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

The power settings are implemented via the avionics system from the ground and aredependent on the available power and minimum and maximum permitted powersettings. The minimum power setting is based on the minimum power needed tomaintain the desired flight overnight and to maintain the motor temperatures withinacceptable limits. The maximum power setting (and thus the associated altitude) isdetermined by available power during the night, and the torque limit during the day.2.4 AvionicsThe avionics system provides a telecommand and telemetry capability mounted on theavionics master board, providing command and control of all aspects of the aircraft.On the ground there is an antenna which has a 5-degree beam width and tracks theaircraft using either GPS or direct signal power tracking. The main component of thecommunication system used for telecommand (flight command uplink) and telemetrydata downlink is the air data terminal. This unit has three main functions including:Receiving telecommand data transmitted from the ground control system(GCS) to the aircraft and forwarding the signals to the mechanisms onboard,Receiving telemetry data from the sensors and sending them to the GCS,Implementing a safety mode if signal is lost for more than 18 seconds.Once in flight, Zephyr can be flown either manually or via an automatic FlightControl System (FCS) (autopilot). The avionics system on board Zephyr collects datafrom all air sensors, the GPS, and the inertial measurement unit which measures the20