Originally Posted by
avionneta
does anybody know why in the airport analysis charts, the MTOW still increases below T ref. if it increases, it means more thrust is available but below Tref thrust is supposed to be constant (flat rated).
Ok, got it now. Yes, PLTOW (performance limited TOW) increases with temperature drop. It is not because of a thrust increase (there is no such thing - owing to the flat rating, as you correctly say) but rather to other variables in the equation. Thrust same? Yes - no changes. Lift same - No, a larger force available. Quicker acceleration to V1? Yes - lower energy at V1 - so less braking distance needed.
At the end: at rated temperature, say, 35 deg C ....... max permissible TOW 100 (%). ... at 05 deg C ..... same thrust, but better aircraft performance! Once all accounted for - higher max permissible TKOF weight!
FD (the un-real)