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Rate Gyro Unit

Technical Information

Catalogue No: C0570
Category: Gyro
Object Type: Sensor/Transducer
Object Name: Rate Gyro Unit
Part No: 11-018-01
Serial No: 003
Manufacturer: Honeywell
Division: Unknown
Platform(s): Tornado
Year of Manufacture: 1972
Width (mm):
Height (mm):
Depth (mm):
Weight (g):
Location: Rack RAA09 [Main Store]

Mfd by Honeywell GmbH
Rate Giro Unit - Pitch/Yaw
Type DGD414C1
P/N 11-018-01
Series No. AF2
Spec. No. SP-P-41600
Serial No. 003
Date 4972
Mod. Status ABC...NOP


A rate gyro is a type of gyroscope, which rather than indicating direction, indicates the rate of change of angle with time. The gyro has only one gimbal ring, with consequently only two planes of freedom and is used to measure the rate of angular movement. This unit has a Pitch and a Yaw Rate Gyro in the same package (they are frequently collocated near the wing root). Three such units form part of the CSAS.

This is an 'A' Model developed for MRCA, later Tornado.

A rate gyro is a type of gyroscope, which rather than indicating direction, indicates the rate of change of angle with time. The gyro has only one gimbal ring, with consequently only two planes of freedom and is used to measure the rate of angular movement.

In a rate indicating gyroscope, the gyroscope is turned at a steady rate about its input axis and a torque is applied to the spin axis. This causes the gyroscope to precess about the output axis. The rate indicating gyroscope consists of a damping fluid between the float assembly can and the outer casing. This viscous fluid resists the motion of the gimbal precession. This causes the gimbal to accelerate initially in the fluid, until the damping effect is equal to the precessing force. The rate of precession will hence be directly proportional to the rate of turn of the gyroscope about its input axis and the total angle of movement about the output axis will be proportional to the speed and length of time the input axis is turning.

In a typical application (e.g. an aircraft), the output axis could have revolved 180 degrees clockwise in 20 seconds, then 80° anti-clockwise (say if the aircraft was changing direction again). This output would then be fed to a computer to calculate the total distance traveled

Honeywell Licence

In April 1958 English Electric acquired a licence to manufacture Honeywell gyros at Stevenage. English Electric Aviation Ltd became a founding constituent of the British Aircraft Corporation (BAC) in 1960 and the guided weapons division was added to BAC in 1963. In 1975 BAC bought out the future royalties for the Honeywell license and BAC became part of the new BAE Systems in 1999.

The Miniature Rate Gyro (MIG) employs a gimbal floated at neutral buoyancy in a fluorocarbon fluid and pivoted between jewelled bearings. The manufacture and assembly of such a gyro called for standards of precision unprecedented not only in industry but even in specialist laboratories. A crucial issue was vibration. The Instrument Wing was located between the Eastern Region main line to the north and the new Stevenage by-pass road, and further vibration came from machinery in the company's plant—and even from the footfalls of the staff. Accordingly, test equipment was mounted on concrete plinths carried on 50-ton concrete rafts supported on air bellows resting on heavy foundations deep in the earth.

The assembly and test area were clean rooms fully temperature and humidity controlled and it is the only miniature inertial quality gyro in production in Europe. These Gyros were used in inertial guidance systems for missiles and torpedoes for example.

Northrop Licence

 Marconi licenced a range of gyros from Northrop; initially the GR-H4 in the mid-60's and then the G1-G6 in 1980.

The GR-H4 rate-gyroscope was built under licence from Northrop, producer of the original version. The gyro is contained in a 1in x 2 in cylinder and is extremely accurate and strong. It is fluid damped, but requires no heater controls. In 1968 Dick Scott and the Gyro Division team landed a major contract for Elliott Nortronics sub-miniature rate gyros for the television guidance head of the Anglo-French Martel air-to-surface missile; the ultimate value of the order iat that time was expected to exceed £900,000.

In 1980 Marconi Avionics of Rochester has just completed its 10,000th rate-gyroscope, marking 15 years of manufacture. The GR-H4 rate-gyroscope is built under licence from Northrop, producer of the original version. Applications of the Marconi Avionics-built gyroscope include the Sea Vixen carrier-borne interceptor guidance, the guidance system of Sky Flash, the RAF's most advanced air-to-air missile, and stabilisation of Harrier and the Sea Dart ship-to-air missile. While building GR-H4s, Marconi Avionics introduced several improvements, independently of Northrop. At the same time unit cost was reduced, by a factor of almost three. (The 1980 cost of the rate-gyroscope was £850-£l,300, depending on application.) Marconi Avionics improvements include replacement of the steel gyro casing with one of Monel nickel alloy incorporation of a mu-metal screen to isolate the gyroscope motor's magnetic field; introduction of chemical etching (in place of lapping) to trim the torsion bar; adaption of semi-automatic test equipment and multiple jigging to simplify production. Marconi Avionics also introducedplastic damping vanes and replaced hand-wired parts by flexi-circuits. In 1980 GR-H4 production rate was roughly 100 units a month.

In 1981 Marconi  introduced the GI-G6 into production in a £750,000 development. The G6 is proposed for the Spearfish torpedo (formally Naval Staff Target 7525), and a strapdown system using the gyro was fitted to the Machan experimental unmanned aircraft.

The input rate range is +/- 10deg/sec to +/- 1000 deg/sec.


Allied Signal  aquisition

Allied Signal was an American aerospace, automotive and engineering company created through the 1985 merger of Allied Corp. and Signal Companies. It acquired Bendix Corp. gyroscope business which was later sold to Condor Pacific Industries in 1999. Condor Pacific was established in 1964 to manufacture miniature mechanical, spinning wheel gyros. Condor later went on to acquire Allied Signal's gyro manufacturing business (1999) and shortly afterwards was itself acquired by BAE Systems (2002). BAE Systems acquires Condor Pacific and forms the BAE Systems Inertial Products Division.

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.


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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