# NTSB ANC21LA086: Stinson 108-3, N6476M, Port Alsworth, AK, September 12, 2021

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Class 3 · Limited · Final report
- Date: September 12, 2021, 09:00 local (17:00 UTC)
- Place: Port Alsworth, AK
- Coordinates: 60.2, -154.32
- Nearby events: https://openairdocs.org/map.md?lat=60.2000&lon=-154.3200&mi=10
- Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping)
- Defining event: [Landing-landing roll: Loss of control on ground](https://openairdocs.org/ntsb-events/230)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed
- Report: Approved by Office Director
- Investigation class: Class 3
- NTSB office: Alaska Regional Office
- Parties: Federal Aviation Administration (FAA)
- NTSB case key (mKey): 103847
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC21LA086
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/103847/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=103847
- Page: https://openairdocs.org/ntsb/ANC21LA086

## Probable cause

A loss of directional control for reasons that could not be determined based on the available information.

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Landing gear system: brake](https://openairdocs.org/ntsb-findings/01023242): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [Stinson 108-3, 2 cases](https://openairdocs.org/ntsb-findings/01023242/cases.md?model=9230408), [All aircraft, 297 cases](https://openairdocs.org/ntsb-findings/01023242/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Landing-landing roll: Loss of control on ground](https://openairdocs.org/ntsb-events/230) (defining event); cases with it: [Stinson 108-3, 12 cases](https://openairdocs.org/ntsb-events/230/sequence.md?model=9230408), [All aircraft, 4,585 cases](https://openairdocs.org/ntsb-events/230/sequence.md)

## Analysis

The pilot reported that, during the landing roll while applying the brakes, the right brake “went flat.” The airplane veered to the left, impacted a stump, and nosed over, resulting in substantial damage to the fuselage and left wing. A postaccident examination revealed no mechanical anomalies with the brake system that would have precluded normal operation. Based on the available information, the reason for the loss of control during landing could not be determined.

## Factual narrative

On September 12, 2021, about 0900 Alaska daylight time, a Stinson 108-3, N6476M, was substantially damaged when it was involved in an accident near Port Alsworth, Alaska. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that, during the landing roll while applying the brakes, the right brake “went flat.” The airplane veered to the left, impacted a stump, and nosed over, resulting in substantial damage to the fuselage and left wing. A postaccident examination revealed no mechanical anomalies with the brake system that would have precluded normal operation.

## Aircraft

- Registration: [N6476M](https://openairdocs.org/aircraft/N6476M), registered now, S/N 108-4476, built 1948 (OpenAirDocs)
- Reported make and model: STINSON 108-3
- Registry model: [Stinson 108-3](https://openairdocs.org/model/stinson-108-3) (registry code 9230408) (OpenAirDocs)
- Registry engine: [Franklin 6A4165 series](https://openairdocs.org/engine/franklin-6a4165-series) (registry code 27025, reciprocating) (OpenAirDocs)
- Category: Airplane
- Serial number: 108-4476
- Year built: 1948
- Airframe hours: 2729.6
- Engines: Continental O-470-S 230 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, June 25, 2021
- Destination: Same as departure
- Airport: PVT, Pvt, runway PVT, 720 × 50 ft, gravel
- Equipment: None

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 30; injuries: none; flight instructor, commercial; airplane ratings: single-engine sea, single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review April 12, 2021; seat: left; restraint: lap only; flight hours: 5,006.2 total, 33 in this make and model, 4,796.1 as pilot in command, 350.3 in the last 90 days, 104.6 in the last 30 days

## Weather

- Conditions: Visual (VMC), Day
- Wind: 70° at 8 knots
- Visibility: 30 statute miles
- Lowest ceiling: 8,000 ft broken
- Temperature: 54 °F, dew point 45 °F
- Altimeter: 29.58 inHg
- Observed at: PALJ
- METAR: PALJ 121653Z 07008KT 30SM BKN080 OVC120 12/07 A2958 RMK EST PASS OPN NOSPECI

## Docket (4 files)

The files NTSB released with the investigation on January 31, 2023, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=103847. 6.1 MB in all.

- Materials laboratory factual report (item 1, PDF, 8 pages, 10 photos, 4.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12836705&FileExtension=pdf&FileName=21-080%20-%20Materials%20Lab%20Factual%20Report%20(ANC21LA086)-Rel.pdf
- Pilot/operator aircraft accident report, NTSB form 6120.1 (item 2, PDF, 9 pages, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12783136&FileExtension=pdf&FileName=6120%20dms_Redacted-Rel.pdf
- Wreckage examination email (item 3, PDF, 1 page, 115 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12856222&FileExtension=pdf&FileName=Exam%20Email_Redacted-Rel.pdf
- Photos (item 4, PDF, 2 pages, 129 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12856088&FileExtension=pdf&FileName=Photo%20Array-Rel.pdf

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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