Tornado CSAS Roll/Yaw Position Transmitter

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
• TACAN
• 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.