Thanks "Concerned LAME" I do recall talking about the standpipe in groundschool although of course, in our pilot book FCOM1, there is no system diagram that shows the standpipe only an implication it exists
:
The RAT automatically deploys, if both engines fail, or if there is low level in the green and yellow
or green and blue reservoirs.
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As for the HSMU controlled engine pump isolation valve - the books don't tell us - is it near the pump or up on the pylon i.e. could a catastrophic failure cut the green supply line above the shutoff valve?