I understand that at diminishing airspeed there is an increasing EPR target that A/THR tries to set to set on the engine(s),
Yes, provided that both T/Ls are in the CLB detent.
but #2 was in CL detent, and surely one engine at CLIMB power would be enough to maintain 140kts even in CONF FULL.
Yes but remember that we are talking about a span of less than two seconds. In these two seconds, the #1 FADEC would have sensed that the delivered EPR has become less than it required given the FMGS / ADR requirements.
So I deduce that the limiting thrust lever EPR limit must have been that from thrust lever #1.
Each engine has its own -
independent- two-channel FADEC.What is computed on #1 FADEC may be - and generally is - different from what #2 does.
I don't have the ball park figure values on the Delta needed to trigger the A/THR disconnect (flying a different engine), I estimate it ~.2 EPR.
In resume, you would have to consider :
1.FMGS-->EIU-->FADEC--> = FADEC Target EPR
2.TLA---------->FADEC computed TLA/EPR
3.ADR--> + TLA----------> = EPR limit (depends on ambient conditions )
and compare them permanently.
People who can be confused with this architecture are people whose job is not a permanent contact with it. What is needed is a modicum of open-mindedness - sorely lacking in some parts of this forum !
The basic philosophy is "if you want the automatics, set them properly. If you don't, there are some warnings that will remind you to follow the correct procedure. If you insist,the automatics will disconnect and will deliver a configuration that's as safe as it can so that you can sort it out. And make sure that the warnings are unmissable and unmistakable".
Finally, there is still around the misconception that the CLB detent will deliver *Climb thrust*. Just treat it as a TLA at which the max achieved thrust will be CLB EPR on the conditions of the day.
In normal operations, a pilot will never see a climb EPR except after take-off, and then for a few moments, as the A/THR will then have engaged.