@Contra I don't think this one is an 'error' worth propagating. In fact, we could just return and be quiet about it. The only thing we want to avoid is to actually send a trim while the drone is flying, since in the SDK they write that :"this command MUST NOT be sent when the AR.Drone is flying.". So, I would either return quietly, or show at least a warning. In this case the trace seems appropriate.