Originally Posted by peteryu
1. All the systems are functioning normally and a FTS command via the telemetry link would instantly activate the FTS.
2. The link is lost and the UAV enters Loss-of-Comms mode autonomously.
The problem is that in the second scenario, there is no way to trigger the FTS if the plane is clearly malfunctioning. The only possible thing that can trigger the FTS in Loss-of-Comms mode is the Geofencing system. If the plane was flying out of control but still within the boundaries, there would be no way for trigger the FTS.
I think that is covered adequately by the 5.5.2 loss of data link wording. If you have lost comms but are within the mission boundary then the plane must follow a series of steps to try and re-establish comms. Those steps have time limits -- 10 sec initial timeout on link loss, flight to comms hold, 2 minutes loiter at comms hold, flight to airfield home, 2 minute loiter at airfield home, then if you still don't have control you can do a "controlled termination" which can include an automated landing.
So in the situation you describe safety is maintained by 2 mechanisms:
1) the geo-fencing is active the whole time. If it goes outside the fence it terminates
2) the time limits to re-establish comms mean that it will eventually recover or terminate
Even if all of the comms logic didn't work the plane will eventually run out of fuel/battery and crash within the mission boundary. That would be annoying, but wouldn't be a safety risk.
So I think its reasonable to assume that a separate radio link dedicated to flight termination isn't needed, which is what we will assume unless one of the organisers posts a clarification.