8Pieced Once in forward flight the F PUMP AFT caution appeared as it was running dry then the F PUMP AFT switch was switched off iaw normal procedure (but forgetting that he had forgotten to switch the F PUMP FWD switch back on in Dalkeith). Therefore, as each pump had been turned off at a time of dry running, subsequent emersion in fuel does not activate a F PUMP FWD or AFT caution again.
If I read you right, you try to establish how both pumps could end up off, due to recurring F PUMP FWD/AFT cautions.
I think your are not picturing the (presumed!) fuel management of most EC135 pilots correctly. If I'd ever get to pilot that a/c, my routine to those cautions would be - besides cussing - to always toggle both pump switches (e.g. FWD off + AFT on or FWD on + AFT off) in one single attentive manipulation, as there is no airborn szenario where I'd want both of them to be off.
This twin switch flipping would develop into a semiautomatic habit, I presume.