|Triplex Transducer Unit
|Marconi-Elliott Avionic Systems Ltd
|Instrument Systems [ISD]
|Year of Manufacture:
Width (mm): 93
Height (mm): 169
Depth (mm): 396
Weight (g): 5,900
|Rack RAA10 [Main Store]
Triplex Transducer Unit
EBL ISD 22
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.