Distributed intelligence, fault tolerance, and fiber optic technology hold significant promise when applied to complex sensor/actuator systems such as those found in primary and secondary flight control systems. This paper outlines the theory of operation and configuration of a fault tolerant distributed control system jointly developed by Raytheon Company and Beech Aircraft Corporation. The system's benefits accrue from the union of fiber optic performance advantages with the low cost of fault-tolerant distributed sensing and control techniques. The initial configuration is comprised of low-cost fault-tolerant computers which control, monitor and display the functions of two JT15D-5 engines and their thrust reversers across redundant fiber networks. Pilot inputs are transmitted digitally over a redundant fiber optic network using a distributed fault-tolerant processing architecture. In the Distributed Control-By-Light (CBL) system, low-cost intelligent nodes are placed at the site of the sensors, actuators, control inputs, feedback devices, and displays across the entire aircraft. The nodes communicate across redundant fiber optic networks using an industry standard open architecture protocol. Firmware at each node monitors or controls the local function and responds to commands from or passes digitized processed sensor data to other functions on the aircraft. Proven hardware and software fault-tolerance techniques are applied to provide the ability to withstand multiple faults. The Distributed Control-By-Light system achieves all of the benefits traditionally ascribed to FlyBy-Light: reduced cost and weight, reduced EM!, HIRF, and lightning susceptibility, reduced system grounding problems, reduced certification costs, and increased aircraft range and payload. The distributed architecture also provides decreased production and assembly costs, improved reliability, enhanced operational utility and decreased pilot workload, and enhanced maintenance and diagnostics capabilities.