# NTSB WPR23LA226: Cessna 310I, N6PK, Sunnyside, WA, May 25, 2023 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: May 25, 2023, 12:45 local (19:45 UTC) - Place: Sunnyside, WA - Coordinates: 46.327072, -119.97036 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=46.3271&lon=-119.9704&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-landing roll: Landing gear collapse](https://openairdocs.org/ntsb-events/094) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: FAA - NTSB case key (mKey): 192361 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR23LA226 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/192361/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=192361 - Page: https://openairdocs.org/ntsb/WPR23LA226 ## Probable cause The failure of the side brace lock assembly of the right main landing gear due to overstress as a result of a hard landing. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Landing gear system: main landing gear](https://openairdocs.org/ntsb-findings/01023210): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [Cessna 310I, 1 case](https://openairdocs.org/ntsb-findings/01023210/cases.md?model=2074224), [All aircraft, 241 cases](https://openairdocs.org/ntsb-findings/01023210/cases.md) - [Landing gear system: main landing gear](https://openairdocs.org/ntsb-findings/01023210): Aircraft › Aircraft systems · Capability exceeded (probable cause); cases with it: [Cessna 310I, 1 case](https://openairdocs.org/ntsb-findings/01023210/cases.md?model=2074224), [All aircraft, 241 cases](https://openairdocs.org/ntsb-findings/01023210/cases.md) - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Cessna 310I, 1 case](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=2074224), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md) - [Performance/control parameters: landing flare](https://openairdocs.org/ntsb-findings/01062041): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Cessna 310I, 1 case](https://openairdocs.org/ntsb-findings/01062041/cases.md?model=2074224), [All aircraft, 1,285 cases](https://openairdocs.org/ntsb-findings/01062041/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Landing: Hard landing](https://openairdocs.org/ntsb-events/092); cases with it: [Cessna 310I, 2 cases](https://openairdocs.org/ntsb-events/092/sequence.md?model=2074224), [All aircraft, 2,102 cases](https://openairdocs.org/ntsb-events/092/sequence.md) - [Landing-landing roll: Landing gear collapse](https://openairdocs.org/ntsb-events/094) (defining event); cases with it: [Cessna 310I, 3 cases](https://openairdocs.org/ntsb-events/094/sequence.md?model=2074224), [All aircraft, 1,787 cases](https://openairdocs.org/ntsb-events/094/sequence.md) - [Landing-landing roll: Runway excursion](https://openairdocs.org/ntsb-events/300); cases with it: [Cessna 310I, 1 case](https://openairdocs.org/ntsb-events/300/sequence.md?model=2074224), [All aircraft, 3,643 cases](https://openairdocs.org/ntsb-events/300/sequence.md) ## Analysis The pilot reported that while on final approach he extended the gear, and a green light illuminated signifying that the gear was down. The landing was “firm” and, shortly after touchdown, the airplane’s right main landing gear slowly collapsed, causing the right wing to drop. The airplane veered to the right, exited the runway, and came to rest in a field about 100 ft from the runway centerline. During the accident sequence, the airplane sustained substantial damage to the right horizontal stabilizer and elevator. Postaccident examination of the right main landing gear fracture surface revealed that the side brace lock assembly likely fractured due to excessive axial compression loads that resulted in a ductile overstress fracture. Additionally, the bent side brace lock assembly attachment bolt at the lower end of the lock link also indicated that the loads associated with the failure of the attachment pin exceeded the design axial loads for the side brace lock assembly and were consistent with overload of the side brace lock assembly. The bearings and pin that attached the side brace lock to the lower end of the bellcrank, which were not recovered, were likely fractured as a result of the loads. The damage to the gear indicated that it likely failed as a result of the hard landing. ## Factual narrative On May 25, 2023, about 1245 Pacific daylight time, a Cessna 310I airplane, N6PK, was substantially damaged when it was involved in an accident near Sunnyside, Washington. 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 the final approach for landing was normal and after the gear handle was lowered he got a green light signifying that the gear was down. The landing was “firm” and, shortly after touchdown, the airplane’s right main landing gear slowly collapsed, causing the right wing to drop. Subsequently, the airplane veered to the right and exited the runway. The airplane came to rest in a field adjacent to the runway, about 100 ft from the runway centerline. During the accident sequence, the airplane sustained substantial damage to the right horizontal stabilizer and elevator. Postaccident examination of the right main landing gear revealed that the side brace lock assembly of the left main landing gear had separated. The lock assembly was sent to the National Transportation Safety Board Material’s laboratory for examination. Examination revealed that the forward lug of the clevis at the lower end of the bellcrank was fractured and the other lug remained intact. The mating side of the fractured lug, the bearings, and pin that attached the side brace lock to the lower end of the bellcrank were not recovered. The fracture surface had a rough matte appearance that was consistent with a ductile overstress fracture. Additionally, a portion of the fracture surface had smearing damage on the aft side that was consistent with sliding contact with the side brace lock link. On the intact lug, the inboard forward portion of the hole was deformed. The attachment bolt at the lower end of the left main landing gear side brace lock assembly was bent downwards. The lock link deformation and the bent bolt attaching the lock link to the side brace were consistent with axial compression loads on the assembly. A brownish black object was observed in the inboard side of the attachment pin hole, consistent with the set screw for the retaining pin that attached the bellcrank to the lock link. The area surrounding the attachment pin hole was deformed with a curved shape consistent with contact with the lower end of the missing bellcrank flange after being displaced downward relative to the lock link (these areas are normally not in contact in an intact assembly). ## Aircraft - Registration: [N6PK](https://openairdocs.org/aircraft/N6PK), registered now, S/N 310I0021, built 1964 (OpenAirDocs) - Reported make and model: CESSNA 310I - Registry model: [Cessna 310I](https://openairdocs.org/model/cessna-310i) (registry code 2074224) (OpenAirDocs) - Registry engine: [Continental I0-470 series](https://openairdocs.org/engine/continental-i0-470-series) (registry code 17027, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 310I0021 - Year built: 1964 - Airframe hours: 5695 - Engines: Continental IO-520-E 285 horsepower reciprocating; Continental IO-520-E 285 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, September 1, 2022 - Departed: MWH, Moses Lake, WA - Destination: Same as departure - Airport: 1S5, Sunnyside Municipal Airport, runway 25, 3,425 × 60 ft, asphalt - Equipment: ADS-B ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 76; injuries: none; airline transport, flight instructor; airplane ratings: single-engine sea, multi-engine land, multi-engine sea; instrument ratings: airplane; medical: class 2, with waivers/limitations; seat: left; restraint: lap only; flight hours: 12,628 total, 250 in this make and model, 15 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 120° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 73 °F, dew point 43 °F - Altimeter: 29.90 inHg - Observed at: KYKM, 27 nm away - METAR: METAR KYKM 251953Z AUTO 12005KT 10SM FEW075 FEW090 23/06 A2990 RMK AO2 SLP120 T02330061 ## Docket (2 files) The files NTSB released with the investigation on November 14, 2024, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=192361. 3.1 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 2.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16509956&FileExtension=pdf&FileName=NSTB%206120%20Final_Redacted-Rel.pdf - Materials laboratory factual report 23-096 (item 2, PDF, 7 pages, 5 photos, 939 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16511446&FileExtension=pdf&FileName=23-096-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.