UAV - Unpiloted Aerial Vehicle
Flight Crew Commercial; Flight Crew Instrument
Flight Crew Last 90 Days 60; Flight Crew Total 2300; Flight Crew Type 100
Communication Breakdown; Human-Machine Interface
Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued Advisory / Alert; Flight Crew Regained Aircraft Control; Flight Crew Returned To Clearance
Human Factors; Weather
I requested a climb from FL190 to FL250 to climb above weather. Before entering into a climb I asked the Second Officer to perform a full sweep with the camera to look for cloud location and adverse weather. None was noted.Climbing through FL210 conditions were encountered that affected the performance of the aircraft and resulted in a loss of altitude from FL210 to 16;500 MSL. Due to my efforts to fully regain positive control of the aircraft I was unable to declare an emergency as the main concern was to regain positive control of the airplane and prevent further descent. As soon as I regained positive control I initiated an immediate climb to the cleared altitude of FL250. ATC advised of the deviation in altitude. I advised ATC that the descent was due to weather and the aircraft currently in a climb to FL250. The flight level request was amended to FL290 in order to fly above weather.
While attempting to climb above weather the pilot of a UAV lost control of his aircraft at FL210 and lost altitude to 16;500 MSL before regaining control and restarting the climb.