|Object Type:||Signal/Data Processor|
|Object Name:||Auto-Pilot Flight Director Computer|
|Year of Manufacture:||circa 1979|
|Location:||Archive Object Store|
The autopilot and flight director system comprises two self-monitored digital computers in a duplex configuration to provide safe low-level autopilot operation. The self-monitoring characteristics of the computers are utilised to achieve a high availability of the flight director as a reversionary facility should the autopilot fail. In addition, the flight director is extensively self-monitored.
All autopilot modes are therefore duplex, which gives additional failure protection throughout the flight envelope. The modes include attitude hold, heading hold, altitude hold (barometric), heading acquire, track acquire, Mach hold, IAS hold (autothrottle), auto approach, auto terrain following radar height hold and a pitch autotrim mode which controls the stick to the pitch trim position. It also feeds signal to the pilot’s instruments and Head Up Display to enable the pilot to monitor autopilot performance and to fly the aircraft manually if an autopilot malfunction occurs.
The system electronics, including power supplies and input/output interfaces, are housed in the two computers. The two processors, one in each computer box, are identical, but there are minor differences between the two computers in that Computer1 contains the consolidated triplex outputs to the CSAS, and Computer 2 contains the servo drives for both the autothrottle actuator and the pitch auto-trim actuator.
The processor logic is based on TTL ICs which are mounted on double sided printed circuit boards. The store components in the production equipment are bipolar type ROMs but in order to provide the capability for rapid change during flight test, erasable PROMs were be used in the development equipments. Marconi-Elliott Avionic Systems Limited has design leadership on the APFD programmes, whilst sharing the production with Aeritalia.
This system was designed to Spec SP-P-970162, and manufactured by Elliott/Aeritalia sometime after 1979.