Good evening everybody.
In the B747-400 QRH I find the "HYD CONTROL 1,4" NNC.
Why is there no such checklist/advisory message for system 2 and 3?
I've tried to search for an answer to this question but without results, so this might be a no brainier for everyone else.
The only reason I might find is that demand pumps 1 and 4 are commanded ON when selector is in AUTO and trailing flaps are in transit or extended past "1". System 1 and 4 have some quite demanding tasks during takeoff and landing and loss of system pressure is maybe more critical.
Do anybody have some insight in this logic?
Best regards,
Bluescan