# NTSB ANC20LA098: Cessna 182, N182KT, King Salmon, AK, September 21, 2020 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: September 21, 2020, 14:05 local (22:05 UTC) - Place: King Salmon, AK - Coordinates: 58.672779, -156.6425 - Nearby events: https://openairdocs.org/map.md?lat=58.6728&lon=-156.6425&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-landing roll: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Alaska Regional Office - Parties: FAA - NTSB case key (mKey): 102032 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC20LA098 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/102032/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=102032 - Page: https://openairdocs.org/ntsb/ANC20LA098 ## Probable cause The fatigue fracture failure of the left main landing gear U-bolt during landing, which resulted in the collapse and separation of the left main landing gear spring. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Fuselage: gear attach fittings (on fus)](https://openairdocs.org/ntsb-findings/01035343): Aircraft › Aircraft structures · Fatigue/wear/corrosion (probable cause); cases with it: [Cessna 182A, 1 case](https://openairdocs.org/ntsb-findings/01035343/cases.md?model=2072704), [All aircraft, 16 cases](https://openairdocs.org/ntsb-findings/01035343/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: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [Cessna 182A, 1 case](https://openairdocs.org/ntsb-events/330/sequence.md?model=2072704), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) - [Landing-landing roll: Loss of control on ground](https://openairdocs.org/ntsb-events/230); cases with it: [Cessna 182A, 10 cases](https://openairdocs.org/ntsb-events/230/sequence.md?model=2072704), [All aircraft, 4,585 cases](https://openairdocs.org/ntsb-events/230/sequence.md) - [Landing-landing roll: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338); cases with it: [Cessna 182A, 4 cases](https://openairdocs.org/ntsb-events/338/sequence.md?model=2072704), [All aircraft, 563 cases](https://openairdocs.org/ntsb-events/338/sequence.md) ## Analysis The pilot reported that, after a normal touchdown in crosswind conditions, the left main landing gear (MLG) began to shake and rattle. The shaking continued and became more severe as the airplane continued its landing roll, and the airplane subsequently began to veer to the left and exited the runway. As the airplane came to rest, the MLG spring separated from the fuselage, resulting in substantial damage to the left horizontal stabilizer and elevator. A postaccident examination of the left MLG spring attach hardware fractured surfaces revealed that the left MLG U-bolt failed due to fatigue cracking and the MLG support bolt fractured within the shank due to shear loads. ## Factual narrative On September 21, 2020, about 1405 Alaska daylight time, a Cessna 182C airplane, N182KT, sustained substantial damage when it was involved in an accident near King Salmon, Alaska. The private pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the pilot, after a normal touchdown in crosswind conditions, the left main landing gear (MLG) began to shake and rattle. The shaking continued and became more severe as the airplane continued the landing roll, and the airplane subsequently began to veer to the left and exited the runway. As the airplane came to rest, the left MLG spring separated from the fuselage, resulting in substantial damage to the left horizontal stabilizer and elevator. An initial examination of the airplane by the pilot revealed that the left MLG spring U-bolt and MLG support bolt fractured, allowing the left MLG spring to separate from the fuselage. A visual and microscopic examination of the left MLG spring attach hardware revealed a fatigue crack in the U-bolt that emanated in the first thread root of the U-bolt and propagated substantially through the thickness of the thread until it reached a critical size and ultimately failed due to overstress. Examination of the MLG bolt revealed that the bolt fractured within the shank due to shear loads. ## Aircraft - Registration: [N182KT](https://openairdocs.org/aircraft/N182KT), registered now, S/N 51396 (OpenAirDocs) - Reported make and model: Cessna 182 (C) - Registry model: [Cessna 182A](https://openairdocs.org/model/cessna-182a) (registry code 2072704) (OpenAirDocs) - Registry engine: [Continental O-470 series](https://openairdocs.org/engine/continental-o-470-series) (registry code 17026, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 52854 - Year built: 1960 - Airframe hours: 6693 - Engines: Continental O-470 SERIES 230 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, December 5, 2019 - Departed: King Salmon, AK - Destination: Same as departure - Airport: PAKN, King Salmon, runway 12, 8,901 × 150 ft, asphalt - Equipment: Unknown ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 32; injuries: none; private; airplane ratings: single-engine land; medical: class 3, without waivers/limitations; last flight review October 25, 2018; seat: left; restraint: 3-point; flight hours: 391.4 total, 327.1 in this make and model, 328.3 as pilot in command, 117.2 in the last 90 days, 45.5 in the last 30 days, 2.6 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 80° at 15 knots, gusting 25 - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 57 °F, dew point 39 °F - Altimeter: 29.27 inHg - Observed at: PAKN, 1 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 20200921018569A](https://openairdocs.org/incident/20200921018569A), Sep 21, 2020: Cessna 182C, King Salmon, AK, Substantial damage. Pilot selected rwy 12 for crosswind landing. Landing was made and left gear separated from the aircraft on rollout. Pilot held aft elevator to maintain… ## Docket (4 files) The files NTSB released with the investigation on January 14, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=102032. 68.9 MB in all. - Materials laboratory factual report 20-057 (item 1, PDF, 9 pages, 7 photos, 3.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11711140&FileExtension=pdf&FileName=Materials%20Laboratory%20Factual%20Report%2020-057-Rel.pdf - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 2, PDF, 7 pages, 63.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11715383&FileExtension=pdf&FileName=6120_Redacted-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 3, PDF, 2 pages, 186 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13115812&FileExtension=pdf&FileName=Release_Redacted-Rel.pdf - Photos (courtesy of king salmon airport operations) (item 4, PDF, 2 pages, 2.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11714994&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.