Zephyr: A High Altitude Long Endurance Unmanned Air Vehicle ...

Simple payloads instructions without complex command and control requirements,such as only powering on and off, can be controlled directly from the avionics systemwithout the need for a payload controller PCB.2.7 Safety Cut Down SystemThe Zephyr aircrafts are fitted with a safety and containment system to ensure theaircraft remains within its allocated airspace. This system has two main functions, thefirst of which is to keep it flying within its allocated air space and the second is to cutthe aircraft down in a safe and controlled manner in the event of a permanent failurein communications between the aircraft and the GCS. These two functions arecovered by the safety waypoint mode and the cut-down mode.The safety waypoint mode is triggered if the command link is lost for more than a predefinedtime interval; for manual flight this is 4 seconds and for automatic flight thisinterval is 2 minutes. Triggering the safety waypoint causes the aircraft to fly towardsthat point and then loiter until communication is re-established. The location of thesafety waypoint is reviewed and can be updated during the flight in order to reflectnew meteorological conditions or in the event of the allocated airspace being changedduring flight.The safety waypoint can also be triggered by entering an invalid waypoint demand orin the event of the main avionics processor being reset. The safety waypoint triggercan be cancelled by sending a valid waypoint or heading, or by returning the aircraft25