Copper Valley Air Service Cessna U206C accident
Cessna U206C · Accident: loss of engine power (total) en route
From Gulkana Airport (GKN) to Mc Carthy Airport (15Z)
Event
- NTSB case
- ANC14LA040
- 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
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- Unknown
- 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
Cessna U206C
- Aircraft type
- Cessna 206
- 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
- N29137
- Operator
- Copper Valley Air Service
- Onboard fatalities
- Unknown
- Route
- From Gulkana Airport (GKN), GULKANA, AKTo Mc Carthy Airport (15Z), MCCARTHY, AK
- Aircraft age
- About 46 years (built 1968)
- 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 · cruise
- 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 engine power (total)
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Aircraft › Aircraft power plant
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
While in level cruise on the scheduled passenger flight, the airline transport pilot heard a loud "bang," followed by a quieter "bang" and a total loss of engine power. He conducted a forced landing to a densely-wooded area, during which the airplane nosed over, resulting in substantial damage to the wings and horizontal stabilizer. A visual examination of the engine revealed a crack in the crankcase. A subsequent examination of the No. 1 piston assembly revealed fatigue fractures in both connecting rod retaining bolts. Additional internal damage to the engine was found to be consistent with damage caused by the release of the connecting rod from the crankcase.
Probable cause
The failure of the engine’s No. 1 piston connecting rod retaining bolts due to fatigue, which resulted in a total loss of engine power during cruise flight.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record ANC14LA040
- Event ID
- 20140612X30848
- Case number
- ANC14LA040
- Dataset
- full-current
- Source SHA-256
- 5cf380f0061817c0331a6b2d8cc7e0ee3a79bea469a1001dc5c10e56f35f5ab3
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status. 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.
- API snapshot SHA-256: 98b50568b79ffd3abfc46a195a8e42d3f029d671a8013e8f1bd4e044a571cd04; retrieved 2026-09-16T00:04:51.366Z.