Sorry for the delay I`ve been playing with my tug.I`m perfectly aware of the hydraulic system architecture it`s written on 26vu in black and white [well green and blue so even old duffers like me can understand it], as for bringing up normal brake px thats routed via the crossfeed valve as you`d know , maybe i should have clarified, this will give you about 40seconds worth of brake use before px decays , although you may have hit the nail on the head if the brakeman was not trained correctly.Two incidents i`ve seen with aircraft deciding to go their own way have all been down to lack of hydralic pressure and not even size 10 safety boots would stop them . As for your comment captain that the aux pump is only there to just to take off the prop brake why have they designed it to run off the hot bat bus , to take the prop off you`d have to switch on the battery , a good idea from the French from a maintenance point of view , and if the small affair of an aux pump can repeatedly carry out undecarraige swings in the same time as an acw pump i`m sure it`ll stop a trundling ATR. It seems we`ve drifted from the original thread though as to why this happened .
Oh and xxtsgr both hyd pumps are of the conventional axial piston type , with a cylinder barrel containing 9 pistons the only difference being the flow rate of the acw is higher than the dc i learn`t that tugging around