CM
The $64k question.
If I were wearing an old hat, the first question I’d ask is to establish the Design Authority responsibility. This is simple – the Boundary Control Document (or drawing) showing the new FADEC and its interconnects/interfaces. It isn’t always the case that a cable connecting two LRUs belonging to the same system is “owned” by the DA of that system. Often, the aircraft DA “owns” the cables, which complicates the boundaries. Often, the “input” cable belongs to one, the “output” to another. Regardless, the BCD would tell you that and direct the Technical Agency (the named MoD individual responsible for maintaining the build standard – safely) to the correct DA. And Commercial would know who to seek recompense from!
But there again, the Chief Engineer oversaw the dismantling of this process in the 3 years before MoK!