To get any electric powered hydraulic pumps to operate in the air, you need the engines to windmill fast enough so that the high speed rotor (N2 or N3) is above 50%. Engine electrical generators do not operate below this speed.
You're talking about the -400, then?
This isn't possible on the Classic, as the electricl pumps can't be powered in flight, nor can electricity be obtained from windmilling powerplants...it's hydraulics only with a minimum mindmilling speed of 160 KIAS, and no normal gear or flaps.