Alisport SILENT 2 accident near Danbury, Connecticut, June 4, 2019
On June 4, 2019 at about 9:00 pm local time, a 2016 Alisport SILENT 2 (glider), registered N66911, was substantially damaged in an accident during approach near Danbury, Connecticut (Danbury Muni airport). It was a personal flight under general aviation rules (Part 91). 1 person had minor injuries. The weather was visual conditions (good weather).
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The NTSB's probable cause their words, unchanged
The pilot’s inadequate inflight management of the motor glider’s available battery power, which resulted in the inability of the electric motor to provide sufficient thrust to sustain flight in an environment where no atmospheric lift was available.
Source: NTSB aviation accident database, copy made October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- June 4, 2019 · about 9:00 pm local time
- Place
- Danbury, Connecticut · Danbury Muni · map
- Type
- Accident
- Injuries
- 1 person had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Alisport SILENT 2 ELECTRO, built 2016 · all SILENT 2s on the register
- Registration
- N66911 · no longer on the register · serial 2079
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot was conducting a personal flight in an electrically-powered, self-launching motor glider. He stated that, while returning to the departure airport at the conclusion of the flight, the glider encountered sink and he turned on the electric motor, but it produced “no thrust.” The glider continued to descend and impacted a house about 2 miles from the airport, resulting in substantial damage. The pilot reported that there were no mechanical failures or malfunctions with the glider that would have prevented normal operation before the accident and that the accident might have been prevented with “better management of power and understanding of battery power source.” Data from the engine control unit indicated that the motor was used for about 13 minutes during the taxi, takeoff, and climb. The motor was used again about 5 hours into the flight for about 19 minutes, and again about 5:49 hours elapsed flight time, for about 32 minutes. The final activation of the motor occurred at 6:21 elapsed flight time; the accident occurred at an elapsed flight time of about 6:22. According to the glider manufacturer, the battery supplied power for takeoff and an additional 40 minutes of use thereafter. During the accident flight, the motor was used for a total of over 1 hour. Given this information, it is likely that the pilot had exhausted the available battery power and that the motor was no longer able to provide sufficient thrust to sustain flight.
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 lift during approach
- Fuel exhaustion during approach defining event
The NTSB's findings
- Personnel issues › Action/decision › Info processing/decision › Decision making/judgment › Pilot
- Aircraft › Aircraft systems › Electrical power system › Battery/charger › Incorrect use/operation
Pilot
- Certificate: private, sport pilot
- Ratings: single-engine land; rotorcraft: glider
- Flight time: 514 hours in all; 10 in the last 90 days; 10 in the last 30 days; 514 as pilot in command
- Last flight review: December 18, 2018
- Medical certificate: Sport Pilot
- Seat: sngl
- Injury: minor injuries
The aircraft
- Airframe total time: 200 hours
- Last inspection: condition inspection, March 5, 2019
- Maximum gross weight: 691 lb
- Seats: 1
- Landing gear: fixed
- Engine: Lz Design FES (electric); 17 hours total
The flight
- Departed from: DXR Danbury CT at 4:30 pm
- Destination: DXR Danbury CT
- Flight plan: VFR
- Runway 26, 4,422 ft by 150 ft
Weather at the time
- Light: daylight
- Wind: from 240° at 11 knots, gusting 16
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 68°F (20°C), dew point 39°F (4°C)
- Altimeter: 30.01 inHg
- Observation at 8:53 pm from dxr, 2 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
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 ERA19LA186.