The refueled tanks on ground are like beer bottles with the cap on. There is lot of air absorbed in it. As the aircraft climbs the atmospheric pressure keeps dropping which is like partially opened cap. The air keeps bubbling out and can create a vapour lock but due to the pressure created by fuel pumps the supply to the engine is not disrupted. By the time the aircraft climbs to FL 300 and above and stays there for at least 30 mts. all dissolved air bubbles out. So if fuel pumps fail now, the FL if above 300 can be maintained. If time spent was less than 30mts then you put the cap back on the bottle by descending to 300(higher pressure), if not climbed to 300 at all then there is lot more air in the fuel and you got to descend to even higher atmospheric pressure of 15000. If only one side pumps fail then you have to see if you are in gravity feed case. If not then initially cross feed for short duration but it will create imbalance. So you will have to compare that with extra consumption at lower level and choose the appropriate course.
Last edited by vilas; 15th Jan 2020 at 05:40.