Inland Aviation Services Cessna 207 accident
Cessna 207 · Accident: total loss of engine power (mechanical failure) en route
From Grayling Airport (KGX) to Bethel Airport (BET)
Event
- NTSB case
- ANC98LA078
- 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
- Charter & commuter
- 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 207
- Aircraft type
- Cessna 207
- 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
- N1673U
- Operator
- Inland Aviation Services
- Onboard fatalities
- Unknown
- Route
- From Grayling Airport (KGX), GRAYLING, AKTo Bethel Airport (BET), Bethel, AK
- 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 135: Air Taxi & Commuter
- 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)
- Also codedOther events the NTSB coded in the sequence, such as a wire strike after a loss of power. Flight Findings uses them for its kinds of event. Glossary
- Tree(s)
- 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
- Company maintenance personnel › Maintenance, installation, improper
- Engine assembly, crankcase › Undertorqued
- Engine assembly, crankshaft › Fractured
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The pilot and three passengers, departed on an air taxi flight over remote terrain. While in cruise flight about 2,200 feet, the engine oil pressure began to drop, and the engine oil temperature began to rise. The pilot decided to divert to the nearest airport. The engine quit running, and the pilot selected an emergency landing area on a sand bar along a river that contained several willow trees. During the landing, the airplane received damage to the wings and fuselage. The engine had accrued 1,491 hours since an overhaul. During that time, seven engine cylinder changes were performed by company maintenance personnel. An examination of the engine revealed the crankshaft was broken along the aft, lower edge of the number two cheek journal, at the forward radius of the number two main bearing journal. The fracture line was straight and flat, through the full dimension of the number two cheek journal, and was oriented perpendicular to the longitudinal axis of the crankshaft. The number two main bearing was broken and flattened. The number two main bearing saddle was flattened and distorted. The left and right engine case halves mating surface exhibited galling/fretting at the number two main journal bolt holes.
Probable cause
The improper installation/undertorquing of the engine crankcase bolts by company maintenance personnel, and a subsequent fracture of the engine crankshaft. A factor in the accident was unsuitable terrain for a forced landing.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record ANC98LA078
- Event ID
- 20001211X10216
- Case number
- ANC98LA078
- 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 1998-06-20.
- API snapshot SHA-256: d9fe229a845cd2dc6b0b8054d43a88df3ddc2a00de53e8add9767e341a76b864; retrieved 2026-09-18T17:07:51.025Z.