# NTSB ANC23LA070: Oliver Robert K Oliver Series 6, N151RF, Big Delta, AK, August 25, 2023 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Class 3 · Limited · Final report - Date: August 24, 2023, 16:00 local (Aug 25, 2023, 00:00 UTC) - Place: Big Delta, AK - Coordinates: 64.102592, -145.78693 - Nearby events: https://openairdocs.org/map.md?lat=64.1026&lon=-145.7869&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute: Unknown or undetermined](https://openairdocs.org/ntsb-events/000) - Highest injury: Minor injuries - Injuries: 2 minor - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Alaska Regional Office - Parties: FAA - NTSB case key (mKey): 192993 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC23LA070 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/192993/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=192993 - Page: https://openairdocs.org/ntsb/ANC23LA070 ## Probable cause A partial loss of engine power for undetermined reasons. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine (reciprocating)](https://openairdocs.org/ntsb-findings/01058500): Aircraft › Aircraft power plant · Unknown/Not determined (probable cause); cases with it: [Oliver Robert K OLIVER SERIES 6, 1 case](https://openairdocs.org/ntsb-findings/01058500/cases.md?model=05610MX), [All aircraft, 497 cases](https://openairdocs.org/ntsb-findings/01058500/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute: Unknown or undetermined](https://openairdocs.org/ntsb-events/000) (defining event); cases with it: [Oliver Robert K OLIVER SERIES 6, 1 case](https://openairdocs.org/ntsb-events/000/sequence.md?model=05610MX), [All aircraft, 1,703 cases](https://openairdocs.org/ntsb-events/000/sequence.md) - [Landing: Nose over/nose down](https://openairdocs.org/ntsb-events/096); cases with it: [Oliver Robert K OLIVER SERIES 6, 1 case](https://openairdocs.org/ntsb-events/096/sequence.md?model=05610MX), [All aircraft, 2,287 cases](https://openairdocs.org/ntsb-events/096/sequence.md) ## Analysis The pilot reported that he was about 10 to 15 minutes from his destination when the airplane sustained a partial loss of engine power. He pulled the carburetor heat on but power was not restored. He moved the throttle control from idle to full power and the engine would only increase to about 25% with full throttle. The pilot decided to make a forced landing along a treeless mountain ridgeline. During landing, a strong gust of wind lifted the airplane’s right wing and subsequently the left wing and engine impacted terrain and the airplane nosed over. The airplane sustained substantial damage to the fuselage and wings. After the accident, control continuity was established between the cockpit and engine. Although both carburetor bowls were empty of fuel, when disconnected the fuel line had fuel drain from both sides of the disconnection, consistent with fuel being fed to the engine at the time of operation. Thumb compression was established for all four cylinders. The top spark plugs all appeared to be normal; the lower spark plugs in the two right cylinders had oil in them, as did the forward right cylinder, which contained about a cup of oil. Small amounts of water were drained from the two left cylinders. The wreckage was stored unprotected outside on a trailer buried in snow and the engine was laying on it side which would account for the oil and water found in the engine. Postaccident examination of the engine revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation. Although weather conditions were conducive to serious carburetor icing at glide power, the pilot reported application of carburetor heat after the power loss with no effect. Accordingly, the reason for the power loss could not be determined. ## Factual narrative On August 24, 2023, about 1600 Alaska daylight time, a Kitfox Series 6 experimental airplane, N151RF, sustained substantial damage when it was involved in an accident near Delta Junction, Alaska. The pilot and passenger sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that he was flying around the Salcha River area and decided to fly to Charley River. About 10 to 15 minutes from his destination, the engine sustained a partial loss of power. To troubleshoot the loss of power, he pulled carburetor heat on but power was not restored. He moved the throttle control from idle to full power and the engine would only increase to about 25% with full throttle. The pilot decided to make a forced landing along a treeless mountain ridgeline. During landing, a strong gust of wind lifted the airplane’s right wing and subsequently the left wing and engine impacted terrain and the airplane nosed over. The airplane sustained substantial damage to the fuselage and wings. The postaccident examination of the engine revealed no evidence of any preimpact mechanical malfunctions or anomalies that would have precluded normal operation. Control continuity was established between the cockpit and engine. Although both carburetor bowls were empty of fuel, when disconnected the fuel line had fuel drain from both sides of the disconnection. Thumb compression was established for all four cylinders. The top spark plugs all appeared to be normal; the lower spark plugs in the two right cylinders had oil in them, as did the forward right cylinder, which contained about a cup of oil. Small amounts of water were drained from the two left cylinders. ## Aircraft - Registration: [N151RF](https://openairdocs.org/aircraft/N151RF), registered now, S/N S69912-006, built 2000 (OpenAirDocs) - Reported make and model: OLIVER ROBERT K OLIVER SERIES 6 - Registry model: [Oliver Robert K OLIVER SERIES 6](https://openairdocs.org/model/oliver-robert-k-oliver-series-6) (registry code 05610MX) (OpenAirDocs) - Registry engine: [Bombardier ROTAX (ALL)](https://openairdocs.org/engine/bombardier-rotax-all) (registry code 09050, reciprocating) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: S69912-006 - Year built: 2000 - Airframe hours: 1460 - Engines: BOMBARDIER ROTAX (ALL) 100 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Condition, May 1, 2023 - Departed: D66, Delta Junction, AK - Equipment: None ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 40; injuries: minor; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review April 1, 2023; seat: left; restraint: 4-point; flight hours: 3,865 total, 100 in this make and model, 1,837 as pilot in command, 270 in the last 90 days, 73 in the last 30 days, 0 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 280° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: 7,500 ft broken - Temperature: 64 °F, dew point 54 °F - Altimeter: 29.77 inHg - Observed at: PAFA ## 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 20230825016369A](https://openairdocs.org/incident/20230825016369A), Aug 25, 2023: Oliver Robert K OLIVER SERIES 6, Fairbanks, AK, Substantial damage. Aircraft departed delta junction with the [privacy data omitted]pilot and one pax. Aircraft continued flight to the hills north of Fairbanks and developed a… ## Docket (7 files) The files NTSB released with the investigation on July 24, 2024, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=192993. 11.7 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 5.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16756523&FileExtension=pdf&FileName=ANC23LA070%206120_Redacted-Rel.pdf - Carb ice chart (item 2, PDF, 1 page, 281 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17012667&FileExtension=pdf&FileName=ANC24LA070%20Carb%20ice%20chart-Rel.pdf - Engine examination (item 3, PDF, 11 pages, 868 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17409655&FileExtension=pdf&FileName=ANC23LA070%20Engine%20exam_Redacted-Rel.pdf - Mor delay in wreckage examination (item 4, PDF, 1 page, 63 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17013155&FileExtension=pdf&FileName=ANC23LA070%20MOR%20delay%20in%20wreckage%20exam-Rel.pdf - Maintenance records (item 5, PDF, 2 pages, 2.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16756815&FileExtension=pdf&FileName=ANC23LA070%20Maintenance%20logbooks_Redacted-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 6, PDF, 1 page, 16 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16755859&FileExtension=pdf&FileName=ANC23LA070%20Wreckage%20Release%20Form%20N151RF_Redacted-Rel.pdf - Investigative photographs (item 7, PDF, 3 pages, 2.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16756284&FileExtension=pdf&FileName=ANC23LA070%20Investigative%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.