SEA91LA036 · Beech D35
Beech D35 · Accident: in flight encounter with weather en route
From Helena Regional Airport (HLN) to St George Regional Airport (SGU)
Event
- NTSB case
- SEA91LA036
- 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
- Instrument Meteorological Cond
Beech D35
- Aircraft type
- Beechcraft 35
- 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
- N2911B
- Operator
- Ferguson, Michael D. · private individual
- Onboard fatalities
- Unknown
- Route
- From Helena Regional Airport (HLN), Helena, MTTo St George Regional Airport (SGU), ST GEORGE, UT
- 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
- In flight encounter with weather
- 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
- Fuel system, carburetor › Ice
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
DURING A CROSS COUNTRY FLIGHT, THE ENGINE BEGAN TO MISS AND EVENTUALLY LOST POWER. THE AIRPLANE WAS IN IMC WITH VISIBLE SNOW AND ICE CRYSTALS. AN EMERGENCY LANDING WAS MADE AT NIGHT IN AN OPEN/ROUGH FIELD AND THE AIRCRAFT WAS DAMAGED DURING THE LANDING ROLL. DURING A POST CRASH ENGINE INSPECTION, ICE WAS FOUND ABOVE THE THROTTLE VALVE AND BELOW THE DISCHARGE NOZZLE IN THE CENTER OF THE CARBURETOR THROAT AT THE INTAKE MANIFOLD. THE CARBURETOR WAS EQUIPPED WITH ALTERNATE AIR.
Probable cause
A LOSS OF ENGINE POWER DUE TO INDUCTION SYSTEM ICING. FACTORS RELATED TO THE ACCIDENT WERE: THE ADVERSE WEATHER CONDITION, AND A BLOCKED INDUCTION AIR FILTER.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record SEA91LA036
- Event ID
- 20001212X24826
- Case number
- SEA91LA036
- 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 1990-12-20.
- API snapshot SHA-256: 51ddecca2df7c3e106b4487975192240fe53a284867914d22cb35f6e3969175d; retrieved 2026-09-23T05:00:17.536Z.