# NTSB ANC23LA051: Stinson 108, N97719, Ninilchik, AK, July 13, 2023 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: July 12, 2023, 16:24 local (Jul 13, 2023, 00:24 UTC) - Place: Ninilchik, AK · road - Coordinates: 60.033611, -151.65077 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=60.0336&lon=-151.6508&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - 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/FSDO - NTSB case key (mKey): 192643 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC23LA051 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/192643/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=192643 - Page: https://openairdocs.org/ntsb/ANC23LA051 ## Probable cause A partial loss of engine power due to failure of the No. 1 cylinder intake valve head. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine (reciprocating): recip eng cyl section](https://openairdocs.org/ntsb-findings/01058530): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Stinson 108, 1 case](https://openairdocs.org/ntsb-findings/01058530/cases.md?model=9230402), [All aircraft, 373 cases](https://openairdocs.org/ntsb-findings/01058530/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Stinson 108, 4 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=9230402), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Stinson 108, 2 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=9230402), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) - [Landing-landing roll: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Stinson 108, 6 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=9230402), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The pilot reported that while en route he noticed a loss of engine power and the oil pressure decreasing. He performed a forced landing to a road. During the landing rollout the right wingtip struck a sign, which resulted in substantial damage. Postaccident examination of the engine revealed the No. 1 cylinder was fractured from the engine and remained partially attached by exhaust tubes and the intake manifold. The intake valve stem was fractured about an inch from the interior base of the valve. The piston and intake valve were destroyed by the internal forces in the engine and the fragments were not located. ## Factual narrative On July 12, 2023, about 1624 Alaska daylight time, a Stinson 108 airplane, N97719, was substantially damaged when it was involved in an accident near Ninilchik, Alaska. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot stated he departed Homer Airport (HOM) destined for Anchorage, Alaska. A few miles northwest of the Ninilchik Airport (NIN) he noticed a loss of engine power and the oil pressure decreasing. The pilot determined he was too far from the NIN airport to return so he elected to perform a forced landing to a road. During the landing roll the right wingtip struck a traffic sign, which resulted in substantial damage to the right wing. Postaccident examination of the engine revealed the No. 1 cylinder was fractured from the engine and remained partially attached by exhaust tubes and the intake manifold. The intake valve head and stem was fractured about an inch from the interior base of the valve. The piston and intake valve were destroyed by the internal forces in the engine and the fragments were not located. The pilot reported the engine had a total time of 626 hours at the time of the accident. The last annual inspection was completed 12 months before the accident at an engine total time of 556.4 hours. The engine logbook showed the manufacturer’s recommended time between overhaul is 1,200 hours. ## Aircraft - Registration: [N97719](https://openairdocs.org/aircraft/N97719), registered now, S/N 108-719, built 1946 (OpenAirDocs) - Reported make and model: STINSON 108 - Registry model: [Stinson 108](https://openairdocs.org/model/stinson-108) (registry code 9230402) (OpenAirDocs) - Registry engine: [Franklin 6A4150 series](https://openairdocs.org/engine/franklin-6a4150-series) (registry code 27024, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 108-719 - Year built: 1946 - Airframe hours: 3211 - Engines: Franklin O335-150-B4 155 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, July 30, 2022 - Departed: PAHO, Homer, AK - Destination: PAEN, Kenai, AK - Airport: NIN, Ninilchik - Equipment: Electronic flight bag or handheld device, Handheld GPS ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 38; injuries: none; private; airplane ratings: single-engine land; medical: class 3, without waivers/limitations; last flight review September 25, 2022; seat: left; restraint: 4-point; flight hours: 204 total, 130 in this make and model, 149 as pilot in command, 24 in the last 90 days, 10 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 180° at 3 knots - Visibility: 10 statute miles - Lowest ceiling: 1,100 ft broken - Temperature: 55 °F, dew point 52 °F - Altimeter: 30.16 inHg - Observed at: AHO, 24 nm away - METAR: PAHO 121953Z 18003KT 10SM SCT007 BKN011 13/11 A3016 RMK AO2 SLP212 T01280106 ## 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 20230712014659A](https://openairdocs.org/incident/20230712014659A), Jul 12, 2023: Stinson 108, Ninilchik, AK, Substantial damage. From FAA form 8020-9 aircraft accident/incident preliminary notice, block/item 5.: emergency landing on a secondary dirt road and clipped wing on a road sign… ## Docket (5 files) The files NTSB released with the investigation on August 21, 2024, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=192643. 30.6 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 10.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16277824&FileExtension=pdf&FileName=NTSB%206120%20Form_Redacted-Rel.pdf - Engine examination (item 2, PDF, 9 pages, 1.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16277947&FileExtension=pdf&FileName=ANC23LA051%20Engine%20exam-Rel.pdf - Maintenance records (item 3, PDF, 9 pages, 17.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16820055&FileExtension=pdf&FileName=Maintenance%20Records_Redacted-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 4, PDF, 1 page, 121 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16891471&FileExtension=pdf&FileName=NTSB%20Release%20Signed_Redacted-Rel.pdf - Photos (item 5, PDF, 4 pages, 759 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16820836&FileExtension=pdf&FileName=Photos-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.