Originally Posted by
HazelNuts39
The surprise for me is that apparently the special conditions under which the A320 was certified specify operational speeds such as V2 and Vref referenced to a Vs1g that can not be demonstrated with its systems operating as designed, i.e. in normal law.
If my recollection is correct, the systems were designed in such a way that each layer of control "laws" was implemented as a "wrapper" around the control law below it.
What this means is that the Direct Law implementation (where PFC commands are directly translated to the surfaces) serves as the operational "core" of the EFCS. What came to be known as the Alternate Laws (C* functions and soft protections) were built on top of the Direct Law core, and Normal Law (hard protections and tweaked rate functions) built on top of those.
As OG hints at, the software used in development, which would have occurred both on the A300 testbed and A320 prototypes*, would likely have had logical "hooks" linked to switches on the test consoles and possibly in the flight deck allowing for easy transfer between the different laws, modes and the two distinct implementations - not just for testing and certification purposes, but also as a failsafe safety measure should there be a significant software problem with the 'higher' level implementations during testing. The software used in production would be identical and still have those logical hooks - but would have nothing connected to them on the production aircraft.
* - Along with the A330/340/380/350 prototypes later on.