I can only speak to the A-310 but I can assume based on that experience the same condition might exist on other Airbus aircraft. On the A-310 Command sensor unit there are two Cannon type connectors which can be interchanged. The only guard against misconnection is a small sticker on the connector and the connection that I believe says A or B. If these stickers come off the technicians can misconnect them. There is no outward manifestation of a problem but if the technician has to troubleshoot the system he will be driven crazy because he can’t find the problem.
The PPUs have the same problem in that the connectors are not keyed and can easily be interchanged. If this happens the computer will sense this and lock the system up.*** The wing tip brakes have the same problem as the CSU in that the connectors can be interchanged and troubleshooting will again drive the technician crazy.
The PCU solenoid connectors can also be interchanged and the only guard against that is the cables are tied back and the connectors are not keyed. If the tiebacks are cut for maintenance there is a possibility of misconnecting the connectors.
It is a part of any design specification that requires that connectors be keyed so that there is no possibility of misconnection. The manufacturer did not want to do this because of costs and a perceived schedule impact.
*** That’s if the computer is capable of diagnosing the problem but that’s another story.
