Concorde was exactly the same as any other aircraft in that it would be loaded in such a manner that with zero fuel the aircraft's C of G would be within the landing limits.. If this was not possible then ballast fuel has to be loaded[ or any other form of ballast] so as to achieve this C of G. This ballast fuel however must not form part of the fuel burn or diversion fuel
With the above in mind all fuel on Concorde was useable fuel but during some part of the flight prior to being burnt it it would be used for varying inflight regime trimming.
Now prior to landing the F/E would pump a predetermined amount into tank 9 so as to achieve a C of G fwd of 53.5 % for landing. This was only required because there was still fuel on board. If the aircraft was held before landing and the fuel QTY dropped he would pump this fuel out of tank 9 and into the engine feed tanks as it was no longer required for C of G purposes
Therefore yes Concorde could safely land from a C of G point of view with no fuel.
And around four tonnes WAS transfered into tank 9 after landing, in order to aid ground stability, particularly during disembarkation.
landlady
There was nothing magical about 4 Tonnes in tank 9, and in fact it usually was too much for stability reasons, but for simplicity a single big figure was used. In fact if it was not possible to put 4000kgs in tank 9 [due to lack of fuel]then the flight deck crew were instructed to remain on the flight deck until the passengers had got off and the rear hold had been emptied. Now some of us flight deck crew helped more than others in this
