# NTSB ANC24LA045: Cessna 206, N756CL, King Salmon, AK, June 7, 2024 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: June 7, 2024, 15:05 local (23:05 UTC) - Place: King Salmon, AK - Coordinates: 58.677237, -156.65184 - Nearby events: https://openairdocs.org/map.md?lat=58.6772&lon=-156.6518&mi=10 - Phase of flight: [Emergency descent](https://openairdocs.org/ntsb-phases/600) (OpenAirDocs' grouping) - Defining event: [Emergency descent: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Alaska Regional Office - Parties: FAA, Continental Motors - NTSB case key (mKey): 194426 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC24LA045 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/194426/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=194426 - Page: https://openairdocs.org/ntsb/ANC24LA045 ## Probable cause A partial loss of engine power due to detonation/preignition of the No. 1 cylinder for reasons that could not be determined. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Power plant](https://openairdocs.org/ntsb-findings/01057100): Aircraft › Aircraft power plant · Malfunction (probable cause); cases with it: [Cessna U206G, 1 case](https://openairdocs.org/ntsb-findings/01057100/cases.md?model=2073356), [All aircraft, 198 cases](https://openairdocs.org/ntsb-findings/01057100/cases.md) - [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause); cases with it: [Cessna U206G, 4 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=2073356), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Emergency descent: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) (defining event); cases with it: [Cessna U206G, 1 case](https://openairdocs.org/ntsb-events/342/sequence.md?model=2073356), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md) ## Analysis The pilot reported that, shortly after takeoff, he observed high engine oil temperature and began to turn back to the airport. The engine began losing power, and the pilot performed a forced landing in the tundra, which resulted in substantial damage to the horizontal stabilizer and elevator. Examination of the engine revealed that the No. 1 piston was eroded down to the steel ring lands and scuff marks were observed on the side of the piston skirt. The No. 1 cylinder upper and lower spark plugs had molten aluminum deposits covering the electrodes and insulators. The crankshaft rod journals exhibited evidence of foreign material contamination in the oil. The Nos. 2 and 5 crankshaft rod journals had severe thermal discoloration. All connecting rod bearings exhibited abnormal wear. Connecting rod bearings No. 2 and 5 were severely damaged. The observed damage was consistent with a detonation/pre-ignition event; however, the reasons for the detonation/pre-ignition could not be determined based on the available information. ## Factual narrative On June 7, 2024, about 1505 Alaska daylight time, a Cessna 206 airplane, N756CL, sustained substantial damage when it was involved in an accident near King Salmon, Alaska. Both pilots onboard were uninjured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 flight. The pilot reported that, shortly after takeoff, he observed a high engine oil temperature indication and initiated a turn back to the airport. The engine began losing power and the pilot performed a forced landing to the tundra, which resulted in substantial damage to the horizontal stabilizer and elevator. The engine was rebuilt by Continental Motors in February 2018, and had accrued about 1,282 hours since the overhaul. A preliminary engine examination revealed that the oil filter media contained a considerable amount of metal. The engine was shipped to Continental Motors in Mobile, Alabama, for further examination, which revealed that the No. 1 piston was eroded down to the steel ring lands and scuff marks were observed on the side of the piston skirt. The upper and lower spark plugs in cylinder No. 1 had molten aluminum deposits covering the electrodes and insulators. The upper and lower spark plugs from cylinder No. 3 and the top spark plug from cylinder No. 4 displayed chipped porcelain insulators at the electrodes. All spark plugs were found worn beyond limits in accordance with the Champion Check-A-Plug chart. The crankshaft rod journals exhibited signs of foreign material contamination in the oil. Dark oil was observed in the sump case when it was drained. The No. 2 and No. 5 crankshaft rod journals had severe thermal discoloration. All connecting rod bearings exhibited abnormal wear. Connecting rod bearings Nos. 2 and 5 were severely damaged. All damage discovered was consistent with a pre-ignition/detonation event. The Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25B), states, in part: Detonation is an uncontrolled, explosive ignition of the fuel/air mixture within the cylinder's combustion chamber. It causes excessive temperatures and pressures which, if not corrected, can quickly lead to a failure of the piston, cylinder, or valves. In less severe cases, detonation causes engine overheating, roughness, or loss of power. Preignition occurs when the fuel/air mixture ignites prior to the engine's normal ignition event. Premature burning is usually caused by a residual hot spot in the combustion chamber, often created by a small carbon deposit on a spark plug, a cracked spark plug insulator, or other damage to the cylinder that causes a part to heat sufficiently to ignite the fuel/air charge. ## Aircraft - Registration: [N756CL](https://openairdocs.org/aircraft/N756CL), registered now, S/N U20603983, built 1977 (OpenAirDocs) - Reported make and model: CESSNA 206 - Registry model: [Cessna U206G](https://openairdocs.org/model/cessna-u206g) (registry code 2073356) (OpenAirDocs) - Registry engine: [Continental IO-520 series](https://openairdocs.org/engine/continental-io-520-series) (registry code 17032, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: U20603983 - Year built: 1977 - Airframe hours: 11598.8 - Engines: Continental IO550F17B 300 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Egli Air Haul Service - Registered owner: Sam Egli - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, November 2, 2023, 57.6 hours before - Departed: PAKN, King Salmon, AK - Destination: PAIG, Igiugig, AK - Flight plan: Company VFR - Equipment: Satellite tracking device, Electronic flight bag or handheld device, ADS-B, Stall warning system ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 47; injuries: none; airline transport, commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review March 30, 2024; seat: left; restraint: 4-point; flight hours: 162 total, 19 in this make and model, 1,498 as pilot in command, 18 in the last 90 days, 15 in the last 30 days - Other flight crew; age 72; injuries: none; commercial, military, flight instructor; airplane ratings: single-engine sea, multi-engine land, single-engine land; instrument ratings: airplane, helicopter; medical: class 1, with waivers/limitations; last flight review December 3, 2023; seat: right; restraint: 4-point; flight hours: 15,000 total, 2,000 in this make and model, 12,000 as pilot in command, 15 in the last 90 days ## Weather - Conditions: Visual (VMC), Day - Wind: 90° at 20 knots, gusting 32 - Visibility: 10 statute miles - Lowest ceiling: 6,500 ft broken - Temperature: 54 °F, dew point 34 °F - Altimeter: 29.98 inHg - Turbulence: Moderate - Observed at: PAKN, 3 nm away - METAR: PAKN 072354Z 09020G32KT 10SM BKN065 12/01 A2998 RMK AO2 PK WND 10032/2351 SLP150 T01170006 10122 20094 58009 ## 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 20240607008529A](https://openairdocs.org/incident/20240607008529A), Jun 7, 2024: Cessna U206G, King Salmon, AK, Substantial damage. On June 7, 2024 Cessna aircraft [privacy data omitted], a U206G, took off from the King Salmon Airport, akn on a part 91 flight under VFR. The aircraft made… ## Other investigations on N756CL (1) 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. - [NTSB ANC12CA027](https://openairdocs.org/ntsb/ANC12CA027), Mar 9, 2012: Cessna U206G (N756CL), Naknek, AK, substantial damage. Probable cause: The pilot's decision to take off from an unsuitable off-airport site. ## Docket (6 files) The files NTSB released with the investigation on April 23, 2025, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=194426. 11.0 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 9 pages, 1.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17277603&FileExtension=pdf&FileName=ANC24LA045%20Pilot%206120_Redacted-Rel.pdf - Engine examination (item 2, PDF, 13 pages, 2.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17887980&FileExtension=pdf&FileName=Field%20Notes%20engine%20exam-Rel.pdf - Maintenance records (item 3, PDF, 11 pages, 4.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17886217&FileExtension=pdf&FileName=N756CL%20IO550%20Eng%20SN%201035358%20Logbook_Redacted-Rel.pdf - Certification of party representative (Continental aerospace) (item 4, PDF, 9 pages, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17848685&FileExtension=pdf&FileName=Certification%20of%20Party%20Representative%20PG_Redacted-Rel.pdf - Party submission 1 (item 5, PDF, 9 pages, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17848595&FileExtension=pdf&FileName=Certification%20of%20Party%20Representative%20JF_Redacted-Rel.pdf - Photos (item 6, PDF, 4 pages, 407 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17849096&FileExtension=pdf&FileName=Investigative%20Photographs-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.