DATA BUS TECHNOLOGY APPLICATIONS - BOEING-777 AUTOTHROTTLE SERVO MOTOR

On the Boeing 777 aircraft, two autothrottle actuators are required, o ne for each throttle lever, both controlled by either one of two compu ters. The consequent potential need for four remote servo-amplifiers h as been eliminated by using two 'smart' autothrottle servo motor units (ASMs) independently controlled by ARINC 429 data bus rate command si gnals from the active computer. The development of the B777 ASM from a servo motor unit used on B727 is recounted and the ASM design and ARI NC 429 data bus control architecture are described in detail.