CONCORDE SST

FUELSYSTEMS

Concorde, like most airliners, has multiple fuel tanks whcih are detailed below. The only difference is that during flight fuel is transfered from tank to tank to maintain trim and balance of the aircraft as it does not have a full tailplane which would be used on a subsonic airliner to perform this task. Also for supersonic flight the Center of Gravity is critial and required to be moved for different speeds.

The fuel is also used as a heat sink for cooling purposes. Surplus heat from the air conditioning and hydraulic systems from the constant speed drive and generator and also from the engine lubricating oil is rejected through heat exchangers to the fuel.


FUEL TANKS
Location of Concorde's fuel tanks.

Function

Tank Number

Capacity (litres)

Quantity (kg)

Engine supply

1

2

3

4

5,300

5,770

5,770

5,300

4,198

4,570

4,570

4,198

Main
Storage
Tanks

5

6

7

8

9,090

14,630

9,350

16,210
7,200

11,587

7,405

12,838
Auxiliary Tanks

5A

7A
2,810

2,810
2,225

2,225
Transfer and Reserve Tanks 9

10

11
14, 010

15,080

13,150
11,096

11,943

10,415
Totals 119 ,280 94,470

Center of Gravity and Fuel Transfer

As mentioned above the centre of gravity (CoG) on Concorde it critical to it being able to maintain supersonic speeds and also fly successfully at low speeds. The centre of lift of the aircraft, when flying at Mach2, can move by some 6 feet. On a traditional subsonic aircraft the control surfaces (or entire tailplane) would be moved to trim the aircraft correctly, but on Concorde this would be unacceptable due to the drag it would cause and also leave very little movement left to control the aircraft.

The way the change in the centre of lift from the wings is trimmed out on Concorde is to compensate by moving the weight distribution, or CoG, by pumping fuel from the forward trim tanks to the rear trim tanks and vice versa. The trim tanks make up around 33 tons of fuel that can be moved around the aircraft. (the main tanks hold 95 tons).

Before take off and during the acceleration through Mach1 to an eventual Mach 2, fuel is pumped out of the forward trim tanks to the rear trim tanks and the collector tanks in the wings. Around 20 tons of fuel is moved in the process and results in a rearward shift of the CoG by 6ft (2 meters.)

At the end of the Cruise during the deceleration fuel is pumped forward to the wing transfer and even the forward trim tanks is necessary thus moving the CofG forward again as the centre of lift moves reward. Once on the ground it is standard practice to then pump more fule into the forward trim tanks to correctly balance the aircraft, so it can be unloaded without any stability problems and the chance of it becoming a "tailsitter"

The Movement of fuel also provides additional benefits at lower speeds: By making the aircraft rearward heavy during take off and landing, this causes the elevons control surfaces to move downwards to counteract this weight and in so doing so increases the camber of the wing generating more lift at slower speeds. Another feature is the ability to move fuel across the aircraft between tanks 1 and 4. This allows the aircraft roll trim to be set without having slightly different deflection on the elevons, which again adds drag and reduces performance.

The full transfers on Concorde are carried out by the flight engineer from his fuel control panel. On Concorde this is one of the most important and time consuming jobs for the engineer. The panel allows the engineer to set up the transfers to be carried out automatically and stop when the relevant quantities of fuel have been moved to the correct tanks.

The following table shows the corridor for where the center of gravity on Concorde must be for different speed profiles.

During flight, dynamic markers or "bugs" are shown on the Centre of gravity displays that feature on the instrument panels. These show the pilot what the CofG limits are for the speed the aircraft is currently travelling at. Bugs are also shown on the airspeed indicators (Mach and IAS) that show what speeds can be flown for the current Centre of Gravity position.

Fuel movement diagrams and specific infomation based on an extract from "Flying Concorde" by Brian Calvert.
CofG corridor diagram supplied by Peter Baker, former Concorde test pilot.