Originally Posted by gr8shandini
I can't say I know much about Concorde. Did it use fuel for Mach trim?
Yes it did.
In the case of Concorde there was a significant shift aft of the centre of lift when going supersonic. Rather than trim using the control surfaces (with the resulting added drag), clever management of fuel burn, combined with fuel transfer aft (and forward during deceleration), was used to move the centre of gravity to the optimum position for most of the flight.
Concorde had a total of 13 separate tanks (carefully numbered 1 to 11, plus 5A and 7A... I bet somebody was superstitious...).
Tanks 9 and 10 (fully forward) and tank 11 (in the tail) were designated "trim tanks" and those were the ones used primarily to shift the CofG when needed.
CJ