@Boom, thank You for the answers. Together with the picture of the quadrant, it does seem to point into a certain direction.
1. The propellers feathered at the same time the flaps were supposed to go to 30. It stretches my imagination a bit to assume an unscheduled feather to strike both engines right at this time, without autofeather armed and bypassing all the internal safety nets such as the mentioned lockout on the far engine.
2. Looking at the quadrant, not only are the flap lever and the condition levers right beside each other. Also, their respective position may well have been quite similar. I obviously stand to be corrected here, but I gathered that the condition levers are normally in "AUTO" in this flight phase - the flap lever was in position 15°, so they were rather adjacent to each other. Additionally, the required travel from 15° to 30° on the flap levers seems rather similar to the travel from AUTO to FTR on the condition levers. The haptic differences between two versus one lever and the very different unlatching actions seem to be the only remaining 2 cheese layers that prevent a misselection in a rather high-workload situation in which the often-performed selection may be performed without looking at what lever is being grabbed.
About the engines and their connection to the hydraulic pumps, as the question was asked: On a PW120, the hydraulic pump is mounted on the propeller reduction gear box along with the variable frequency AC generator and other things. The turbomachinery drives the DC starter generator that generally speaking provides the low(er) watt systems. If one propeller is feathered and the other is running, the good engine will provide power to the failed engines hydraulic system in some way (be it via an AC electric auxiliary pump or a unidirectional PTU), but with all engines feathered, hydraulics will generally end up unpressurised, whether or not the turbomachinery is still running.
Last edited by Tu.114; 16th February 2023 at 11:37.