# NTSB CEN23FA410: Sonex Sonex, N569SX, Dowagiac, MI, September 10, 2023 - Type: NTSB accident investigation - Classification: Accident · Fatal · Class 3 · Field · Final report - Date: September 10, 2023, 12:00 local (16:00 UTC) - Place: Dowagiac, MI · WOODS - Coordinates: 42.04722, -86.09306 - Nearby events: https://openairdocs.org/map.md?lat=42.0472&lon=-86.0931&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: Fatal - Injuries: 1 fatal - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: FAA Flight Standards - NTSB case key (mKey): 193066 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN23FA410 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/193066/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=193066 - Page: https://openairdocs.org/ntsb/CEN23FA410 ## Probable cause The total loss of engine power due to the failure of the ignition distributor rotor. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Ignition system: magneto/distributor](https://openairdocs.org/ntsb-findings/01057414): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Martin Richard B SONEX, 1 case](https://openairdocs.org/ntsb-findings/01057414/cases.md?model=05619AM), [All aircraft, 101 cases](https://openairdocs.org/ntsb-findings/01057414/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: [Martin Richard B SONEX, 1 case](https://openairdocs.org/ntsb-events/341/sequence.md?model=05619AM), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Landing: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Martin Richard B SONEX, 1 case](https://openairdocs.org/ntsb-events/440/sequence.md?model=05619AM), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) - [Landing: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Martin Richard B SONEX, 1 case](https://openairdocs.org/ntsb-events/470/sequence.md?model=05619AM), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The pilot departed for a local flight and an alert notice (ALNOT) was issued when the pilot did not return. A search effort concluded four days later when the wreckage was found in a heavily wooded area about 4 miles from the departure airport. No ADS-B data associated with the airplane, or the accident flight was available. At the time of the on-scene examination, the transponder was observed in the OFF position. Impact signatures on the propeller were consistent with the propeller not rotating at impact. Examination of the engine revealed that the ignition distributor rotor was fractured and disconnected from its driveshaft. This resulted in a total loss of engine power when the ignition system became inoperative due to the rotor failure. No other preimpact mechanical malfunctions or failures were found with the airframe or engine. ## Factual narrative On September 10, 2023, about 1200 eastern daylight time, an experimental Sonex airplane, N569SX, was substantially damaged when it was involved in an accident near Dowagiac, Michigan. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. (Note: The accident time was estimated based on the departure time and nominal fuel consumption.) The pilot departed Dowagiac Municipal Airport (C91), Dowagiac, Michigan, about 1100, for a local area flight. An alert notice (ALNOT) was issued at 2021 when the pilot had not returned. The accident site was located 4 days later in a heavily wooded area about 4 miles north-northeast of C91. An open agricultural field was about 60 yards west of where the wreckage was located. There were no known witnesses to the accident. The airplane came to rest inverted. Trees in the immediate vicinity were up to about 100 ft tall. Fresh tree breaks and a downed tree were located about 30 ft north and 25 ft northwest of the wreckage, respectively. The aft fuselage was crushed and resting on a fallen tree. Both wings exhibited leading-edge crushing damage consistent with impact to the trees and terrain. The empennage was damaged consistent with impact forces. The flight control surfaces remained attached to the airframe, and control continuity was confirmed to the cockpit controls. The engine appeared intact and undamaged with the exception of minor impact damage to the air filter/intake assembly. The propeller was secured to the engine; however, both blades were damaged consistent with impact. The fuel tank was intact and contained about 10 gallons. The remaining fluid in the tank exhibited a blue tint and appeared consistent with 100 low lead aviation fuel. The fluid was clear and free of sediment. Figure 1 – Accident Site A postrecovery examination of the automobile engine revealed the ignition distributor rotor was fractured and separated from the driveshaft, as seen in figures 1 and 2. The interior of the distributor cap exhibited rotational scoring with fine powder residue but was otherwise intact. Each ignition harness lead was secure and undamaged. The engine examination was otherwise unremarkable. A new distributor cap and rotor were installed, and an engine test run was conducted. The engine subsequently started and ran normally at idle power. Figure 2 – Distributor Housing/Cap and Rotor Figure 3 – Distributor Rotor According to the Federal Aviation Administration, no ADS-B data associated with the airplane or the accident flight was available. At the time of the on-scene examination, the transponder was observed in the OFF position. The airplane was equipped with an emergency locator transmitter (ELT). However, the ELT unit was separated from its mounting cradle and the antenna cable was separated at the coaxial cable connector at the unit. The remaining portion of the cable and the airframe-mounted antenna appeared intact. The ELT switch was in theOFF position when initially observed by NTSB investigators at the accident site. During the postrecovery examination, the ELT was activated momentarily. The associated transmission was heard on an adjacent handheld transceiver tuned to 121.5 MHz. The Corvair engine had been installed on the airframe just over three years before the accident. The last condition inspection was completed on August 14, 2022, following a Sonex Condition Inspection checklist. While the checklist included checking the distributor cap for condition and continuity, it did not specifically list inspecting the distributor rotor. At the time of the inspection, the engine had accrued 47.5 hours of operation since installation. An autopsy of the pilot was performed by the Western Michigan University Homer Stryker M.D. School of Medicine. According to the autopsy report, the cause of death was blunt force injuries, and the manner of death was accident. Toxicology testing performed at the FAA Forensic Sciences Laboratory found no drugs of abuse. ## Aircraft - Registration: [N569SX](https://openairdocs.org/deregistered/N569SX-2024-08-27), registration cancelled 2024-08-27, S/N 0569, built 2005 (OpenAirDocs) - Reported make and model: SONEX AIRCRAFT SONEX - Registry model: [Martin Richard B SONEX](https://openairdocs.org/model/martin-richard-b-sonex) (registry code 05619AM) (OpenAirDocs) - Registry engine: [Amateur-built UNKNOWN ENG](https://openairdocs.org/engine/amateur-built-unknown-eng) (registry code 99999) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: 0569 - Year built: 2005 - Airframe hours: 391.1 - Engines: Corvair 100 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Condition, August 14, 2022 - Departed: C91, Dowagiac, MI - Destination: C91, Dowagiac, MI - Airport: C91, Dowagiac Municipal - Equipment: Electronic multifunction display ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 82; injuries: fatal; private; airplane ratings: single-engine land; medical: class 3, with waivers/limitations; seat: left; restraint: 4-point; toxicology performed; flight hours: 736 total ## Weather - Conditions: Visual (VMC), Day - Wind: 260° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 70 °F, dew point 61 °F - Altimeter: 30.18 inHg - Observed at: KBEH, 15 nm away - METAR: KBEH 101453Z AUTO 26005KT 10SM CLR 21/16 A3018 RMK AO2 SLP217 T02060161 53003 $ ## 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 20230910013629A](https://openairdocs.org/incident/20230910013629A), Sep 10, 2023: Martin Richard B SONEX, Dowagiac, MI, Substantial damage, 1 fatal. Narrative: On September 10th at approximately 1100 local time aircraft [privacy data omitted] an experimental / homebuilt piloted by a certificated private… ## Other investigations on N569SX (1) 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. - [NTSB CHI05LA158](https://openairdocs.org/ntsb/CHI05LA158), Jun 25, 2005: Martin Sonex (N569SX), Allegan, MI, substantial damage. Probable cause: The inadequate aircraft control by the PA-28-180 pilot while the airplane was stopped. ## Docket (10 files) The files NTSB released with the investigation on August 20, 2025, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=193066. 430 MB in all. - Examination summary (item 1, PDF, 6 pages, 179 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18768904&FileExtension=pdf&FileName=Examination%20Summary%20--%20CEN23FA410-Rel.pdf - Maintenance records -- airframe (item 2, PDF, 16 pages, 30.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18784850&FileExtension=pdf&FileName=Maintenance%20Records_Redacted-Rel.pdf - Maintenance records - engine (item 3, PDF, 8 pages, 291 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18784960&FileExtension=pdf&FileName=Maintenance%20Records%20--%20Engine_redacted-Rel.pdf - Record of conversation - helmholdt (item 4, PDF, 1 page, 67 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19009906&FileExtension=pdf&FileName=ROC%20--%20Andrew%20Helmholdt%20--%2017Sep2023-Rel.pdf - Investigation photographs (item 5, PDF, 5 pages, 1.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18809051&FileExtension=pdf&FileName=Photo%20Array-Rel.pdf - Memorandum for record a�� airport manager revb (item 6, PDF, 1 page, 79 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19009454&FileExtension=pdf&FileName=ROC%20--%20Oscar%20Azevedo%20--%2016Sep2023%20(RevB)-Rel.pdf - Engine test run (item 7, MP4, 21.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18784751&FileExtension=mp4&FileName=Video%20--%20Engine%20Test%20Run%20(Aircraft%20Owner)-Rel.mp4 - Fuel documentation (item 8, PDF, 2 pages, 83.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18783424&FileExtension=pdf&FileName=Fueling%20Documentation%20--%20N569SX_redacted-Rel.pdf - Toxicological report (item 9, PDF, 1 page, 166 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18744510&FileExtension=pdf&FileName=Tox%20Report_Redacted-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 10, PDF, 1 page, 730 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18784328&FileExtension=pdf&FileName=Release%20of%20Wreckage%20--%20CEN23FA410_acknowledged_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.