|Rochester Photo Negative
|Concorde Pitch Relay Jack Sensor
|13 Jun 1967
|Negatives Cabinet PM ("54/" Negs) [RAA Office]
The position transmitters on the flying control hydraulic booster jack are known as ‘Relais’ jack sensors. These produce two-wire synchro information on stick position for the autostabiliser and autopilot. There is a separate unit for each axis of flying control movement i.e. pitch, roll and yaw.
Each unit carries the necessary synchros for channels 1 and 2and command and monitor computing. The units therefore incorporate design techniques aimed at minimising the common failure probability. The units are mounted on the auxiliary hydraulic servo unit earth point and auxiliary servo extension is transmitted via a trailing link to the sensor input arm.
Each Relay Jack is a twin-ram, electro-hydraulic actuator. Each ram's displacement in speed and
direction is controlled by a spool valve. Each spool valve is monitored for jamming by a detector,
linked to the BLUE jam light (if the corresponding ram is supplied by the Blue hydraulic system), or the GREEN jam light (if the ram is supplied by the Green hydraulic system).
The detection of a jammed condition automatically signals the relevant Relay Jack hydraulic
selector to shut, thus removing hydraulic power (normal or standby) from the jammed side of the
relay jack. This automatic shut-off ensures that a flight control axis cannot be frozen by this single
Each Relay Jack is also used as an Auto-Pilot input point.
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 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.