# NTSB WPR21LA337: Cessna 172E, N3965S, Enterprise, OR, September 2, 2021 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: September 2, 2021, 11:30 local (18:30 UTC) - Place: Enterprise, OR - Coordinates: 45.424547, -117.26465 - Nearby events: https://openairdocs.org/map.md?lat=45.4245&lon=-117.2647&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-flare/touchdown: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 103807 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR21LA337 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/103807/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=103807 - Page: https://openairdocs.org/ntsb/WPR21LA337 ## Probable cause The fatigue fracture of the nose gear upper torque link, which resulted in the separation of the torque link from the shock strut and a loss of directional control. ## 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 · Attain/maintain not possible (probable cause); cases with it: [Cessna 172E, 3 cases](https://openairdocs.org/ntsb-findings/01062020/cases.md?model=2072412), [All aircraft, 3,958 cases](https://openairdocs.org/ntsb-findings/01062020/cases.md) - [Landing gear system: nose/tail landing gear](https://openairdocs.org/ntsb-findings/01023220): Aircraft › Aircraft systems · Fatigue/wear/corrosion (probable cause); cases with it: [Cessna 172E, 1 case](https://openairdocs.org/ntsb-findings/01023220/cases.md?model=2072412), [All aircraft, 185 cases](https://openairdocs.org/ntsb-findings/01023220/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Landing-flare/touchdown: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [Cessna 172E, 1 case](https://openairdocs.org/ntsb-events/330/sequence.md?model=2072412), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) ## Analysis During landing, when the nose gear contacted the runway, the airplane immediately veered to the right, exited the runway surface, nosed over, and came to rest inverted. Postaccident examination of the airplane revealed that the nose gear upper torque link had fractured near the shock strut mount and separated from the shock strut, which resulted in a loss of directional control. Metallurgical examination of the fracture surfaces of the upper torque link revealed signatures consistent with a fatigue fracture. ## Factual narrative On September 2, 2021, about 1130 Pacific daylight time, a Cessna 172E airplane, N3965S, was substantially damaged when it was involved in an accident near Enterprise, Oregon. The pilot and passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that following a light touchdown on the center of runway 30, the airplane rolled smoothly on its main wheels for a couple of seconds. As the airplane slowed and the nose wheel engaged the ground, the airplane veered to the left, and the nose gear fully collapsed. He pushed the right rudder and applied full brakes to the right wheel. The airplane exited the runway, nosed over, and came to rest inverted. Examination of the airplane by a Federal Aviation Administration inspector revealed that the airplane sustained substantial damage to the fuselage, vertical stabilizer, and rudder. The nose gear upper torque link was separated from the shock strut. A section of the upper torque link remained attached to the shock strut. The two sections of the upper torque link were removed and sent to the National Transportation Safety Board Materials Laboratory for further examination. (See figure 1.) Figure 1. Photo showing the lower and upper torque link. The red arrow points to the fracture. Flat areas were observed at the forward ribs on the fracture surface of the upper torque link. The flat areas emanated from the forward edge of the ribs and extended almost until the transition from the ribs to the web of the upper torque link. The fracture surface of the cleaned upper torque link was examined using a scanning electron microscope. Within the flat areas on the fracture surface transgranular features consistent with fatigue cracking were observed. Outside the flat areas the fracture surface features were consistent with dimpled rupture from overstress. No specific entries pertaining to the nose gear torque links were observed in the airframe logbook. ## Aircraft - Registration: [N3965S](https://openairdocs.org/aircraft/N3965S), registered now, S/N 17251165, built 1964 (OpenAirDocs) - Reported make and model: CESSNA 172E - Registry model: [Cessna 172E](https://openairdocs.org/model/cessna-172e) (registry code 2072412) (OpenAirDocs) - Registry engine: [Continental 0-300 series](https://openairdocs.org/engine/continental-0-300-series) (registry code 17022, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 17251165 - Year built: 1964 - Airframe hours: 4151.52 - Engines: Continental O-300D 145 hp reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Jepsen William R Trustee - Registered owner: Jepsen William R Trustee - Airworthiness certificate: Standard, Normal - Last inspection: Annual, December 31, 2020, 35.7 hours before - Departed: OR8, Dug Bar, OR - Destination: Same as departure - Airport: 8S4, Enterprise Municipal Airport, runway 30, 2,850 × 50 ft, asphalt - Equipment: Handheld GPS, ADS-B ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 66; injuries: none; private; airplane ratings: single-engine land; medical: basicmed, with waivers/limitations; last flight review November 12, 2020; seat: left; restraint: 4-point; flight hours: 932 total, 880 in this make and model, 855 as pilot in command, 22 in the last 90 days, 6 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 64 °F, dew point 27 °F - Altimeter: 30.10 inHg - Observed at: KJSY, 4 nm away - METAR: KJSY 021835Z AUTO 00000KT 10SM CLR 18/M03 A3010 RMK AO2 T01821034 ## 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 20210902015229A](https://openairdocs.org/incident/20210902015229A), Sep 2, 2021: Cessna 172E, Enterprise, OR, Substantial damage. On landing rollout, the pilot reported the aircraft veered sharply to the left leaving the runway flipping over and coming to rest upside down causing… ## Docket (5 files) The files NTSB released with the investigation on February 28, 2023, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=103807. 12.2 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=12683363&FileExtension=pdf&FileName=NTSB%20Form%206120_1%20WPR21LA337_Redacted-Rel.pdf - Materials laboratory report on the upper torque link (item 2, PDF, 11 pages, 3.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14843324&FileExtension=pdf&FileName=22-096%20Materials%20Laboratory%20Factual%20Report%20(WPR21LA337)-Rel.pdf - Photos (item 3, PDF, 3 pages, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14844255&FileExtension=pdf&FileName=Photos%20for%20WPR21LA337-Rel.pdf - Pilot's statement (item 4, PDF, 2 pages, 116 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14844372&FileExtension=pdf&FileName=Pilto%20Statement%20to%20FAA_Redacted-Rel.pdf - Maintenance records (item 5, PDF, 12 pages, 4.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14886243&FileExtension=pdf&FileName=3965S%20Logs_Redacted-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.