UAV - Unpiloted Aerial Vehicle
Flight Crew Last 90 Days 100; Flight Crew Total 10238; Flight Crew Type 4618
Aircraft Equipment Problem Critical; Ground Event / Encounter Loss Of Aircraft Control; Ground Excursion Runway
General None Reported / Taken
Aircraft; Procedure
Aircrew got into the seat to launch the aircraft. Normal pre-flight operations; but once crew got link with the aircraft; the chiefs loaded new DLI keys onto the plane without telling any of the aircrew about the new procedures.  This caused over an hour of trouble shooting in order to establish link with the aircraft.  The GCS maintenance guys reloaded the DLI keys into the GCS; but the crew was still unable to establish link with the aircraft again. Aircrew had seen some abnormal readings from the GCS about the aircraft being at [Altitude] when the crew had no link with the aircraft; same with the RPM (108.7) and Uplink sig 1 (112.4%).  The Maintenance crews were able to finally get the correct DLI keys loaded into the aircraft.  Aircrew completed all checklists up to the C-band link test.  At that point the RX2 when checked would send the aircraft lost link.  Aircrew had maintenance swap to a new GDT; which fixed the problem and the C-band link check completed fine.Crew completed the rest of the launch procedures without any problems.  During the taxi out to Runway XX; aircrew started getting  'LOS UPLINK Secondary - LOST' warning.  There were no indications of anything being wrong with the link.  Crew kept an eye on the systems to make sure there wasn't any problems with any of the links.  At the time there was nothing showing that there was anything wrong.Aircrew was cleared to line up and wait on Runway XX.  Once the crew lined up and waited the aircrew got the same warning as before.  The warning did clear; so once the aircrew got clearance to take up the crew did.  Right after the 50 kt. call; the warning came back up.  Pilot decided to continue the take off; but shortly after that; the primary uplink was lost. Sensor called out lost link.  Pilot aborted; sensor responded with abort; abort; abort.  Shortly after sensor reminded the pilot to match settings just in case the aircraft did get airborne.  During this time the crew still had no control of the aircraft.  Aircraft departed the prepared surface.  Aircraft came to a stop after Taxiway X with engine off.
UAV pilot reported the primary uplink was lost causing a remotely controlled aircraft to suffer a runway excursion during takeoff.