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Boeing 777 FCC Motherboard

Technical Information

Catalogue No: C0501
Category: Flight Control
Object Type: Module/Sub-Assembly/Component
Object Name: Boeing 777 FCC Motherboard
Part No: 6743-01109
Serial No: 013
Manufacturer: GEC Avionics
Division: Flight Controls [FCD]
Platform(s): Boeing 777
Year of Manufacture: circa 1987
Dimensions: Width (mm): 170
Height (mm): 270
Depth (mm): 25
Weight (g): 670
Location: Rack RAA03 [Main Store]

Type No 6743-01109
Ser No 013


This is a Motherboard from the Primary Flight Computer. It provides interconnection between the individual Circuit Modules to the Power Supply and to the unit connectors.

Initial studies of fault-tolerant avionics were conducted jointly with Cranfield in 1984, but the idea had been around in the company since the late 1970s. The research was directed at safety and economy in control, and particularly at effectively zero maintenance.
A Boeing request initiated the work, which had been going on for 21 months, continuing from some Boeing 7J7 fly-by-wire (FBW) prototype studies.
The target was a fit-and-forget electronic flight control system with a probability of total failure of the order of 10 to the power -10, and a 95 per cent dispatch probability even after 30,000 operating hours in situ.
GEC Avionics proposed an FBW control system based on three lanes served by three quadruple-element primary flight control units (PFCUs). Each uses a dissimilar processor, and each runs a software package that is dissimilar from the other two.
The configuration proposed consists of: Inmos Transputer T414 with Occam software, Motorola 88020 with Ada, and Intel 80386 with "C".
Each PFCU and its 12 cards is housed in a 10MCU Arinc 600 box and is to perform under passive cooling up to an environmental temperature of 85°C. The design maximises chip integration, avoiding internal connections, while external connections was minimised; the production PFC card count was reduced to five. 
The primary flight control computers (FCC) – sometimes referred to as primary flight control electronics (FCE) – are located in the aircraft electronic equipment (EE-Bay). Three FCCs are installed on the Boeing 777.
The FCC computes and transmits all normal mode primary flight control surface actuator commands (rudder, elevators, ailerons, flaperons, and horizontal stabilizer as well as the multi-functional spoilers and ground spoilers) to control and maintain normal flight for use by the actuator control electronics (ACE). The 7J7 programme was cancelled but the technology was transferred to the Boeing 777.

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