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Hydraulic Actuator Demonstrator

Technical Information

Catalogue No: C0310
Category: Flight Control
Object Type: Actuator
Object Name: Hydraulic Actuator Demonstrator
Part No: 48419H1 Iss 24
Serial No: FYH111538
Manufacturer: Unknown
Division: Unknown
Platform(s): Tornado
Year of Manufacture: Unknown
Dimensions: Width (mm): 303
Height (mm): 355
Depth (mm): 315
Weight (g): 16,460
Location: Rack RAA02 [Main Store]

Part No. 48419H1 Iss 24
Serial No. FYH111538


This later unit is probably another prototype unit. and is fitted with a 700mm cable

It was in 1950 that Elliott Bros. set up a small team to try to break into aircraft automation, In 1958 work was started at Borehamwood on a new automatic flight control system for the English Electric TSR 2, a high performance aircraft for use both for strike and reconnaissance purposes. The complete system of automatic control equipment, hydraulic power controls, simulated control surface forces, and simulated characteristics was assembled at Rochester.

The Quadruplex Actuator comprises four separately controlled electrohydraulic actuators which are individually coupled to a common output member by clutch plates rotating around the common output shaft. The Actuator is normally utilised as a position servo, separate and isolated servo-amplifiers being used for each of the four lanes to sum the position demand input and the position feedback and provide a drive for the electrohydraulic valve of each lane. The operating pressure is 3000lbf/in2

A working demonstrator built in perspex and opearted from a pneumatic air supply to illustrate the basic concept was shown at the SBAC Exhibition at Farnborough in 1963. A Quadruplex Actuator was first supplied in linear form in 1964 for the FIAT G95 VTOL rig followed by a similar set for the Dornier DO31 simulator rig. The lightweight rotary form was developed under a Ministry of Technology contract for a Failure Survival Autostabilization System.

In 1970 the company won the prime contract for development of the Command Stability Augmentation System (CSAS) and Autopilot/Flight Direction System (AFDS) for Tornado. The design of the Tornado Quadruplex Actuator was that of Stafford Ellis the most prolific inventor in this company’s history. Tornado has an advanced “fly-by-wire” control system. This entails electrically signaling the commands from the pilot’s control column to the aircraft’s flying controls and solves the problems which are associated with mechanical control systems on aircraft with advanced performance and variable wing-sweep angles. Electrical signaling also enables the control response to be supplemented electronically, so compensating for the wide variations in aircraft characteristics over its wide flight envelope.

The flying controls for Tornado comprise tailerons, rudder and spoilers and the control surface movements required in manoeuvring and stabilising the aircraft are electronically computed and electrically signalled to the power control servo units which position the taileron, rudder and spoiler control surfaces.

The taileron and rudder power control servos each embody a quadruplex electrohydraulic actuator which converts the electrically-signaled control surface demands into mechanical movements and enables the system to survive failures to an extent compatible with the electronic computing and main hydraulic power control elements in the system. Fairey Hydraulics developed the Tornado actuator under licence from Marconi Elliott Avionics and adapted the hydraulic design to suit the specific requirements of the Tornado. The quadruplex actuator was developed as an integral part of the taileron and rudder power control units which Fairey Hydraulics supplies. The Quadruplex Actuator was fitted to all variants of the Tornado.       

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.


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.


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.


The Tornado originally came in two variants; the Interdictor Strike Version (IDS) for the German, Air Force and Navy, Italian Air Force, and the Royal Air Force, and the Air Defence Variant (ADV) for the Royal Air Force only. Marconi-Elliott Avionic Systems provided a wide range of equipment for both variants.

• Digital Autopilot Flight Director System (AFDS)in conjunction with Aeritalia, Italy
• Command Stability Augmentation System (CSAS)  in conjunction with Bodenseewerk, Germany
• Quadruplex Actuator Integrated into Fairey Hydraulics power control unit
• Stores Management System (SMS) in conjunction with Selenia, Italy
• Fuel Flowmeter System in conjunction with Teldix, Germany and OMI, Italy
• TV Tabular Display System in conjunction with AEG Telefunken, Germany
• Combined Radar and Projected Map Display (CRPMD) from Ferranti
• E-Scope Display System
• Triplex Transducer Unit
• Central Suppression Unit
• Engine Control Unit

By 1980 the Enhanced E-Scope Display (EESD) was under development. This was was a digital design with a frame store, rather than the analogue design and long persistence phosphor CRT of the original E-Scope Display (ESD). The EESD part number was 79-061-xx and this version was probably fitted to the majority of Tornado IDS aircraft.

RAF IDS variants were initially designated the Tornado GR1 with two variants called the Tornado GR1A and Tornado GR1B; the Tornado F3 was yet another version.

The contract covering the development and production investment for the Royal Air Force's mid-life update (MLU) for their 229 Tornado GRl and F3 aircraft was signed in April 1989. The upgrade included the following:

• Introduction of a new avionics architecture built around a 1553 databus.
• New sensors & Displays consisting of a Forward Looking Infra-red sensor, a Pilot's Multi-Function Display with digital map, wide angle HUD, Computer Symbol Generator, Video recording System and a Computer loading System.
• New Armament Control System consisting of a Stores Management System, a Weapon Interface Unit linked to a 1553 databus within a 1760 interface.
• A Night Vision Goggle compatible cockpit and the aircraft is also equipped with Forward Looking InfraRed (FLIR)
• Terrain Reference Navigation /Terrain Following Display/Terrain Following Switching & Logic Unit /Covert RadAlt.

Ferranti won the contract for the new HUD, Active Matrix Liquid Crystal Displays (AMLCD) to replace the TV Tabs, EHDD and E-scope. To support the new avionics a new Computer Signal Generator (CSG), with several times the computing capacity of the original Tornado main computer, and using the new high level ADA progamming language was procured

The Ferranti Nite-Op jettisonable NVGs were also procured under a separate contract.

In the event the MLU project stalled. In March 1993 a new Mid-Life Upgrade (MLU) project was launched and in1994 the UK signed a contract for MLU of GR1/GR1A/GR1Bs to GR4/GR4A standard.

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