Servo-Surface

The BAC 1-11 AFCS, like that in the VC10, was based on the well proven Bendix PB-20 Autopilot and was designated the Series 2000 AFCS. New features over the PB-20 system include separate pitch and azimuth control computers, a modular Air Data Sensor and a range of units specifically designed for autoflare and autolanding.

Each unit in the BAC 1-11 AFCS is built to a common configuration with circuit modules arranged in stacks either side of the chassis. The stacks are connected by plugs to a mother board and are physically separated into ‘command’ and ‘monitor’ functions to preclude common failures. The computers are entirely solid state and there is a high degree of built-in-test. Self-monitoring techniques and multiple channel redundancy are used to give automatic failure survival in approach and cruise flight.