SEA93LA055 · Boeing A75N1
Boeing A75N1 · Accident: total loss of engine power (mechanical failure) en route
From Southwest Wyoming Regional Airport (RKS) to Laramie Regional Airport (LAR)
Event
- NTSB case
- SEA93LA055
- 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
- Unknown
Boeing A75N1
- Aircraft type
- Boeing A75
- 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
- N56924
- Operator
- Denton, Larry E. · private individual
- Onboard fatalities
- Unknown
- Route
- From Southwest Wyoming Regional Airport (RKS), Rock Springs, WYTo Laramie Regional Airport (LAR), Laramie, WY
- 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
- Total 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, rocker arm/tappet › Failure, total
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
THE PILOT REPORTED THAT SHORTLY AFTER LEVELLING OFF AT 14,000 FEET MSL, THE ENGINE SURGED THREE TIMES AND THEN STOPPED. A FORCED LANDING WAS EXECUTED ONTO ROCKY, UPSLOPING TERRAIN, UNDER DARK NIGHT CONDITIONS. SUBSEQUENT DISASSEMBLY OF THE ENGINE REVEALED THAT THE NUMBER 7 CYLINDER INTAKE VALVE ROCKER ARM HAD FAILED.
Probable cause
FAILURE OF THE #7 CYLINDER ROCKER ARM. FACTORS CONTRIBUTING TO THE ACCIDENT WERE UNSUITABLE TERRAIN AND DARK NIGHT CONDITIONS.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record SEA93LA055
- Event ID
- 20001211X11759
- Case number
- SEA93LA055
- 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: local date, investigation status. Values present in the bulk record are kept.
- The date is the local date; the NTSB stores the UTC date 1993-01-20.
- API snapshot SHA-256: ff864a9cf7d7902502eaa8965d23071207fd76eb00b767dd7aad21056d865ed8; retrieved 2026-09-21T23:02:50.332Z.