Originally Posted by
gtseraf
on the 767, if one does not turn the hyd pumps on in this specific order, there is a chance that hyd fluid is transferred from one hyd system to another. I think the 777 is the same, hence the specific order. The 787 hyd pumps (electric) are inhibited until after engine start, so the switch sequence is irrelevant.
Doubley irrelevant on the 78, because on the 76 the hyd fluid transfer occurred by way of he the antiskid shuttle valve between R and C HYD systems (normal and secondary brakes). As the 78 brakes are electric this possibility does not exist. The switching sequence is retained for commonality.