40 Mile Air Cessna 207 accident
Cessna 207 · Accident: total loss of engine power (mechanical failure) en route
From Fairbanks International Airport (FAI) to HEALY LAKE, AK
Event
- NTSB case
- ANC00LA035
- 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
- N75703
- Operator
- 40 Mile Air
- Onboard fatalities
- Unknown
- Route
- From Fairbanks International Airport (FAI), Fairbanks, AKTo HEALY LAKE, 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
- Engine assembly, piston › Disintegrated
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The pilot stated that while in cruise at 5,500 feet msl, the engine began to run rough, and slowly lose power. The pilot attempted to reach an airport, but the engine lost total power. The airplane contacted trees and cartwheeled into an open field. Inspection of the engine revealed detonation and disintegration of the number two piston, and metal fouling of seven spark plugs. Bench testing of the fuel and ignition system revealed no discrepancies with the fuel distributor, lines, or nozzles; and no discrepancies with either magneto, magneto timing, or ignition harness. Manufacturer's service bulletin 91-8 recommends a time between overhaul (TBO) for the IO-520 of 1,700 hours. The engine had accumulated 1,560 hours since overhaul. The number two cylinder had been replaced 817 hours prior to the accident. All six cylinders had been replaced at different times within the previous 998 hours.
Probable cause
The disintegration of the number two piston. A factor in this accident was the subsequent metal fouling of the spark plugs, which resulted in total loss of engine power.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record ANC00LA035
- Event ID
- 20001212X20577
- Case number
- ANC00LA035
- 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: 7344c072940e887417d484e1b2a58d464a41f7124e01e8a74b2599681eec1e7a; retrieved 2026-09-18T16:46:24.717Z.