BMM389EC
With reference to you question on the Flap Schedule/Maneuvering Speeds, this is what boeing have to say.
" The flap maneuvering speed schedule provides the recommended maneuvering speed for various flap settings. When recommended procedures are followed, the schedule provides adequate buffet margin for an inadvertent 15 degree overshoot beyond the 30 degree bank.
The flap maneuvering speed schedule varies as a function of gross weight and will provide adequate maneuver margin above stall at all weights.
The schedule provides speeds which are close to minimum drag and in climb are close to maximum climb gradient speed. In level flight it provides relatively constant pitch attitudes and requires little change in thrust at different flap settings.
During flap retraction/extension, selecting the next flap setting should be initiated when reaching the maneuver speed for the existing flap position. Niormally the A/C should be accelerating when flaps are retracted to to the next position.
Acceptable maneuver margin is, however, retained at a speed 20 knots below the recommended speed."
With regard to the Hydraulic system
The fuel is required in the tanks to cool the Hydraulic fluid as it passes through the heat exchanger. A system, the excahnger is located in the # 1 fuel tank, while the B system exchanger is located in tank # 2.
A system pumps are engine driven pumps, while the B system are electric.
Boeing says that a minimun of 760 KGs in tank 2 for GROUND operation of B pumps.
I would think that the same limitation would be on the A system, but when would you have the engines running, to provide A system pressure with less than 760 KGs in the # tank?
Possible the B system limitation would be directed at Maintanance, while the A/C is under tow for eg.
Anyway thats my pennys thought