# NTSB ERA23LA361: Beech V35, N5431U, Rutledge, TN, September 2, 2023 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: September 2, 2023, 11:00 local (15:00 UTC) - Place: Rutledge, TN · Wooded area. - Coordinates: 36.304388, -83.4433 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=36.3044&lon=-83.4433&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Eastern Region Aviation - Parties: FAA/FSDO - NTSB case key (mKey): 193000 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA23LA361 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/193000/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=193000 - Page: https://openairdocs.org/ntsb/ERA23LA361 ## Probable cause A total loss of engine power due to the fatigue failure of a retaining circlip in one of the No. 2 crankshaft cheek counterweights, which resulted in liberation of the counterweight. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine (reciprocating): recip engine power section](https://openairdocs.org/ntsb-findings/01058520): Aircraft › Aircraft power plant · Fatigue/wear/corrosion (probable cause); cases with it: [Beech V35, 2 cases](https://openairdocs.org/ntsb-findings/01058520/cases.md?model=1151538), [All aircraft, 233 cases](https://openairdocs.org/ntsb-findings/01058520/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Beech V35, 10 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=1151538), [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: [Beech V35, 9 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=1151538), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) ## Analysis The pilot reported that he was about 15 minutes into the cross-country flight when the engine made a “loud bang,” began to run rough, and eventually seized. Unable to glide to an open field, the pilot conducted a forced landing into trees. He and his passenger were not injured; however, the airplane was substantially damaged. Examination revealed several holes in the engine case, and one of the No. 2 crankshaft cheek counterweights was missing. Further examination revealed two of the counterweight retaining circlips were fractured. Examination of the fractured circlips revealed that one of the circlip legs failed from fatigue crack propagation. The engine had been disassembled and the crankshaft inspected due to a propeller strike about 130 operating hours before the accident. ## Factual narrative On September 2, 2023, about 1100 eastern daylight time, a Beech V35 airplane, N5431U, was substantially damaged when it was involved in an accident near Rutledge, Tennessee. The airline transport pilot and one passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that the flight departed Gatlinburg/Pigeon Forge Airport (GKT), Sevierville, Tennessee, about 1045. The pilot proceeded northbound toward his destination, climbing to 2,500 ft mean sea level. About 15 minutes into the flight, over a forested area, the engine made a “loud bang” and started running rough. As the pilot turned to a southerly heading and an open field, the engine seized. Unable to land in the field, he performed a forced landing into trees. The wreckage came to rest inverted, and the pilot and passenger were met by first responders. Federal Aviation Administration inspectors responded to the accident site and examined the wreckage. There was no fire. The fuselage, wings, and empennage were substantially damaged. The external surfaces of the fuselage were covered with engine oil. After recovery of the wreckage, the engine was removed from the airframe for examination. Several small (about 0.75 inch) holes were found in the upper engine case, and one large hole was found under the area of the left magneto. The oil pan was removed and it contained engine oil and numerous metallic fragments. Further disassembly of the engine revealed that one of the No. 2 crankshaft cheek counterweights was missing. The largest hole in the engine case was directly adjacent to the area where the counterweight liberated. The retaining circlips and plates from the counterweight were found inside the engine. Two of the circlips were fractured, and two were bent but intact. The plates and circlips were forwarded to the NTSB Materials Laboratory for analysis. The circlips were arbitrarily numbered 1 though 4. Circlips 1 and 2 were intact and bent. Circlip 3 was fractured at both leg ends. An examination of both fracture surfaces revealed localized necking and cup-shaped fracture surfaces consistent with overstress. Circlip 4 also had both leg ends fractured. One of the fractures was similar to the circlip 3 fractures; however, the other fracture exhibited two thumbnail-shaped cracks along the inner surface. There were also fatigue striations consistent with fatigue crack propagation. A review of the aircraft maintenance records revealed that the engine was disassembled and inspected for a propeller strike on November 2, 2020, at 5,061 total airframe hours. The airplane had accrued about 130 hours since this inspection. ## Aircraft - Registration: [N5431U](https://openairdocs.org/aircraft/N5431U), registered now, S/N D-8515, built 1967 (OpenAirDocs) - Reported make and model: BEECH V35 - Registry model: [Beech V35](https://openairdocs.org/model/beech-v35) (registry code 1151538) (OpenAirDocs) - Registry engine: [Continental IO-520 series](https://openairdocs.org/engine/continental-io-520-series) (registry code 17032, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: D-8515 - Year built: 1967 - Airframe hours: 5191 - Engines: Continental IO-520-BA 285 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, August 15, 2023 - Departed: GKT, Sevierville, TN - Destination: I35, Harlan, KY - Equipment: Satellite tracking device, Onboard weather, Electronic primary flight display, Electronic multifunction display, Auto-pilot, ADS-B, Stall warning system ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 73; injuries: none; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: basicmed, without waivers/limitations; last flight review April 18, 2023; seat: left; restraint: 4-point; flight hours: 15,000 total, 500 in this make and model, 25 in the last 90 days, 10 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 77 °F, dew point 64 °F - Altimeter: 30.27 inHg - Observed at: KDKX, 29 nm away - METAR: KDKX 021455Z AUTO 00000KT 10SM CLR 25/18 A3027 RMK A01 ## 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 20230902013979A](https://openairdocs.org/incident/20230902013979A), Sep 2, 2023: Beech V35, Rutledge, TN, Destroyed. Accident occurred on 9/2/2023 after aircraft engine seized inflight. Pilot stated he felt a brief vibration and engine shudder prior to engine seizing. Pilot… ## Docket (6 files) The files NTSB released with the investigation on December 5, 2024, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=193000. 25.5 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 4.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16597058&FileExtension=pdf&FileName=1%206120_Redacted-Rel.pdf - NTSB record of conversation/interview (item 2, PDF, 5 pages, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16596837&FileExtension=pdf&FileName=2%20FINAL%20Record%20of%20Convo%20w%20David%20Brown%209%202%202023%20v02_Redacted-Rel.pdf - Excerpts - aircraft logbook (item 3, PDF, 20 pages, 10.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16690851&FileExtension=pdf&FileName=3%20Excerpts%20-%20Aircraft%20Logbook_Redacted-Rel.pdf - Excerpts - engine logbook (item 4, PDF, 6 pages, 3.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16597990&FileExtension=pdf&FileName=4%20Excerpts%20-%20Engine%20Logbook_Redacted-Rel.pdf - NTSB examination summary (item 5, PDF, 6 pages, 375 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17567069&FileExtension=pdf&FileName=6%20NTSB%20Examination%20Summary-Rel.pdf - Materials laboratory factual report (item 6, PDF, 17 pages, 22 photos, 5.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17565997&FileExtension=pdf&FileName=24-043%20-%20Materials%20Lab%20Factual%20Report%20(ERA23LA361)-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.