Let's have B777-300ER which has Main Tank Jettison Pumps INOP according to MEL 28-31-03. That means I have to use MEL 28-22-04 and deactivate Fuel Scavage System. In Operations part for Main Jettison pump is written
Limit the takeoff weight to the maximum climb limited landing weight at the departure airport, plus center tank fuel (which would be jettisoned during return-to-land procedure), plus 2,450 kg (for fuel that would be burned during a return-to-land procedure).
If I'm right the problem is performance during go-around in case of return, right? If so how can I get RTOW? I think it is only language problem but the MEL looks (for me) like I should calculate performace and RTOW and then lower it by fuel weight in CWT and by 2450 kg. But I think it is nonsense.
Operations part of MEL for Fuel Scavage System is quite clear. Add 1225 kg of fuel from CWT to ZFW. If I got it correctly it is the amount of fuel I can not get out of CWT because Scavage system is not working.
To confuse it even more what happens when one fuel jettison pump is working?