Airbus: the tale of fault tolerant control

Flight Control Computers (FCC) take the pilot orders transmitted to the actuators by an arrangement of mechanical components to provide enhanced maneuvering characteristics. The control surfaces follow the FCC commands through electrical connections.

It implies that, the aircraft reliability is also dependent on the FCC performance. The FCC architecture is divided into a command channel and a monitoring channel:

1. The command channel provides the required computations for enhanced maneuverability and stability.
2. The monitoring channel supervises the components of the flight control system. It ensures that the control channel keeps operating correctly.

Along the years, commercial aircraft’s electrical flight control systems have changed. New technologies have evolved to fit aeronautical applications. One of the most important technologies is fault tolerant control. In this context, the concept of Fault Tolerant Control encompasses both command and monitoring of the aircraft operation.

Fault tolerant control compares signals from both control and monitoring channels to detect failures. This algorithm must be reliable enough to provide a tolerance to sensor inaccuracies and errors to prevent false alarms, but sensible enough to detect failures on time.