# NTSB ANC22LA040: Cessna U206F, N592KB, Kodiak, AK, June 8, 2022 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: June 8, 2022, 11:34 local (19:34 UTC) - Place: Kodiak, AK - Coordinates: 58.45173, -154.0743 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=58.4517&lon=-154.0743&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-flare/touchdown: Aircraft structural failure](https://openairdocs.org/ntsb-events/337) - Highest injury: No injuries - Injuries: 5 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Alaska Regional Office - Parties: FAA - NTSB case key (mKey): 105232 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC22LA040 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/105232/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=105232 - Page: https://openairdocs.org/ntsb/ANC22LA040 ## Probable cause The failure of the right main landing gear leg due to fatigue cracks that initiated from corrosion pitting. ## 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 · Fatigue/wear/corrosion (probable cause); cases with it: [Cessna U206F, 2 cases](https://openairdocs.org/ntsb-findings/01023210/cases.md?model=2073333), [All aircraft, 241 cases](https://openairdocs.org/ntsb-findings/01023210/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: Aircraft structural failure](https://openairdocs.org/ntsb-events/337) (defining event); cases with it: [Cessna U206F, 1 case](https://openairdocs.org/ntsb-events/337/sequence.md?model=2073333), [All aircraft, 290 cases](https://openairdocs.org/ntsb-events/337/sequence.md) ## Analysis The airplane was the fourth air tour company airplane to land at a remote beach site as part of a bear viewing flight. The pilot set up for a landing on the same tracks as the three previous company airplanes. During the landing, the left main landing gear wheel touched down first, followed by the right main landing gear wheel. When the right wheel touched down, the pilot heard a “pop” sound and the airplane veered to the right. The airplane slowly came to rest upright and sustained substantial damage to the left wing and right horizontal stabilizer. Postaccident examination revealed that the right main landing gear leg was fractured near the wheel attachment fitting. Materials laboratory examination of the right main landing gear leg revealed that the gear leg fractured during landing due to fatigue cracks that initiated from localized corrosion pitting. The area of the fatigue cracks which was absent paint and primer, contained many elements typical of salt corrosion in a marine environment. Repeated abrasive wear from landings on rough terrain or runway asphalt had likely removed the protective coatings in the area of the fatigue cracks. ## Factual narrative On June 8, 2022, about 1134 Alaska daylight time, a Cessna U206F, N592KB, was substantially damaged when it was involved in an accident 65 miles west-northwest of Kodiak, Alaska. The pilot and four passengers were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 135 air tour flight. According to the pilot, the airplane that he was flying was the fourth company airplane to land at a remote beach site, known as Hallo Bay, as part of a bear viewing flight. The pilot set up for a landing on the same tracks as the three preceding company airplanes. During the landing, the left main landing gear wheel touched down first, followed by the right main landing gear wheel. When the right wheel touched down, the pilot heard a “pop” sound and the airplane veered to the right. The airplane slowly came to rest upright about 150 ft from the initial touchdown location (see figure 1). The pilot reported that small leaves and seaweed debris were present in the landing area and that no large debris was noted. Figure 1. Accident airplane in its resting location (Source: K Bay Air). Postaccident examination of the airplane revealed substantial damage to the left wing and right horizontal stabilizer. The right main landing gear leg was fractured near the wheel attachment fitting and displayed fatigue signatures (see figure 2.). Figure 2. Fractured right main landing gear leg (Source: K Bay Air). A review of the airplane’s records revealed that, in July 2019, the main landing gear legs were removed and repaired per the manufacturer’s service manual. Between the time of repair and the accident, the main landing gear legs accumulated about 875 hours and about 200 beach/off-airport landings. Metallurgical examination of the fractured landing gear leg by the National Transportation Safety Board’s Materials Laboratory found that the gear leg, which was composed of hardened alloy steel, had fractured through the cross-section, perpendicular to the longitudinal direction. River patterns on the fracture surface emanated from an area consistent with the start of the fracture sequence. A closer view of the area revealed several thumbnail-shaped cracks with a large, vertically orientated ratchet mark on the fracture surface. The cracks exhibited crack arrest marks, consistent with crack propagation, and ratchet marks, consistent with multiple crack initiation sites. The end of the largest thumbnail crack on the fracture surface exhibited fatigue striations, consistent with fatigue crack propagation. The rest of the fracture surface exhibited dimpled rupture, consistent with overstress fracture. The crack initiation sites contained iron oxides with elements typical of salt and marine environments. The fatigue crack initiation site near the larger ratchet mark contained a corrosion pit. These features indicated that the gear leg fractured due to the stress concentration of fatigue cracks that had propagated inward from the lower surface of theleg. The fatigue cracks initiated from corrosion pits in an area of the leg without paint and primer. ## Aircraft - Registration: [N592KB](https://openairdocs.org/aircraft/N592KB), registered now, S/N U20601770, built 1972 (OpenAirDocs) - Reported make and model: CESSNA U206F - Registry model: [Cessna U206F](https://openairdocs.org/model/cessna-u206f) (registry code 2073333) (OpenAirDocs) - Registry engine: [Continental IO-520 series](https://openairdocs.org/engine/continental-io-520-series) (registry code 17032, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: U20601770 - Year built: 1972 - Airframe hours: 5034.3 - Engines: CONT MOTOR IO-520-F 285 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial observation, Part 135 - Operator: K Bay Air LLC - Registered owner: Ak Air Leasing LLC - Airworthiness certificate: Standard, Normal - Last inspection: Annual, November 12, 2021 - Departed: PAHO, Homer, AK - Destination: Same as departure - Flight plan: Company VFR - Equipment: Stall warning system, ADS-B, Handheld GPS, Satellite tracking device ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 43; injuries: none; flight instructor, commercial; airplane ratings: single-engine sea, single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; last flight review May 12, 2022; seat: left; restraint: 3-point; flight hours: 6,500 total, 2,000 in this make and model, 6,410 as pilot in command, 56 in the last 90 days, 56 in the last 30 days, 1.3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 59 °F, dew point 43 °F - Altimeter: 29.79 inHg - Observed at: PADQ, 66 nm away - METAR: PADQ 081905Z 30008KT 10SM SCT026 15/06 A2979 RMK AO2 T01500061 ## 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 20220608005049A](https://openairdocs.org/incident/20220608005049A), Jun 8, 2022: Cessna 206, Kodiak, AK, Substantial damage. Aircraft departed homer, AK @ approximately 1000 hrs, 1 pilot and 4 passengers on board, following 3 other company aircraft for flight seeing/bear viewing. The… ## Docket (7 files) The files NTSB released with the investigation on August 23, 2023, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=105232. 12.0 MB in all. - Materials laboratory factual report (item 1, PDF, 16 pages, 21 photos, 5.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14678727&FileExtension=pdf&FileName=22-081%20-%20Materials%20Lab%20Factual%20Report%20(ANC22LA040)-Rel.pdf - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 2, PDF, 11 pages, 3.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14781758&FileExtension=pdf&FileName=NTSB%20report%202KB_Redacted-Rel.pdf - Pilot statement (item 3, PDF, 1 page, 45 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14780970&FileExtension=pdf&FileName=Joe%27s%20statement-Rel.pdf - Director of maintenance statement (item 4, PDF, 1 page, 468 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14783670&FileExtension=pdf&FileName=Maintenance%20History_Redacted-Rel.pdf - Excerpt of maintenance records (item 5, PDF, 1 page, 760 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14781679&FileExtension=pdf&FileName=Last%20Annual_Redacted-Rel.pdf - Excerpt of gear leg form 337 (item 6, PDF, 1 page, 486 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14781202&FileExtension=pdf&FileName=gear%20leg%20337-Rel.pdf - Accident photographs (item 7, PDF, 2 pages, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14781516&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.