# NTSB CEN20LA345: Stinson 108, N9726K, Glenwood Springs, CO, August 12, 2020 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: August 12, 2020, 08:00 local (14:00 UTC) - Place: Glenwood Springs, CO - Coordinates: 39.508335, -107.31055 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=39.5083&lon=-107.3106&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing: Loss of control on ground](https://openairdocs.org/ntsb-events/230) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: FAA - NTSB case key (mKey): 101809 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN20LA345 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/101809/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=101809 - Page: https://openairdocs.org/ntsb/CEN20LA345 ## Probable cause The pilot’s loss of directional control upon landing due to a sheared tailwheel locking pin. ## 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 108-2, 13 cases](https://openairdocs.org/ntsb-findings/01062020/cases.md?model=9230406), [All aircraft, 3,958 cases](https://openairdocs.org/ntsb-findings/01062020/cases.md) - [Landing gear system: landing gear steering system](https://openairdocs.org/ntsb-findings/01023250): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [Stinson 108-2, 1 case](https://openairdocs.org/ntsb-findings/01023250/cases.md?model=9230406), [All aircraft, 32 cases](https://openairdocs.org/ntsb-findings/01023250/cases.md) - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Stinson 108-2, 14 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=9230406), [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: Loss of control on ground](https://openairdocs.org/ntsb-events/230) (defining event); cases with it: [Stinson 108-2, 13 cases](https://openairdocs.org/ntsb-events/230/sequence.md?model=9230406), [All aircraft, 4,585 cases](https://openairdocs.org/ntsb-events/230/sequence.md) ## Analysis According to the pilot, upon touchdown, the tailwheel equipped airplane immediately “lurched” right. He said that he tried to correct, and the airplane initially veered left; however, it ultimately veered right followed by a ground loop. The airplane sustained substantial damage to the left wing. The pilot stated that neither occupant was actuating the brakes at the time of the landing. A post-accident examination revealed that the tailwheel locking pin was sheared, which allowed the tailwheel to rotate freely more than 90°. When the pin is not engaged, the fork would have the ability to rotate and pivot independently of the steering arm and rudder input, a condition known as free-castoring. ## Factual narrative On August 12, 2020, about 0800 mountain daylight time, a Stinson 108, N9726K, was substantially damaged when it was involved in an accident near Glenwood Springs, Colorado. The pilot and the flight instructor were uninjured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the pilot, upon touchdown, the tailwheel equipped airplane immediately “lurched” right. He said that he tried to correct, and the airplane initially veered left; however, it ultimately veered right followed by a ground loop. The airplane sustained substantial damage to the left wing. The pilot stated that neither occupant was actuating the brakes at the time of the landing. A postaccident examination revealed that the tailwheel locking pin (item #8 in figure 1 below) was sheared, which allowed the tailwheel to rotate freely more than 90°. The locking pin, when properly functioning, locks the steering arm to the tailwheel fork assembly. When the pin is not engaged, the fork has the ability to rotate and pivot independently of the steering arm and rudder input, a condition known as free-castoring. Figure 1: Maule Tailwheel Schematic ## Aircraft - Registration: [N9726K](https://openairdocs.org/aircraft/N9726K), registered now, S/N 108-2726, built 1947 (OpenAirDocs) - Reported make and model: Stinson 108 (2) - Registry model: [Stinson 108-2](https://openairdocs.org/model/stinson-108-2) (registry code 9230406) (OpenAirDocs) - Registry engine: [Franklin 6A4165 series](https://openairdocs.org/engine/franklin-6a4165-series) (registry code 27025, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 108-2726 - Year built: 1947 - Airframe hours: 2326 - Engines: Continental O-470-R-25A 230 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, June 28, 2020 - Departed: KEGE, Eagle, CO - Destination: Same as departure - Airport: GWS, Glenwood Springs Muni, runway 14, 3,305 × 50 ft, asphalt - Equipment: ADS-B ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 72; injuries: none; airline transport; airplane ratings: single-engine land, multi-engine land, single-engine sea; instrument ratings: airplane; medical: class 1, without waivers/limitations; seat: left; flight hours: 18,800 total, 1 in this make and model, 9 in the last 90 days, 4 in the last 30 days - Flight instructor; age 73; injuries: none; airline transport, flight engineer, flight instructor; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; last flight review November 10, 2019; seat: right; restraint: 4-point; flight hours: 17,500 total, 1,160 in this make and model, 6,200 as pilot in command, 58 in the last 90 days, 18 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 230° at 11 knots, gusting 19 - Visibility: 10 statute miles - Lowest ceiling: 9,000 ft broken - Temperature: 54 °F, dew point 26 °F - Altimeter: 30.55 inHg - Observed at: K5SM, 6 nm away ## 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 20200812013739A](https://openairdocs.org/incident/20200812013739A), Aug 12, 2020: Stinson 108-2, Glenwood Spring, CO, Substantial damage. On August 12, 2020, the winds were calm with VFR conditions. The pilot made a three (3) point landing in the conventional gear aircraft. On rollout at about 20… ## Docket (5 files) The files NTSB released with the investigation on April 22, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=101809. 3.7 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 9 pages, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11653990&FileExtension=pdf&FileName=6120_Redacted-Rel.pdf - Pilot interview (item 2, PDF, 1 page, 288 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11653921&FileExtension=pdf&FileName=ROC_PIC-Rel.pdf - Examination email (item 3, PDF, 2 pages, 535 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11653672&FileExtension=pdf&FileName=PIC%20Email_Redacted-Rel.pdf - Tailwheel diagram (item 4, PDF, 1 page, 64 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11654306&FileExtension=pdf&FileName=Tailwheel%20Component%20Diagram-Rel.pdf - Photos (item 5, PDF, 3 pages, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11654391&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. --- 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.