Messier-Bugatti has designed a particularly innovative alternate brake system, no longer hydromechanical, but based on the main circuit. The innovation is twofold: on one hand, the alternate circuit is also controlled electrically; on the other, it is controlled by a second computer: the ABCU (Alternate Braking Control Unit). The ABCU is also known as the EBCU (Emergency Braking Control Unit).Therefore, there are always two almost identical and totally independent hydraulic circuits, but each is now controlled by an independent computer. This is why the solution is known either as the "Full Brake By Wire System" or the "Full Electrical Braking System".
The ABCU handles a wider range of functions: for instance, it is capable of detecting a pressure drop in the normal circuit, causing it to shut down, and activating the alternate circuit. In this case, the ABCU reads the information coming from the sensors, makes the calculations and transmits the commands to the energy distributors, thus entirely taking over the role of the BSCU. The BSCU handles only antiskid control in this case. The advantages of this "full electrical" braking system (main circuit and alternate circuit) are numerous: lower weight, decreased cost, better reliability and improved maintainability, which is why an electrical alternate circuit is now systematically offered.
