It's a fairly common tanker design to not reach MAX FOB without exceeding MAX TOW. You can't get anywhere near tanks full in a KC-10 for example. Fuel tank capacity is a function of volume - or the space available in the airframe. For the engineers it's probably more important that they avoid the situation where MAX FOB gives less than MAX TOW.
KC45 OEW was around 130,000KG. MAX FOB was 111,000KG.
MAX TOW still 233,000KG
Last edited by D-IFF_ident; 7th Nov 2014 at 15:59.
Reason: additional data