# NTSB CEN23LA370: Piper PA31, N3589X, Durant, OK, August 21, 2023 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: August 21, 2023, 10:48 local (15:48 UTC) - Place: Durant, OK - Coordinates: 33.939698, -96.395057 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=33.9397&lon=-96.3951&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: FAA FSDO - NTSB case key (mKey): 192908 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN23LA370 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/192908/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=192908 - Page: https://openairdocs.org/ntsb/CEN23LA370 ## Probable cause The loosening of a connecting rod cap nut for reasons that could not be determined, which resulted in a mechanical failure of the engine and an in-flight fire. ## 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: [Piper PA-31-350, 1 case](https://openairdocs.org/ntsb-findings/01058530/cases.md?model=7103110), [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: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) (defining event); cases with it: [Piper PA-31-350, 3 cases](https://openairdocs.org/ntsb-events/340/sequence.md?model=7103110), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) - [Enroute: Fire/smoke (non-impact)](https://openairdocs.org/ntsb-events/150); cases with it: [Piper PA-31-350, 3 cases](https://openairdocs.org/ntsb-events/150/sequence.md?model=7103110), [All aircraft, 504 cases](https://openairdocs.org/ntsb-events/150/sequence.md) - [Landing: Fire/smoke (non-impact)](https://openairdocs.org/ntsb-events/150); cases with it: [Piper PA-31-350, 3 cases](https://openairdocs.org/ntsb-events/150/sequence.md?model=7103110), [All aircraft, 504 cases](https://openairdocs.org/ntsb-events/150/sequence.md) ## Analysis While in flight, the pilot heard and felt a bang from the right side of the airplane. He saw that the right engine nacelle had a hole in it and the engine was on fire. He secured the engine and diverted to a nearby airport. While on final approach for landing, the engine fire reignited. The pilot landed the airplane, taxied clear of the runway, shut down the left engine, and egressed. The engine fire continued to burn and consumed the right engine and a majority of the fuselage. Examination revealed that the right engine’s No. 2 cylinder was displaced from the engine case but remained attached via the injector manifold vent tube and injector lines. All eight of the No. 2 cylinder’s attach bolts were broken off at the case. The connecting rod cap was found lodged in the bottom of the piston. One connecting rod bolt was found broken off flush in the connecting rod; the top portion was not located. The other connecting rod bolt remained in the connecting rod cap with the nut also not located. One side of the lower connecting rod flange was bent back towards the piston, capturing the nut and remaining portion of the broken bolt. Neither bearing half could be identified in the remaining material. Numerous impact marks were noted on the piston, cylinder, and case. A review of maintenance records found that the engine was last overhauled about 4 ½ years before the accident and had accrued about 900 hours since the overhaul. Based on the available information, it is likely that the nut that secured one side of the connecting rod cap became loose, resulting the separation of the cap and subsequent damage to the No. 2 cylinder. Since the nut could not be located, the reason it did not remain secure could not be determined. ## Factual narrative On August 21, 2023, about 1048 central daylight time, a Piper PA-31-350 airplane, N3589X, was substantially damaged when it was involved in an accident near Durant, Oklahoma. The pilot was not injured. The airplane was operated under Title 14 Code of Federal Regulations Part 91 as an aerial observation flight. The pilot reported that, while in flight, he heard and felt a bang from the right side of the airplane. He saw that the right engine nacelle had a hole in it and the engine was on fire. He then shut down and secured the engine, which appeared to stop the engine fire, and diverted to a nearby airport. While on final approach for landing, the engine fire reignited. The pilot landed the airplane, taxied clear of the runway, shut down the left engine, and egressed. The engine fire continued to burn and consumed the right engine and a majority of the fuselage. An engine examination revealed that the No. 2 cylinder was displaced from the engine case but remained attached via the injector manifold vent tube and injector lines. All eight of the No. 2 cylinder’s attach bolts were broken off at the case. The connecting rod cap was found lodged in the bottom of the piston. One connecting rod bolt was found broken off flush in the connecting rod; the top portion was not located. The other connecting rod bolt remained in the connecting rod cap with the nut also not located. One side of the lower connecting rod flange was bent back towards the piston, capturing the nut and remaining portion of the broken bolt. Neither bearing half was identified. Numerous impact marks were noted on the piston, cylinder, and case. A review of maintenance records found that the engine was last overhauled on March 20, 2019, and installed on the airplane on October 1, 2020. The airplane had accrued about 900 hours since the overhaul. ## Aircraft - Registration: [N3589X](https://openairdocs.org/aircraft/N3589X), registered now, S/N 31-8052138, built 1980 (OpenAirDocs) - Reported make and model: PIPER PA31 (350) - Registry model: [Piper PA-31-350](https://openairdocs.org/model/piper-pa-31-350) (registry code 7103110) (OpenAirDocs) - Registry engine: [Lycoming TI0-540 series](https://openairdocs.org/engine/lycoming-ti0-540-series) (registry code 41533, turbo-prop) (OpenAirDocs) - Category: Airplane - Serial number: 31-8052138 - Year built: 1980 - Airframe hours: 22698.4 - Engines: Lycoming TSIO-540 350 horsepower reciprocating; Lycoming TSIO-540 350 horsepower reciprocating - Damage: Substantial damage - Fire: Both - Flight: Aerial observation, Part 91 - Operator: Marc Inc - Registered owner: Marc Inc - Airworthiness certificate: Standard, Normal - Last inspection: Annual, August 11, 2022 - Departed: KRVS, Tulsa, OK - Destination: KDUA, Durant, OK - Airport: DUA, Durant Rgnl/Eaker Fld, runway 17, 6,800 × 100 ft, asphalt - Equipment: ADS-B ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 36; injuries: none; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review October 7, 2022; seat: left; flight hours: 3,300 total, 1,400 in this make and model, 3,189 as pilot in command, 130 in the last 90 days, 49 in the last 30 days, 9 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 100° at 7 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 93 °F, dew point 66 °F - Altimeter: 30.12 inHg - Observed at: KDUA - METAR: KDUA 211535Z AUTO 10007KT 10SM CLR 34/19 A3012 RMK AO2 ## 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 20230821012859A](https://openairdocs.org/incident/20230821012859A), Aug 21, 2023: Piper PA-31-350, Durant, OK, Destroyed. On August 21, 2023 at approximately 1057 CST, a Piper PA-31-350 aircraft was forced to make an emergency landing after the right engine experienced an inflight… ## Docket (5 files) The files NTSB released with the investigation on May 9, 2024, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=192908. 52.6 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 13 pages, 6.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16850034&FileExtension=pdf&FileName=cen23la370%20ntsb%20form%206120_Redacted-Rel.pdf - Photos (item 2, PDF, 6 pages, 5 photos, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16857752&FileExtension=pdf&FileName=Photos%205-Rel.pdf - Engine report summary (item 3, PDF, 4 pages, 3 photos, 610 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16850768&FileExtension=pdf&FileName=Lycoming%20Examination%20Summary-Rel.pdf - Overhaul entries (item 4, PDF, 2 pages, 38.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16850044&FileExtension=pdf&FileName=Overhaul%20entries_Redacted-Rel.pdf - Logbook entries (item 5, PDF, 4 pages, 4.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16852498&FileExtension=pdf&FileName=Log%20Scans_Redacted-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.