# NTSB WPR18LA043: Beech A36, N251E, Rio Oso, CA, December 4, 2017 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Class 3 · Limited · Final report - Date: December 4, 2017, 07:20 local (15:20 UTC) - Place: Rio Oso, CA · Open field - Coordinates: 38.94947, -121.49016 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=38.9495&lon=-121.4902&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Fire/smoke (non-impact)](https://openairdocs.org/ntsb-events/150) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 96424 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR18LA043 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/96424/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=96424 - Page: https://openairdocs.org/ntsb/WPR18LA043 ## Probable cause An in-flight fire due to electrical arc corrosion of the fuel line. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Electrical power system: electrical pwr sys wiring](https://openairdocs.org/ntsb-findings/01022497): Aircraft › Aircraft systems · Damaged/degraded (probable cause); cases with it: [Beech A36, 1 case](https://openairdocs.org/ntsb-findings/01022497/cases.md?model=1151604), [All aircraft, 44 cases](https://openairdocs.org/ntsb-findings/01022497/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Fire/smoke (non-impact)](https://openairdocs.org/ntsb-events/150) (defining event); cases with it: [Beech A36, 3 cases](https://openairdocs.org/ntsb-events/150/sequence.md?model=1151604), [All aircraft, 504 cases](https://openairdocs.org/ntsb-events/150/sequence.md) - [Enroute-cruise: Fire/smoke (non-impact)](https://openairdocs.org/ntsb-events/150); cases with it: [Beech A36, 3 cases](https://openairdocs.org/ntsb-events/150/sequence.md?model=1151604), [All aircraft, 504 cases](https://openairdocs.org/ntsb-events/150/sequence.md) - [Enroute-descent: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Beech A36, 78 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=1151604), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The pilot reported that, during cruise flight, he saw flickering from below his seat and that he observed a fire had started when he looked under his seat. He made an emergency landing to an open field and exited the airplane before it burst into flames. The cockpit was thermally damaged, and the airplane sustained substantial damaged to the undercarriage of the fuselage. Examination of the fuel selector valve trim panel with attached wires, a fuel flow valve with fuel lines, and a portion of electrical wiring revealed a pin hole in a fuel line near the fuel selector valve as well as damaged electrical wiring. Damage to the fuel line was consistent with electrical arc corrosion. ## Factual narrative On December 4, 2017, about 0720 Pacific standard time, a Beechcraft A36, N251E, was substantially damaged when it was involved in an accident near Rio Oso, California. The pilot received minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the pilot, he was flying from McClellan Airfield (MCC), Sacramento, California, to Yuba County Airport (MYV), Marysville, California. The preflight, engine start, taxi and takeoff were normal from MCC. While in cruise flight, the pilot noticed a “flicker” below his seat. When he checked under the seat, he observed that a fire had started. He then identified a field to make an emergency landing. The pilot stated that he landed gear up in a plowed field, where the airplane came to rest upright facing about 150° from its original direction of travel. After the pilot exited the airplane, it burst into flames; the airplane cockpit was thermally damaged. An examination of the airframe near the left side of the airplane revealed burnt electrical wires and a hole in a fuel line near the area of the fuel valve inside the cockpit. The fuel selector valve trim panel with attached wires, a fuel flow valve with fuel lines, and a portion of electrical wiring were submitted to the National Transportation Safety Board Materials Laboratory in Washington, DC, for further examination. Examination found that the trim panel for the fuel selector valve had melted and missing insulation, which were consistent with exposure to a fire environment. The attached wiring did not exhibit electrical arcing. The fuel selector valve had sooting present on some of the fuel lines and a rough spot and pin hole near a 90º bend were observed. The rough spot exhibited cratering and re-solidified metal splatter that adhered to the fuel line surface and the hole through the fuel line wall. Both features are consistent with electrical arc erosion of the fuel line. The trim panel and fuel selector valve were positioned as they would have been installed in the accident airplane. The damaged portion of the fuel line aligned with the damage on the trim panel. A portion of electrical wiring was examined, and the terminal connector exhibited electrical arc corrosion. ## Aircraft - Registration: [N251E](https://openairdocs.org/deregistered/N251E-2019-11-29), registration cancelled 2019-11-29, S/N E-1962, built 1981 (OpenAirDocs) - Reported make and model: BEECH A36 (UNDESIGNAT) - Registry model: [Beech A36](https://openairdocs.org/model/beech-a36) (registry code 1151604) (OpenAirDocs) - Registry engine: [Continental IO-520 series](https://openairdocs.org/engine/continental-io-520-series) (registry code 17032, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: E-1962 - Year built: 1981 - Airframe hours: 4917.7 - Engines: Continental IO-550-B 285 horsepower reciprocating - Damage: Substantial damage - Fire: In-Flight - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, May 25, 2017 - Departed: MCC, SACRAMENTO, CA - Destination: MYV, MARYSVILLE, CA - Airport: MYV, Yuba County - Equipment: Stall warning system, Onboard weather, Handheld GPS, Auto-pilot ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 60; injuries: none; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, with waivers/limitations; last flight review June 22, 2017; seat: left; restraint: 3-point; flight hours: 6,023 total, 261 in this make and model, 6,108 as pilot in command, 78 in the last 90 days, 38 in the last 30 days, 0 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 350° at 15 knots, gusting 21 - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 6 °F, dew point -1 °F - Altimeter: 30.20 inHg - Observed at: MCC, 15 nm away ## 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 20171204023509A](https://openairdocs.org/incident/20171204023509A), Dec 4, 2017: Beech A36, Rio Oso, CA, Substantial damage. Aircraft departed mclellan airport (mcc) en-route to marysville (mrv). Preflight, engine start, taxi/takeoff were normal. Enroute to marysville, pilot reported… ## Docket (7 files) The files NTSB released with the investigation on December 21, 2021, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=96424. 30.5 MB in all. - Materials laboratory factual report (item 1, PDF, 5 pages, 549 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12980642&FileExtension=pdf&FileName=Materials%20Laboratory%20Report%2018-098-Rel.pdf - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 2, PDF, 9 pages, 3.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12980443&FileExtension=pdf&FileName=6120_Redacted-Rel.pdf - FAA inspector's statement (item 3, PDF, 1 page, 45 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12979075&FileExtension=pdf&FileName=FAA%20Statement-Rel.pdf - Excerpt maintenance logs (item 4, PDF, 27 pages, 18.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13044030&FileExtension=pdf&FileName=Excerpt%20MX%20Logs%20(1)_Redacted-Rel.pdf - Evidence control form (item 5, PDF, 3 pages, 905 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13044147&FileExtension=pdf&FileName=WPR18LA043%20Chain%20of%20Custody_Redacted-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 6, PDF, 2 pages, 231 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12980453&FileExtension=pdf&FileName=wreckage%20release_Redacted-Rel.pdf - FAA photos (item 7, PDF, 4 pages, 7.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12979190&FileExtension=pdf&FileName=FAA%20photos%20fire%20damaged%20line-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.