ed to protect against both electrical faults and equipment failure. Its creation was an evolutionary process that began with the Boeing 767 (Tenning 2.455). The newer aircraft has two separate electric generating systems, a main system and a backup system. Both systems have a generator on each of the propulsion engines. These integrated-drive-constant-speed generators distribute electric loads from left and right main buses. Except for the ability to switch to an external power source, the Boeing 777's electrical system is fully automatic (Andrade & Tenning 4-11).
The Boeing 777's electrical system employs dual (redundant) ARINC 629 communication buses. These advanced components are used for communication between control units and with other aircraft systems. Through ARINC 629 communication, these systems may be monitored and protected. Most importantly though, compared with previous buses, the ARINC 629 has fewer discrete wires. Consequently, the device is not only lighter, it also has fewer interface circuits. This enhanced simplicity reduces the likelihood of electrical malfunction (Andrade & Tenning 4-11).
One aircraft subsystem which may be prone to electrical failure is the avionics. In recent years, significant technological achievements by airframe, semi-conductor, and avionics manufacturers have led to the development of innovative avionics systems. These modern components currently employ large-scale integrated computing architecture. For example, this architecture is used in the Boeing 777's Airplane Information Management System. By minimizing the duplication of hardware and software elements, functionally integrated architectures decrease failure rates. In addition, high levels of functional integration generally provide "availability and integrity" which far exceeds "the requirements for distributed implementations (Morgan 9-12)." Therefore, these highly
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