SEA97LA152 · Cessna 172A
Cessna 172A · Accident: partial loss of engine power (mechanical failure) en route
From Ogden Hinckley Airport (OGD) to an unrecorded destination
Event
- NTSB case
- SEA97LA152
- 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
- 0
- 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
Cessna 172A
- Aircraft type
- Cessna 172
- 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
- N6844X
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Ogden Hinckley Airport (OGD), UTTo not recorded
- 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
- Partial loss of engine power (mechanical failure)
- 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
- Engine assembly, valve, exhaust › Fractured
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
About 30 minutes after takeoff, the engine began to run rough and lose power. The first pilot (pilot-in-command) attempted to regain full power and return to the departure airport. The airplane continued to descend and the first pilot attempted to land in a hayfield about four miles from the airport. During the forced landing, which occurred in a tailwind, the pilot noticed power lines ahead. He forced the airplane onto rough terrain beneath the power lines. The airplane nosed over on landing and was substantially damaged. An examination of the engine revealed that the exhaust valve stem on the no. 4 cylinder had separated from the valve head. The fracture surface was obliterated and the mode of failure could not be determined. After the failure of the valve, further damage to other cylinder components subsequently occurred as the engine continued to operate in a degraded condition. The no. 4 cylinder had been reworked about 108 flight hours prior to the accident.
Probable cause
The fracture of the no. 4 exhaust valve and subsequent loss of engine power. Factors contributing to the accident include a congested landing area, and rough terrain.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record SEA97LA152
- Event ID
- 20001208X08267
- Case number
- SEA97LA152
- 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: 0e6ef8e297212e863af6db9f8e503f942c05b836f6d7ace07682f9fc6997123c; retrieved 2026-09-21T21:24:25.219Z.