ANC21LA068 · Stinson 108-1
Stinson Aviation Stinson 108-1 · Accident: loss of engine power (partial) during initial climb
Event
- NTSB case
- ANC21LA068
- 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
- Unknown
- 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
- General aviation
- 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
Stinson 108-1
- Aircraft type
- Stinson 108
- 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
- N8656K
- Operator
- Stinson Aviation
- Onboard fatalities
- Unknown
- Route
- From not recordedTo not recorded
- Aircraft age
- About 74 years (built 1947)
- 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 91: General Aviation
- 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
- Initial climb
- 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 (partial)
- 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 from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
NTSB narrative
The pilot was conducting a local flight with friends onboard. He estimated the airplane’s takeoff weight to be about 76 lbs under maximum gross weight. The pilot stated that during the initial climb, the engine did not feel like it was producing full power and the airplane descended into trees, which resulted in substantial damage to the fuselage and wings.
A video of the takeoff and initial climb revealed that the sound of the engine was consistent throughout the length of the video with no audible anomalies noted. A windsock that was visible in the video showed a slight right-quartering tailwind at the time of the takeoff.
A postaccident examination revealed that the top spark plug from the No. 6 cylinder was mostly unscrewed and exhibited external signatures consistent with exposure to high heat, which indicated hot gas was leaking out of the cylinder through the spark plug hole. When the cylinders were checked for compression using the thumb check method, the Nos. 2 and 3 cylinders produced low compression.
It is likely that the loose spark plug in combination with the two weak cylinders resulted in the engine producing less than full power. Additionally, the pilot’s decision to takeoff with a slight right-quartering tailwind likely contributed to the airplane’s lack of climb performance.
Probable cause
Insufficient available power as a result of low compression in three engine cylinders. Contributing to the accident was the pilot’s decision to takeoff with a slight quartering tailwind.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record ANC21LA068
- Event ID
- 20210803103616
- Case number
- ANC21LA068
- 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, 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.
- API snapshot SHA-256: 3641b784862ca733d2f7fc02860cb42dbcff0abc7ce478112238e38b038c66b5; retrieved 2026-09-16T14:22:04.341Z.