CHI04LA256 · Claxton S-12
Claxton S-12 · Accident: loss of engine power en route
From Oconomowoc, WI (private airstrip) to Sylvania Airport (C89)
Event
- NTSB case
- CHI04LA256
- 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
- 1 · 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
- 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
Claxton S-12
- Aircraft type
- Claxton S-12
- 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
- UNREG
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Oconomowoc, WI (private airstrip)To Sylvania Airport (C89), Sturtevant, WI
- Aircraft age
- Not recorded
- 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
- En route · cruise
- First occurrenceThe 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
- 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
- Engine assembly, piston › Seized
- Pilot in command › Airspeed, not maintained
- Pilot in command › Spiral, inadvertent
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The un-registered airplane was destroyed when it impacted the ground following an engine failure after takeoff. The non-certificated pilot was fatally injured. A witness reported seeing the airplane and hearing the engine "quit". The airplane then made a series of gliding turns before it impacted into a marsh. The witness did not see the impact. Examination of the airplane showed no anomalies with respect to the airframe or control system. The engine's pistons exhibited scuffing and scoring indicative of a seizure. The marks on the piston contained carbon deposits indicating that the engine had experienced a seizure prior to the accident flight that had not been repaired.
Probable cause
The loss of engine power due to the seizure of the pistons and the pilot's failure to maintain airspeed which resulted in an inadvertent stall. The previous damage to the pistons due to earlier seizure occurrences was a factor.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CHI04LA256
- Event ID
- 20040923X01480
- Case number
- CHI04LA256
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
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: b3c5834df4f5c9c6b1f12646cec3b1cf985d2c35ef2051ab5c30e470a2db0804; retrieved 2026-09-20T18:20:31.608Z.