UAV - Unpiloted Aerial Vehicle
Flight Crew Instrument; Flight Crew Commercial
Flight Crew Last 90 Days 34.3; Flight Crew Total 2000; Flight Crew Type 180
Aircraft Equipment Problem Critical; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance
Flight Crew FLC complied w / Automation / Advisory
Aircraft
My UAV was conducting assigned missions at FL200 in accordance with a Certificate of Authorization issued by the FAA. At a point in the mission the UAV descended to FL190 without an ATC clearance. At the time of this violation; we lost a control link (Return Link Lost) with the aircraft. As we were then unable to verify the aircraft's position or obtain critical flight information; the command link with the vehicle was disabled releasing it on its Emergency Mission profile in accordance with the approved emergency checklist. The vehicle than began squawking 7600 and entered autonomous flight preceding direct to the assigned emergency mission loiter point and descended to a preprogrammed altitude of FL190.
The reporter advised that the (remote) command link with the UAV was lost for several minutes. This command link allows the aircraft to be flown by a PIC approximately 1;000 miles away using satellite relayed commands. It was this link that was lost and the aircraft was then released to its pre-programmed emergency rendezvous point where it would then be picked up visually and landed by on site operators. In this case the command link was regained after several minutes and the aircraft flown directly by the PIC to a point where it could be visually acquired by the on site crew and was landed safely. Maintenance investigation is then required to ascertain the reason for the lost link before the aircraft is again released for flight operations.
A government UAV lost the command link to its flight crew. Remote guidance was disabled and the vehicle was released to autonomous control for the balance of its flight.