# NTSB WPR21LA289: Stinson 108-1, N8844K, Bozeman, MT, July 25, 2021 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Class 4 · Limited · Final report - Date: July 25, 2021, 13:44 local (19:44 UTC) - Place: Bozeman, MT · Airport Environment - runway - Coordinates: 45.777236, -111.15026 - Nearby events: https://openairdocs.org/map.md?lat=45.7772&lon=-111.1503&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: Minor injuries - Injuries: 2 minor - Status: Completed - Report: Approved by Office Director - Investigation class: Class 4 - Basic report with no Prelim publish - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 103566 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR21LA289 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/103566/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=103566 - Page: https://openairdocs.org/ntsb/WPR21LA289 ## Probable cause The pilot’s failure to maintain directional control during landing which resulted in a ground loop. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Performance/control parameters: directional control](https://openairdocs.org/ntsb-findings/01062020): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Stinson 108-1, 10 cases](https://openairdocs.org/ntsb-findings/01062020/cases.md?model=9230404), [All aircraft, 3,958 cases](https://openairdocs.org/ntsb-findings/01062020/cases.md) - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot; cases with it: [Stinson 108-1, 10 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=9230404), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/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 108-1, 13 cases](https://openairdocs.org/ntsb-events/230/sequence.md?model=9230404), [All aircraft, 4,585 cases](https://openairdocs.org/ntsb-events/230/sequence.md) - [Landing-landing roll: Runway excursion](https://openairdocs.org/ntsb-events/300); cases with it: [Stinson 108-1, 6 cases](https://openairdocs.org/ntsb-events/300/sequence.md?model=9230404), [All aircraft, 3,643 cases](https://openairdocs.org/ntsb-events/300/sequence.md) ## Analysis The pilot in the tailwheel-equipped airplane reported that, he made a normal wheel landing and as he was about to lower the tailwheel, the airplane veered to the right. He attempted to correct with left rudder control, but the airplane ground looped. The pilot opined that the airplane may have been caught by a wind gust, which started an oscillation that he was not able to correct for. The airplane sustained substantial damage to the left wing and lift strut. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operations. ## Aircraft - Registration: [N8844K](https://openairdocs.org/aircraft/N8844K), registered now, S/N 108-1844, built 1947 (OpenAirDocs) - Reported make and model: STINSON 108-1 - Registry model: [Stinson 108-1](https://openairdocs.org/model/stinson-108-1) (registry code 9230404) (OpenAirDocs) - Registry engine: [Franklin 6A4150 series](https://openairdocs.org/engine/franklin-6a4150-series) (registry code 27024, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 108-1844 - Year built: 1947 - Engines: Franklin 6A4-150-B3 150 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal; Standard, Utility - Departed: S83, Shoshone, ID - Destination: Same as departure - Airport: BZN, Bozeman Yellowstone Intl, runway 12/30, 8,994 × 150 ft, asphalt - Equipment: ADS-B, Electronic flight bag or handheld device ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 36; injuries: none; private; airplane ratings: single-engine land; medical: class 3, without waivers/limitations; last flight review September 1, 2020; seat: left; restraint: 4-point; flight hours: 109 total, 66 in this make and model, 70 as pilot in command, 25 in the last 90 days, 11 in the last 30 days, 7 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 340° at 3 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 84 °F, dew point 37 °F - Altimeter: 30.10 inHg - Observed at: KBZN, 1 nm away - METAR: KBZN 251856Z 34003KT 10SM CLR 29/03 A3010 RMK AO2 SLP153 T02940033 ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20210725011829A](https://openairdocs.org/incident/20210725011829A), Jul 25, 2021: Stinson 108-1, Boseman, MT, Substantial damage. On landing, pilot experienced right drift due to un anticipated/forecasted wind and was unable to retain control of aircraft and maintain runway alignment.… ## Docket (2 files) The files NTSB released with the investigation on October 12, 2021, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=103566. 2.6 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 9 pages, 2.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12762439&FileExtension=pdf&FileName=WPR21LA289%206120_Redacted-Rel.pdf - Photo (pilot) (item 2, PDF, 1 page, 337 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12762768&FileExtension=pdf&FileName=Photos%20(Pilot)-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. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.