Evolution of the Boeing 777 Electrical Power System

The design of the Boeing 777 electrical power system was an evolutionary process beginning with an up-rated version of the 767 electrical power system architecture, leading to a configuration with several new and innovative features. One of these was support for triple channel Category IIIb autoland with one engine inoperative following dispatch with one main generator inoperative. The Boeing 777 electrical power system was designed from the start to support extended-twin-overwater-operations (ETOPS), as opposed to having this capability added later by modification. As a result, the ETOPS capability was designed as an integral part of the AC and DC electrical distribution network. The evolution from the 767 configuration also incorporated the following new features: (1) providing power to the Captain's flight instruments (in addition to the standby flight instruments) with all engines out, (2) providing power to the first officer's flight instruments after loss of all main generators, i. e., ETOPS, (3) simplification of power transfer switching, (4) providing no-break power transfer, (5) enabling ground operations at full galley loading by simultaneous use of the APU generator and external power, and (6) providing for two external power receptacles.