EAP's quadruplex-redundant digital flight control system is a development of that in the active control technology (ACT) Jaguar FBW test bed, the first digital fly-by-wire aircraft to fly without mechanical backup controls. The system has to withstand two critical failures. EAP has four identical flight control computers with no fewer than 13 control surfaces, the flight control computers will operate at more than three times the speed of Jaguar's. The Flight Control Computers house the flight resident software which stabilises the aircraft artificially then enables the pilot to fly it. In addition they house software for failure management, reversion logic, and built-in test.The Flight Control Computers are linked to EAP's two dual-redundant 1553B multiplex digital databuses. The avionics databus links the cockpit with the Ferranti FIN1070 inertial navigation system, Racal RA800 audio management system, GEC Avionics AD2780 Tacan, the flight control system, and the utility services management system (USMS). In addition, the Flight Control Computers process motion sensor information to provide data for the standby attitude and heading reversionary instruments.
Also included in the flight control system are two digital air data computers, four aircraft motion sensor units (AMSUs), and four actuator drive units (ADUs). While the foreplane, intake varicowl, and wing leading-edge flaps are driven directly from the flight control computers, the flaperons and rudder are driven from the aft-mounted ADUs which are connected to the computers by serial digital databus.
The air data and motion sensors are also connected to the computers along two dual redundant 1553B multiplex digital databuses. The AMSUs consolidate roll, pitch, and yaw rate sensors in single boxes.
GEC Avionics is responsible for EAP's flight control system, supplying the four flight control and two air data computers, while Bodenseewerk supplies the four actuator drive units, and Litef the four aircraft motion sensor units.
The Company, in common with other suppliers, made equipment for the EAP at their own cost in anticipation of orders for the Typhoon. Around 6 to 8 sets of equipment were made and all were put through the full evaluation/qualification tests.
