Re: 777 Flight Control System

From:         larryb@ssd.fsi.com (Larry Bellmard)
Organization: FlightSafety-SSD, Tulsa, OK, USA
Date:         21 Dec 94 02:17:42 
References:   1
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In article <airliners.1994.1774@ohare.Chicago.COM> suri@biz.ecs.umass.edu (Neeraj Suri) writes:

   Can anyone provide information (top-level/detils) on how the 
   flight control system for the 777 is set up? does it use identical
   software & hardware on all the six channels, how are the computers 
   interconnected etc. any information would be appreciated.

   neeraj

Here is a simplified description of whats going on.  The flight control
system is primarly made up of:
	3 - Primary Flight Computers (left, center & right PFC's)
        4 - Actuator Control Electronics (left1, left2, center & right ACE's)
        3 - Autopilot Flight Director Computer's (left, center & righ AFDC's)
        2 - Airplane Information Management System (left & right AIMS)
These LRU's communicate over 3 bi-directional ARINC629 busses (there are
only three "channels").  For the most part the matching LRU's run the
same software and the hardware would be identical.  The AIMS is the "mother",
providing communication "links" between any LRU's needing data from any other
LRU (if the two LRU's are on the same bus, communication may take place between
the LRU's).  So with a ton of inputs, the PFC determines where the control 
surfaces should be and tells the ACE to move the surface.  When the Autopilot
is engaged, the AFDC, then talks to the PFC and then the PFC talks to the ACE.
Sounds simple, try simulating it!!!!
--
Larry Bellmard                       FlightSafety International                  
Senior Engineer                      Simulation Systems Division                 
D69-Autoflight                       Tulsa, OK USA                               
larryb@dev1.ssd.fsi.com              918-251-0500