Amateur-built Sopwith Baby accident near Lee'S Summit, Missouri, May 19, 2020
On May 19, 2020 at about 9:45 pm local time, a 2019 amateur-built Sopwith Baby, registered N41LR, was substantially damaged in an accident during takeoff near Lee'S Summit, Missouri (Lee'S Summit Muni 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 airplane builder's improper installation of the lower right wing which resulted in an uncommanded left roll and the subsequent loss of control.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- May 19, 2020 · about 9:45 pm local time
- Place
- Lee'S Summit, Missouri · Lee'S Summit Muni · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Amateur-built Sopwith Baby, built 2019
- Registration
- N41LR · registry record · serial 001
- Damage
- Substantial damage
- Flight
- Flight test · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot departed on the airplane's initial test flight in a tailwheel-equipped biplane. At the speed when the tailwheel lifted from the runway, the airplane began an uncommanded left roll. The pilot attempted to arrest the roll moment but was unsuccessful. He aborted the takeoff but lost control of the airplane as it settled down in a crab. The airplane exited the side of the runway and resulted in the failure of the left landing gear, and subsequent nose over of the airplane. The lower left wing sustained substantial damage. The airplane builder conducted a post-accident examination and reported that the right wing had a different "angle-of-attack" then the other wings, due to a construction error. This difference likely resulted in the uncommanded left roll during takeoff. This rolling tendency was not detected during the previous four high-speed taxi tests..
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 control on ground during takeoff defining event
The NTSB's findings
- cause Aircraft › Aircraft structures › Wing structure › Flight surfaces (wing) › Design
- cause Personnel issues › Task performance › Use of equip/info › Aircraft control › Pilot
Pilot
- Certificate: flight instructor, commercial pilot
- Ratings: multi-engine land; single-engine land; instructor: airplane single-engine; instructor: helicopter; instrument: airplane; rotorcraft: helicopter
- Flight time: 2,186 hours in all; 0.1 in this make and model; 4 in the last 90 days; 3 in the last 30 days; 1,345 as pilot in command; 105 on instruments
- Last flight review: February 12, 2020
- Medical certificate: Class 3 (with waivers/limitations)
- Seat: left
- Injury: no injuries
The aircraft
- Last inspection: annual inspection, January 31, 2020
- Maximum gross weight: 1,400 lb
- Seats: 2
- Landing gear: fixed
- Engine: Rotec 3600 (piston); 5 hours total
The flight
- Departed from: LXT Lee'S Summit MO at 9:45 pm
- Destination: LXT Lee'S Summit MO
- Flight plan: none
- Runway 36, 5,501 ft by 100 ft
Weather at the time
- Light: daylight
- Wind: from 010° at 3 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 68°F (20°C), dew point 52°F (11°C)
- Altimeter: 29.94 inHg
- Observation at 9:53 pm from KLXT
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
3 documents, released by the NTSB on July 24, 2020. 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 | Additional Information | PDF, 3 pages | View Download |
| 3 | Photos | 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.
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.