UAV - Unpiloted Aerial Vehicle
Flight Crew Last 90 Days 14.3; Flight Crew Total 170.1
Situational Awareness
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Landed in Emergency Condition; General Flight Cancelled / Delayed
Aircraft; Chart Or Publication
I was the unmanned aerial system pilot-in-command. The rest of our crew consisted of a UAS operator and two ground station operators monitoring research data collected by the UAS and UAS altitude and airspeed data. The flight was conducted under part 91; with a certificate of authorization to operate up to 5000 feet. The standard flight profile for our operations with this unmanned aircraft consists of a stepped climb up to 6200 feet; and then a constant descent to land. Equipment on board the aircraft measures atmospheric parameters such as CO2 levels; temperature; relative humidity; and wind speed and direction throughout the profile. On the incident flight; we flew a different profile; consisting of a constant climb up to 6200 feet; and a stepped descent down. The takeoff and initial climb proceeded normally. As the aircraft climbed through approximately 3700 feet; we observed a long plume of white smoke start emitting from the aircraft. The emission lasted for approximately two seconds. The aircraft immediately lost engine power; but the control surfaces were still functional. The operator was able to glide the aircraft to a landing without further incident. The smoke plume was caused by the aircraft's electronic speed controller (ESC) burning out. There was no visible damage to the outside of the ESC; but we inferred there is significant internal damage as it was no longer functional after the incident. There was no damage to the battery or to the airframe. There were no injuries and no damage to property on the ground. Immediately after landing; I reported the incident to the NTSB Response Operations center telephone line. I believe the incident was caused by the prolonged climb which may have overheated the ESC; or possibly by use of an ESC with an incorrect amperage rating. As a corrective action; we may have to adjust the profile to avoid such prolonged climbs in the future. We could also reposition the ESC in a location which receives more cooling airflow.
A UAV Pilot in Command not flying reported the UAV lost power and was glided to a landing.