Amateur-built STOL CH701 accident near Byron, California, November 29, 2019
On November 29, 2019 at about 11:45 pm local time, a 2019 amateur-built STOL CH701, registered N701WJ, was substantially damaged in an accident during approach (VFR pattern base) near Byron, California (Byron Airport). It was a flight test under general aviation rules (Part 91). No one was hurt; 1 person was on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The pilot/builder's improper construction of the cowling, which resulted in inadequate venting of the engine, its overheating, and a partial loss of engine power.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- November 29, 2019 · about 11:45 pm local time
- Place
- Byron, California · Byron Airport · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Amateur-built STOL CH701, built 2019
- Registration
- N701WJ · registry record · serial 7-10529
- Damage
- Substantial damage
- Flight
- Flight test · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot stated that he fabricated and installed a cowling on the airframe prior to the flight. During the initial climb, the engine experienced a partial loss of power and the water temperature climbed above the maximum temperature. The pilot made a forced landing at the departure airport and encountered wind during the approach. The airplane was pushed off the runway and landed hard in the grass; the airplane came to rest inverted. The engine manufacturer provided instructions to builders to ensure there is proper venting over the engine. The pilot stated that he did not use any plans to build the cowling and did not perform any tests of the venting. The cowling was open on the bottom but did not have aft venting. As a result, the air pressure behind the radiator likely increased to be equivalent to that of the ram air, resulting in the engine overheating and experiencing detonation, leading to the loss of engine power.
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 approach (VFR pattern base) defining event
The NTSB's findings
- cause Aircraft › Aircraft power plant › Power plant › Engine cowling system › Design
- cause Aircraft › Aircraft power plant › Power plant › Engine cowling system › Incorrect use/operation
- cause Personnel issues › Task performance › Maintenance › Fabrication › Owner/builder
Pilot
- Certificate: private
- Ratings: single-engine land
- Flight time: 339 hours in all; 87 in this make and model; 36 in the last 90 days; 6 in the last 30 days; 297 as pilot in command
- Last flight review: October 23, 2018
- Medical certificate: Class 3 (with waivers/limitations)
- Seat: left
- Injury: no injuries
The aircraft
- Airframe total time: 115 hours
- Last inspection: condition inspection
- Maximum gross weight: 1,100 lb
- Seats: 2
- Landing gear: fixed
- Engine: Aeromomentum AM13 (piston); 115 hours total
The flight
- Departed from: C83 Byron CA at 11:42 pm
- Destination: C83 Byron CA
- Flight plan: none
- Runway 23, 3,000 ft by 75 ft
Weather at the time
- Light: daylight
- Wind: from 140° at 4 knots
- Visibility: 10 statute miles
- Sky: broken clouds at 7,500 ft; a few clouds at 6,000 ft
- Temperature: 52°F (11°C), dew point 37°F (3°C)
- Altimeter: 29.88 inHg
- Observation at 11:55 pm from KSCK, 19 miles away
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 June 7, 2022. 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, 11 pages | View Download |
| 2 | Records of Conversation | PDF, 1 page | View Download |
| 3 | Aeromomentum Engine Manual Excerpt | PDF, 6 pages | View Download |
| 4 | Post Accident Pictures (Provided by Pilot) | PDF, 2 pages | View Download |
The same docket at the NTSB · documents without a copy here are fetched from the NTSB when you open them.
Other NTSB records under N701WJ the same tail number, which may have belonged to a different aircraft at the time
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.