ANC99LA082 · Maule M-4-220C
Maule M-4-220C · Accident: partial loss of engine power (mechanical failure) en route
From Willow Airport (UUO) to McGrath Airport (MCG)
Event
- NTSB case
- ANC99LA082
- 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
Maule M-4-220C
- Aircraft type
- Maule M-4
- 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
- N40677
- Operator
- Walt Warner
- Onboard fatalities
- Unknown
- Route
- From Willow Airport (UUO), Willow, AKTo McGrath Airport (MCG), 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 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, connecting rod › Fractured
- Engine assembly, cylinder › Separation
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The airline transport pilot reported that about 15 minutes after departure, the engine began to run rough, and lose power. He said that while performing the engine emergency procedures, he smelled smoke in the cabin, and he selected a forced landing area on a river bank bordered by trees. During the landing roll, the airplane's left wing collided with a stand of trees, the airplane pivoted 180 degrees to the left, and the left main landing gear collapsed. The airplane sustained substantial damage to the wings, fuselage, and empennage. An FAA airworthiness inspector from the Anchorage Flight Standards District Office, examined the airplane wreckage on June 24th. The inspector reported that the top portion of the number four engine cylinder was separated between the cylinder barrel and the cylinder head, and added that the piston connecting rod was fractured.
Probable cause
A separation of the number 4 engine cylinder, and a fracture of the number 4 engine connecting rod.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record ANC99LA082
- Event ID
- 20001212X18919
- Case number
- ANC99LA082
- 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: b5a07ba97b23ab3da7b5436cd770035245bab0fbf813adfeaf6367abe79d7dfd; retrieved 2026-09-22T14:46:24.864Z.