Primary Tx/Rx Failure
All the UAVs we build contain aero-modeler-based primary control systems to enable manual flight of the aircraft within the line of sight of the pilot. Since the systems used are mass produced and subject to very extensive user testing, these systems are typically very reliable provided they are carefully installed and they are used within the ranges specified by the manufacturers. In the UK, operators of aircraft using such systems are required to carry out range tests at reduced power settings before flight operations to ensure that radio communications are unlikely to be interrupted. The user must also set the fail-safe mode of the aircraft so that if communications fail, the aircraft enters a known and safe mode of flight, typically at low power with a shallow spiraling descent. This aims to prevent the aircraft flying away from the pilot and also to reduce flight speeds to minimize any damage caused in the event of uncontrolled ditching. To add to resilience, it is also possible to fit dual primary control receivers to the aircraft so that if one receiver fails, control is automatically handed to the second, though this, of course, makes the switching unit a single point of failure.