# NTSB WPR19LA273: Smyth Sidewinder, N492AC, Tucumcari, NM, September 14, 2019 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: September 14, 2019, 11:25 local (17:25 UTC) - Place: Tucumcari, NM - Coordinates: 35.125556, -103.83916 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=35.1256&lon=-103.8392&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 100401 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR19LA273 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/100401/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=100401 - Page: https://openairdocs.org/ntsb/WPR19LA273 ## Probable cause The in-flight separation of a section of a propeller blade due to a fatigue crack, which resulted in a forced landing. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Propeller system: propeller blade section](https://openairdocs.org/ntsb-findings/01046111): Aircraft › Aircraft propeller/rotor · Fatigue/wear/corrosion (probable cause); cases with it: [Crimmins Arthur SIDEWINDER, 1 case](https://openairdocs.org/ntsb-findings/01046111/cases.md?model=0561197), [All aircraft, 51 cases](https://openairdocs.org/ntsb-findings/01046111/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338) (defining event); cases with it: [Crimmins Arthur SIDEWINDER, 1 case](https://openairdocs.org/ntsb-events/338/sequence.md?model=0561197), [All aircraft, 563 cases](https://openairdocs.org/ntsb-events/338/sequence.md) - [Landing: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Crimmins Arthur SIDEWINDER, 1 case](https://openairdocs.org/ntsb-events/440/sequence.md?model=0561197), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) ## Analysis The pilot reported that during cruise flight, the engine momentarily started to run rough before he heard a loud bang followed by a separation of a portion of the propeller blade. The pilot shut the engine down and performed a forced landing to open desert terrain, during which the airplane impacted vegetation, resulting in substantial damage to the left wing. Postaccident examination of the propeller blade revealed a chordwise fracture across the propeller about 12 inches from the hub. The fracture origin area exhibited a small pit, consistent with progressive crack growth from a flat fracture surface in the area identified as the origin. The pit was likely initiated by corrosion, as it exhibited evidence of chlorine-containing salts. No maintenance logbooks were located for the propeller, and its total time in service and most recent inspection were not determined. ## Factual narrative On September 14, 2019, about 1125 mountain daylight time, an experimental, amateur-built Sidewinder airplane, N492AC, was substantially damaged when it was involved in an accident near Tucumcari, New Mexico. The commercial pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that, during cruise flight at 11,500 ft mean sea level (msl), the engine momentarily started to run rough. He then heard a loud bang, followed by a portion of propeller blade separating from the fixed-pitch propeller assembly. The pilot shut the engine down by moving the mixture handle to the idle cut-off position and turning off the magneto switch; the engine continued to windmill during the descent and was “still very wobbly.” The pilot performed a forced landing to open desert terrain, during which the airplane impacted vegetation, resulting in substantial damage to the left wing. Review of photos of the airplane revealed that one of the propeller blades was separated about 12 inches from the hub. Examination of the propeller fracture surface revealed that the fracture origin area exhibited a small pit. Further examination with a scanning electron microscope revealed fracture features consistent with progressive crack growth from a flat fracture surface in the area that was identified as the origin. The fracture features were consistent with a fatigue fracture originating from the pit. Energy dispersive spectroscopy of the origin area revealed chlorine-containing salts, which were consistent with a corrosion-initiated pit. No propeller logbooks were located during the investigation. It could not be determined when the propeller was last inspected or overhauled, or its total time in service. ## Aircraft - Registration: [N492AC](https://openairdocs.org/aircraft/N492AC), registered now, S/N 002 (OpenAirDocs) - Reported make and model: Smyth SIDEWINDER (No Series) - Registry model: [Crimmins Arthur SIDEWINDER](https://openairdocs.org/model/crimmins-arthur-sidewinder) (registry code 0561197) (OpenAirDocs) - Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: 002 - Year built: 2003 - Airframe hours: 60 - Engines: Lycoming O-320-E2A 150 hp reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Condition, September 1, 2019, 11.4 hours before - Departed: Gallup, NM - Destination: KTUS, Altus, NM ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 27; injuries: none; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; last flight review April 6, 2019; seat: left; restraint: 3-point; flight hours: 451.1 total, 12.2 in this make and model, 388.4 as pilot in command, 101.1 in the last 90 days, 56.7 in the last 30 days, 8 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 210° at 16 knots, gusting 22 - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 84 °F, dew point 59 °F - Altimeter: 30.22 inHg - Observed at: KTCC, 12 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 20190914013139A](https://openairdocs.org/incident/20190914013139A), Sep 14, 2019: Crimmins Arthur SIDEWINDER, Tucumcari, NM, Substantial damage. On September 14, 2019 at 1125 MDT, a 2003 Sidewinder experimental amateur built aircraft, N492AC, [privacy data omitted], experienced a propeller blade failure… ## Docket (3 files) The files NTSB released with the investigation on March 1, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=100401. 7.3 MB in all. - Materials laboratory factual report (item 1, PDF, 6 pages, 6 photos, 1.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11663854&FileExtension=pdf&FileName=Materials%20Laboratory%20Factual%20Report%2020-054-Rel.pdf - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 2, PDF, 11 pages, 5.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11663810&FileExtension=pdf&FileName=6120_Redacted-Rel.pdf - Photo array (item 3, PDF, 2 pages, 2 photos, 390 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11663622&FileExtension=pdf&FileName=Photo%201-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.