Originally Posted by
tuna hp
Also, I can't imagine why a trijet would necessarily hold more fuel in the fuselage.
You don't have to imagine, just ask anyone who flies a 727 or DC10. Or even your local aircraft fueler for FedEX.
I've never been given an official explanation, but my best guess is that it is to give the number two engine it's own independent fuel source and prevent an imbalance situation that might result if it drew fuel from the wings. Someone correct me if I'm wrong.