken bones, severe bleeding, nerve or organ damage, or serious burns. Minor: anything less. Glossary
- 0 serious · 0 minor (NTSB)
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- Charter & commuter
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
de Havilland DHC-3
- Aircraft type
- de Havilland DHC-3
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N725TH
- Operator
- West Isle Air
- Onboard fatalities
- Unknown
- Route
- From Friday Harbor Seaplane Base (W33), Friday Harbor, WATo Renton Municipal Airport (W36), Renton, WA
- Aircraft age
- About 55 years (built 1967)
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 135: Air Taxi & Commuter
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- En route
- Defining eventThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Loss of control in flight
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Destroyed
Cause areas
- Aircraft › Aircraft systems
Approximate · Coordinates from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
From the Wikipedia article
On September 4, 2022, a DHC-3 Turbine Otter single-engine floatplane on a passenger flight from Friday Harbor to Renton, Washington, U.S., crashed into the waters of Mutiny Bay near Whidbey Island, killing all ten people on board. The plane was operated by West Isle Air doing business as Friday Harbor Seaplanes, a service owned by Northwest Seaplanes.
Accident
The plane departed at 14:50 Pacific Daylight Time (21:50 UTC) from Friday Harbor and was en route to Renton Municipal Airport when reports of the crash came in at 15:11 PDT (22:11 UTC). Witnesses recalled a chaotic scene, with strong gasoline smells and said the impact "disintegrated" the airplane.
Before the plane crashed, Northwest Seaplanes noticed a slight shift in its direction compared to the flight plan and attempted to contact the pilot. Northwest Seaplanes called emergency responders after receiving no response, and soon after, witnesses called 911 to report that the plane had nosedived into the water at high speed.
Investigation and cause
Investigation
The National Transportation Safety Board (NTSB) opened an investigation into the crash and was joined by National Oceanic and Atmospheric Administration vessels in the search for wreckage. A side-scan sonar was deployed by the University of Washington Applied Physics Laboratory and discovered large debris 190 ft below the surface that were identified as being similar to the plane. The NTSB worked with the US Navy to recover the wreckage using an ROV and a recovery barge.
The aircraft had no flight data recorder nor a cockpit voice recorder, and was not required to carry them. It was, however, equipped with a Ground Proximity Warning System. It had just passed a 100-hour inspection before the crash. Further recovery efforts took place on September 26, 2022; this search resulted in most of the wreckage and multiple bodies being recovered.
On October 24, 2022, the NTSB released an update on its investigation, stating that the horizontal stabilizer actuator had separated into two pieces at a threaded assembly fitting, which could be a contributing factor to the crash. The NTSB said that the actuator lock ring was missing from the wreckage. On October 25, 2022, Viking Air issued a service letter requiring DHC-3 Otter operators to inspect the aircraft and verify that the lock ring is properly installed.
The following day, on October 26, 2022, the NTSB issued urgent safety recommendations to the FAA and Transport Canada urging all DHC-3 Otter operators to inspect the horizontal stabilizer actuator lock ring and report their findings to the respective agencies. The NTSB also recommended the immediate grounding of all DHC-3 seaplanes until further notice, citing concern that more will crash.
Final report
On September 29, 2023, the NTSB released its final report on the crash, stating that the probable cause was the loss of control of the plane due to the 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.
Text from the Wikipedia article “2022 Mutiny Bay DHC-3 crash” (revision 1339317888, retrieved 2026-09-18) by its authors, under CC BY-SA 4.0. Extracted as plain text: references, tables, images and some sections are left out. Read the article
NTSB narrative
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.
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.
Verbatim NTSB factual narrative and probable cause from the NTSB dataset
Sources
Wikipedia article: 2022 Mutiny Bay DHC-3 crash
- Article
- 2022 Mutiny Bay DHC-3 crash
- Revision
- 1339317888 · 2026-02-19 · retrieved 2026-09-18
- Wikidata
- Q114069721
- Licence
- Text CC BY-SA 4.0, by the article's authors; Wikidata CC0; town positions GeoNames (CC BY 4.0)
NTSB record DCA22MA193
- Event ID
- 20220905105855
- Case number
- DCA22MA193
- Dataset
- full-current
- Source SHA-256
- 5cf380f0061817c0331a6b2d8cc7e0ee3a79bea469a1001dc5c10e56f35f5ab3
Where each value comes from
- Record
- Wikipedia article "2022 Mutiny Bay DHC-3 crash" (page 71683052, revision 1339317888); merged with NTSB case DCA22MA193 (events / aircraft)
- Date
- NTSB record DCA22MA193: NTSB narrative opening date, consistent with the API date and time (local date)
- Place and country
- Wikipedia infobox: site; country from NTSB record DCA22MA193
- Map position
- NTSB record DCA22MA193: NTSB API eventLatitude/eventLongitude
- Aircraft, operator and route
- NTSB record DCA22MA193: aircraft; gaps from Wikipedia infobox: aircraft type, registration, operator, origin and destination; route airports from the linked airport articles' Wikidata codes (OurAirports)
- Operation
- NTSB record DCA22MA193: operated under Part 135: Air Taxi & Commuter
- Fatalities
- NTSB record DCA22MA193: NTSB API totalFatal
- Ground fatalities
- NTSB record DCA22MA193: NTSB API ongroundFatal
- Summary
- Wikipedia infobox: summary
Source notes (4)
- One occurrence in two sources, merged: the Wikipedia article "2022 Mutiny Bay DHC-3 crash" and NTSB case DCA22MA193, matched by the same aircraft registration and date. For this US event the NTSB's values are used where the two differ; each value names its source.
- Filled from the NTSB case API where the bulk record had no value: investigation status, coordinates, cause areas. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- Corrected after a review of the NTSB narrative, which states these values explicitly: destination. The narrative gives the intended destination as Will Rogers Wiley Post Memorial Seaplane Base (W36), Renton, not the land airport RNT.