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

navigation via GPS, and ground track following waypoint navigation. All arecontrollable from the GCS through the transmission of new angle of attack/pitch/roll,heading or waypoint commands as appropriate. Rate of climb is always controlledmanually from the GCS via the motor power demand. The flight crew monitors theaircraft 24 hours a day and manual override of the automatic flight control system ispossible at anytime from the ground in case it needs to be used, but in practise theaircraft is usually flown by the autopilot.Forward looking pilot cameras onboard the aircraft are used to assist in take-off andlanding, to detect the horizon and cloud details during day and night. These camerashelp to assist the pilot in navigation and help to monitor the FCS performance.2.5 Ground Control SystemThe Ground Control System, GCS, consists of a group of ground antennas andportable cabins from which the aircraft is controlled. The primary systems found inthe cabins are a Ground Data Terminal (GDT), Flight Critical Computer (FCC) and asystem of computers operating via a Local Area Network for increased command,control and mission planning ability. The antenna systems, GDT and FCC are theonly flight critical components necessary for maintaining control of the aircraft andtherefore a completely separate duplicate system is running in case there is a failurewith one of the critical components. An uninterruptible power supply ensures that ifthere was a temporary loss of main electrical power to the GCS, it will not jeopardisethe mission.22