Autothrottle Computer

Technical Information

Catalogue No: C0609
Category: Engine Control
Object Type: Signal/Data Processor
Object Name: Autothrottle Computer
Part No: 42-001-01
Serial No: 04
Manufacturer: Elliott/SFENA Consortium
Division: Unknown
Platform(s): Concorde 
Year of Manufacture: circa 1967
Width (mm):
Height (mm):
Depth (mm):
Weight (g):
Location: Archive Object Store

Elliott SFENA
Consortium Design
Elliot Bros (London) Ltd
Rochester Kent England
Unit: Autothrottle Computer
Type 42-001-01
Serial 04


Computing circuits and power packs which constitute the Concorde automatic flight control system were packed into eight basic computers (2 off each), namely:
● Autopilot and Flight Director Pitch Computer;
● Autopilot and Flight Director Azimuth Computer;
● Autostabiliser Computer;
● Autothrottle Computer;
● Electric Pitch Trim Computer;
● Warning and Landing Display Computer;
● Safety Flight Control Computer;
● Item Computer.

The computing circuits were split into modules which are arranged in stacks either side of the chassis assembly. These stacks were located together by plugs which also provide a means of inter-connecting the individual modules and connecting the modules to a mother-board mounted on the chassis. These mother-boards were connected to the cableforms which run to the rear aircraft connectors and front test connectors.

The box was physically segregated in to command and monitor computing areas to preclude common failures. The solid state logic switching circuitry was incorporated in the centre segregation spline.
The electronic implementation was based on standardised micro-electronic linear computing elements with external components to set gain and transfer functions. Electromechanical integrators were eliminated and digital integration was used when long term storage of datums was required. All switching was solid state except where total electrical isolation or filament drivers were involved.

The computers included built-in test circuitry which was aimed at satisfying airworthiness requirements prior to take-off and fulfilling the first line maintenance objectives. Additional test points are provided on the front of the computer to facilitate fault location to module level at the intermediate servicing stage.

The barely legible, hand-written paper label seems to read: Concorde; FCSD ELS.

The visible module's part numbers are:
7618-00008 (Rate Limit Amplifier)
7622-00017 (Lever Position Amplifier Module)

Early in 1963 joint proposals were made, together with Bendix, for a flight control system for a proposed supersonic civil transport. This was the forerunner of what became the 'Concorde'. When Anglo-French agreement was reached for joint development of the 'Concorde', a formal agreement was made and Elliotts led a consortium with SFENA and Bendix.  The Automatic Flight Control System included five systems, Automatic Pilot, Flight Director and Take-Off Director Computers, Automatic Throttle, Pitch axis Trim and Three Axis Autostabilisation.

Concorde was controlled in pitch and roll by Elevons and in yaw by Rudders. Each control surface is operated by a Power Flying Control Unit (PFCU).

The three Elevons, on each side of the aircraft, were in two groups; the outer and middle Elevons because their deflection angles were always synchronised, and the inner Elevons because their deflection angles in the roll axis are less than that of the outer and middle Elevons.

Conventional flight deck controls actuated three signal channels; two electrical and one mechanical.

Each electrical flying control channel was supplied from its own inverter which operated at a different frequency from the main aircraft system. On both electrical channels the pilot control movements generated, by means of synchro transmitters called resolvers, electrical signals that directly controlled the PFC servos. Each flight control group, (middle and outer elevons, inner elevons, and rudders), operated independently through its own resolvers, which also provided the pitch and roll mixing for the elevons.

The Mechanical channel also transmitted pilot control movements to the PFC servos but was unclutched at the servos when either of the electrical channels was operating.

Three control signals; two electrical and one Mechanical, were therefore available at the PFC servos, but only one was activated at any one time by the monitoring system that monitored the operation of the control surfaces by groups.

On the Mechanical channel of each flight control axis, pilot control movements were transmitted to the PFC servos by linkages and cables through a Relay Jack that compensated for linkage inertia.

Pitch and roll inputs were mixed by a mechanical mixing unit downstream of the pitch and roll relay jacks.

The monitoring system monitored:

Flight control inverters
Hydraulic systems pressure to the flight controls
Operation of the servo controls
Operation of the electrical control channels
The monitoring system automatically rejected a flight control channel suffering a failure in these systems and changed to the next available channel.

Concorde also had an Auto-Stabilisation system which improved the natural stability of the aircraft. It minimises the effect of turbulence and reduced the resulting flight path disturbance following an engine failure. The system comprised two separate channels for each of the control axis: Pitch, Roll, and Yaw. The Auto-Stabilisation system generated signals in Pitch Roll and Yaw as a function of aircraft rate of movement and Mach number from the Air Data Computer.


The Artificial Feel system comprised of two separate channels for each control axis, Pitch, Roll and Yaw. Artificial feel is provided on each control axis. Pitch, Roll and Yaw, by a spring rod that increased the control stiffness with increasing control deflection, supplemented by dual control jacks that change the stiffness as a function of speed at speeds above approach speed.

Conventional trim was provided in Roll, Yaw and Pitch. The trim cancelled the load of the Artificial Feel by changing the feel datum, and consequently the neutral position of the flight controls.

An electric trim system was provided only in Pitch, and comprised two separate but identical channels. The electric trim could be controlled either directly by the pilot using the Pitch Trim selector on each control column or independently of the pilot in auto trim when either autopilot was engaged or for automatic pitch stability correction. As part of the Trim system Concorde had Automatic Pitch Stability Correction.

Concorde had an Anti-Stall system which operated (when engaged) at speeds below 270 knots from about 10 seconds after lift-off. At high angle of attack conditions the anti-stall system augmented the basic pitch Auto-Stabilisation with a Super Stabilisation function, and created an unmistakable warning at the approach to very high angles of attack through the Artificial Feel and a Stick Shaker.


Finally there was an Emergency Flight Control System which provided an additional flight control capability in Pitch and Roll axes in the event of a control jam between the control column and the Relay Jacks.

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