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Triplex Transducer Unit

Technical Information

Catalogue No: C0562
Category: Air Data
Object Type: Sensor/Transducer
Object Name: Triplex Transducer Unit
Part No: 50-061-01
Serial No: 0005
Manufacturer: Marconi-Elliott Avionic Systems Ltd
Division: Instrument Systems [ISD]
Platform(s): Tornado
Year of Manufacture: circa 1975
Dimensions: Width (mm): 93
Height (mm): 169
Depth (mm): 396
Weight (g): 5,900
Location: Rack RAA10 [Main Store]

Marconi-Elliott Avionics
Triplex Transducer Unit
Part 50-061-01
Ser 0005
Code K0656
[inspection stamp]


The Triplex Transducer Unit (TTU) generates high integrity triplex analogue air data information for use by the MRCA Command and Stability Augmentation System (CSAS), and duo-duplex analogue outputs of static pressure for use by the Main Engine Control Unit (MECU). A secondary function is to provide duo-duplex discrete outputs of Mach number to the MECU and a number of simplex discrete outputs to the aircraft's configuration warning lamps, ejector valve relay, airbrake retraction relay and undercarriage warning lamp.

The unit comprises three identical dual pressure transducers, each containing a static and pitot-static assembly which outputs signals representing linear static pressure and linear pilot-static pressure. Each transducer is fully temperature compensated and consists of a pressure sensitive diaphragm driving the wiper arm of a plastic film potentiometer. The simple and well established working principles of the unit give the high integrity required, whilst the packaging of a pair of transducers into a space less than that usually used for a single unit, enables the TTU to be housed in a very small package.

The use of optical isolator links in the analogue electronics, and the duplication of electronic cards achieve the necessary degree of electrical isolation for the three CSAS channels, and the two MECU channels. The electronics involve conventional integrated circuits and discrete components mounted in twelve modules, which plug into a multi-layer motherboard (which replaces the conventional bulky wiring harness).

The TTU receives pitot pressures from the compensated nose probe and two side mounted probes, and static pressures from the three tappings on the compensated static wedge.

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.

The primary flight controls of the Tornado are a fly-by-wire hybrid, consisting of an analogue  Command and Stability Augmentation System (CSAS) connected to a digital Autopilot & Flight Director System (AFDS); in addition a level of mechanical reversion capacity was retained to safeguard against potential failure. To enhance pilot awareness, artificial feel was built into the flight controls, such as the centrally located stick; because of the Tornado's variable wings enabling the aircraft to drastically alter its flight envelope, the artificial responses adjust automatically to wing profile changes and other changes to flight attitude. As a large variety of munitions and stores can be outfitted, the resulting changes to the aircraft's flight dynamics are routinely compensated for by the flight stability system.

The Command Stability Augmentation System (CSAS) is by its very nature one of the most complex systems on Tornado. Hardly detectable in the cockpit, the CSAS keeps the ride comfortable at all speeds and altitudes, and makes the aircraft controllable throughout the flight envelope. It is a "fly-by-wire" system with autostabilisation, the pilot’s control demands being signalled and augmented electrically to maintain good handling qualities over the wide flight envelope. In the pitch axis, the "fly-by-wire" system has mechanical reversion.

The system is triplicated and includes triplex computing, triplex rate gyros, triplex position sensors and a triplex accelerometer, with quadruplex outputs driving quadruplex electrohydraulic actuators. These "fly-by-wire" actuators were originally designed by Marconi-Elliott Avionic Systems Limited and have now been integrated by Fairey Hydraulic into the aircraft’s main hydraulic power control units.

The CSAS electronics is packaged in two units, the pitch computing circuitry being housed in a single computer and the roll, yaw and spoiler circuitry in a similar computer.

The system uses very high-precision analogue circuitry to provide accurately- matched control lanes, and a unique voter monitor design which reduces transient effects, due to system failures, to a low level and is so designed also that nuisance warnings are rare.

Marconi-Elliott Avionic Systems Limited has design leadership on the CSAS programme, but shared the production with Bodenseewerk Geratetechnik.

The system was designed to Specification SP-P-41600.

The Command Stability Augmentation System comprises the following line replaceable units,

1 Rudder pedal position transmitter              Between front rudder pedals.
2 CSAS Power Distribution Unit                     Right hand forward avionic compartment.
3 CSAS Control Unit                                       Front Cockpit - left hand console.
4 Pitch Computer                                           Right hand rear avionic compartment.
5 Lateral Computer                                        Right hand rear avionic compartment.
6 Roll Position Transmitter                             Zone 19. Roll crate.
7 Pitch Position Transmitter                           Zone 19. Pitch crate.
8 Yaw Rate Gyro                                            Zone 22. Right hand under-carriage bay.
9 Roll Rate Gyro                                            Zone 21. Left hand under-carriage bay.
10 Pitch Rate Gyro                                        Zone 21. Left hand under-carriage bay.


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