Pilot Debrief

Alisport SILENT 2 near Danbury, CT — 2019-06-04

Final reportERA19LA186
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Date
2019-06-04
Location
Danbury, CT, USA
Airport
DXR
Aircraft
Alisport SILENT 2
Registration
N66911
Category
Glider
Highest injury
Minor
Fatalities
0
Phase of flight
Descent

Probable cause

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.

NTSB narrative

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.

Analysis

Primary failure mode
Fuel management
First missed decision gate
Pilot should have managed battery power better before descending.

NTSB coding

Evidence available

  • FDR / data
  • Photos
  • 5 docket documents
View NTSB final reportView NTSB docket

Docket documents5

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