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Concorde Autothrottle Actuator

Technical Information

Catalogue No: C0317
Category: Engine Control
Object Type: Actuator
Object Name: Concorde Autothrottle Actuator
Part No: (Rotax) CU0101
Serial No: 04
Manufacturer: Rotax
Division: Flight Controls [FCD]
Platform(s): Concorde
Year of Manufacture: 1966
Dimensions:
Width (mm):
285 
Height (mm):
195 
Depth (mm):
235 
Weight (g):
9,700 
Location: Rack RAA02 [Main Store]
Inscription(s):

Elliott SFENA
Consortium Design
Unit: Autothrottle Actuator
Type: 60-005-01
Ser. No. 04
Code: 66 266 245 00
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Mods: Incorporated -
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Autothrottle Actuator
Type (Rotax) CU.0101
Serial No. (Rotax) 04
Manufactured for Elliott Bros Ltd by
Rotax Ltd. London, England.
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Not For Flight
N0n Autorise de Vol

Notes:

The Autothrottle Actuator is an electro-mechanical unit which operates the pilot’s throttle levers in response to electrical thrust demand signals from the Autothrottle Computers. The unit houses two segregated servo systems each being connected to the final output via channel isolation clutches. The final drive mechanism incorporates a separate output isolation clutch, a final reduction gear, a slip clutch and position feedback sensors for each throttle lever.

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.

An autothrottle (automatic throttle, also known as autothrust, A/T) is a system that allows a pilot to control the power setting of an aircraft's engines by specifying a desired flight characteristic, rather than manually controlling the fuel flow. The autothrottle can greatly reduce the pilots' workload and help conserve fuel and extend engine life by metering the precise amount of fuel required to attain a specific target indicated air speed, or the assigned power for different phases of flight. Autothrottle and AFDS (Auto Flight Director Systems) can work together to fulfill the whole flight plan.

There are two parameters that an Autothrottle can maintain or try to attain: speed and thrust.

In speed mode the throttle is positioned to attain a set target speed. This mode controls aircraft speed within safe operating margins. For example, if the pilot selects a target speed which is slower than stall speed, or a speed faster than maximum speed, the autothrottle system will maintain a speed closest to the target speed that is within the range of safe speeds.

In the thrust mode the engine is maintained at a fixed power setting according to the different flight phases. For example, during takeoff, the Autothrottle maintains constant takeoff power until takeoff mode is finished. During climb, the Autothrottle maintains constant climb power; in descent, the A/T reduces the setting to the idle position, and so on. When the Autothrottle is working in thrust mode, speed is controlled by pitch (or the control column), and not by the Autothrottle. A radar altimeter feeds data to the Autothrottle mostly in this mode.

Linear Actuators: On aircraft linear actuators may be used for flight control surfaces, wing flaps, and spoilers. Hydraulics deliver a great deal of power without taking up too much space or weight, meant that they massively help pilots in undertaking necessary mechanical tasks without using too much energy.

The other advantages of hydraulics are the quick response to the demands that may be placed upon the system. They are also reliable and reasonably easy to maintain. Because they do not use electricity, there is no chance of a shock hazard, and the chances of being a fire hazard are low, which makes them a safer option than other equivalent systems.

Perhaps the main advantage of a hydraulic system is that they can handle a practically unlimited amount of work due to the immense force they can produce. This is all the more important in modern day aircraft.

Hydraulic fluid is pumped from a reservoir, either by an electric, or engine driven pump. It is filtered to keep it clean, and then passes through a selector valve, which relieves extra pressure.

Once it reaches the linear actuator, the fluid power is turned into work by a piston. This power is then used to move an aircraft system or flight control. These actuators can be either single or double acting, depending on the requirements of the system, meaning that the fluid can be applied to one or both sides of the actuator. The selector valve allows for the fluid direction to be controlled, which is necessary for operations such requiring extension and retraction.

The actuating cylinder also contains a reduction gear, which allows it to control the rotating motion to what is needed within the system. Previously, systems would use steel cables connected by pulleys to control motion. The cables that connected the controlling mechanism, such as the pedals, to the controlled surface, such as the rudder, would be subject to expansion due to temperature changes. Hydraulic systems though, are capable of controlling motion without worrying about such concerns, as they do not operate in an environment that is not open to the atmosphere. This means that hydraulic systems not only provide better control for the pilots using them, but also increase response times, making them an imperative part of aerospace engineering.

http://www.acorn-ind.co.uk/insight/The-role-of-hydraulic-actuators-within-aircraft-systems/

Rotary Actuators:

Electric rotary actuators:

Stepper motors are a form of electric motor that has the ability to move in discrete steps of a fixed size. This can be used either to produce continuous rotation at a controlled speed or to move by a controlled angular amount. If the stepper is combined with either a position encoder or at least a single datum sensor at the zero position, it is possible to move the motor to any angular position and so to act as a rotary actuator.

Servomotors

A servomotor is a packaged combination of several components: a motor (usually electric, although fluid power motors may also be used), a gear train to reduce the many rotations of the motor to a higher torque rotation, a position encoder that identifies the position of the output shaft and an inbuilt control system. The input control signal to the servo indicates the desired output position. Any difference between the position commanded and the position of the encoder gives rise to an error signal that causes the motor and geartrain to rotate until the encoder reflects a position matching that commanded.

Fluid power rotary actuators:

Hydraulic power may be used to drive an actuator, usually the larger and more powerful types. Fluid power actuators are of two common forms: those where a linear piston and cylinder mechanism is geared to produce rotation (rack and pinion), and those where a rotating asymmetrical vane swings through a cylinder of two different radii. The differential pressure between the two sides of the vane gives rise to an unbalanced force and thus a torque on the output shaft. Vane actuators require a number of sliding seals and the joints between these seals have tended to cause more problems with leakage than for the piston and cylinder type. The three most commonly used types are, vane and helical.

Simple planetary actuators are most commonly used for commercial leading edge slat applications while compound differential planetary actuators offer higher ratios for torque multiplication and are most commonly used for trailing edge flap designs.

 

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