Amateur-built SONEX accident near Auburn, Washington, January 16, 2024
On January 16, 2024 at about 7:30 pm local time, a 2013 amateur-built SONEX, registered N920MB, was substantially damaged in an accident during initial climb near Auburn, Washington (Auburn Municipal Airport). It was a personal flight under general aviation rules (Part 91). No one was hurt; 1 person was on board or involved. The weather was visual conditions (good weather).
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The NTSB's probable cause their words, unchanged
Water contamination within the fuel regulator air-reference system, which resulted in improper fuel metering and a loss of engine power during initial climb.
Source: NTSB aviation accident database, copy made October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- January 16, 2024 · about 7:30 pm local time
- Place
- Auburn, Washington · Auburn Municipal Airport · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Amateur-built SONEX, built 2013
- Registration
- N920MB · registry record · serial 1145
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot of the experimental amateur-built airplane experienced a partial and then total loss of engine power shortly after takeoff. The pilot performed a forced landing onto a road, where the airplane collided with a signpost and sustained substantial damage. Postaccident examination revealed no mechanical anomalies with the engine or airframe fuel delivery system that would have precluded normal operation. However, water was found within the throttle body injector air-reference line and regulator diaphragm. This contamination likely led to inadequate fuel regulation, resulting in the power fluctuations observed by the pilot and eventual power loss. The investigation could not determine how water entered the system.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
What happened, in order
- Loss of engine power (partial) during initial climb
- Loss of engine power (total) during initial climb
- Powerplant sys/comp malf/fail during initial climb defining event
The NTSB's findings
- Aircraft › Aircraft power plant › Engine fuel and control › Fuel controlling system › Damaged/degraded
Pilot
- Certificate: private
- Ratings: single-engine land
- Flight time: 699 hours in all; 118 in this make and model; 28 in the last 90 days; 6 in the last 30 days; 699 as pilot in command
- Last flight review: October 19, 2023
- Medical certificate: Sport Pilot
- Seat: left
- Injury: no injuries
The aircraft
- Airframe total time: 219.4 hours
- Last inspection: condition inspection, May 10, 2023; 71.3 hours since
- Maximum gross weight: 1,150 lb
- Seats: 2
- Landing gear: fixed
- Engine: Aeroconversions AeroVee (piston); 219 hours total
The flight
- Departed from: S50 Auburn WA at 7:28 pm
- Flight plan: none
- Runway 35, 3,842 ft by 75 ft
Weather at the time
- Light: daylight
- Visibility: 10 statute miles
- Sky: broken clouds at 23,000 ft; scat at 18,000 ft
- Temperature: 34°F (1°C), dew point 7°F (-14°C)
- Altimeter: 29.97 inHg
- Observation at 11:53 am from KSEA, 30 miles away
Weather report (METAR): KSEA 161953Z 00000KT 10SM SCT180 BKN230 01/M14 A2997 RMK AO2 SLP159 T00061144
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
4 documents, released by the NTSB on February 11, 2026. View them here, or download them; the NTSB redacts some personal details before release, and this site shows the NTSB's own titles rather than its file names.
| # | Document | What it is | |
|---|---|---|---|
| 1 | Pilot/operator Aircraft Accident Report, NTSB Form 6120.1 | PDF, 9 pages | View Download |
| 2 | Engine Examination Report | PDF, 8 pages | View Download |
| 3 | Release of Aircraft Wreckage, NTSB Form 6120.15 | PDF, 2 pages | View Download |
| 4 | Evidence Control Form | PDF, 1 page | View Download |
The same docket at the NTSB · documents without a copy here are fetched from the NTSB when you open them.
About this page
Everything above comes from the NTSB's public accident database: the narrative, probable cause and findings are the NTSB's own words, and the coded tables behind its report (pilot, aircraft, flight, weather, injuries, sequence of events) are written out in plain English. Pilots' ages, home towns and medical details are left out on purpose. The documents and photographs are the NTSB's docket, the folder of records gathered during the investigation, shown as the NTSB released them (the NTSB redacts some personal details first) and listed under the NTSB's own titles. This site's own text never names pilots, passengers or anyone else involved. A preliminary report describes what is known soon after the event and can change; the final report, with the probable cause, usually follows one to two years later and this page is refreshed when it does. Case number WPR24LA074.