Projected Map Display [PMD]

In 1967 Elliotts had been awarded a major contract for the design, development and integration of a Navigation and Weapon Aiming Sub-System (NAVWASS) for the RAF's new Jaguar aircraft.

The Jaguar was designed as a close air support aircraft for supporting ground troops in daylight. The NAVWASS enabled the pilot to navigate and fly at low level and high speed to acquire and accurately attack targets. Trials of the prototype Jaguar system were carried out using a Varsity aircraft at West Malling airfield in Kent

The Jaguar NAV/WASS  sub-system comprises four principal groups of equipment. The sensors, which measure what the aircraft is doing and feed these measurements into the computer; the computer sub-system which processes this measured information into a form which can be used by the pilot; the cockpit controls which control the system's mode of operation and lastly, the cockpit displays which show to the pilot the computer's outputs of converted measurement information and also information, such as target or waypoint position, which is being input into the computer. The system included an E3R inertial platform, Digital Computer, a HUD, Projected Map Display, Horizontal Situation Indicator and various cockpit control panels.

This Projected Map system predates the modern digital systems and uses 35mm film as the data store. The film is stored on spools mounted in a moveable carriage. A tungsten halogen lamp provides the light source to project the map image via an optical system on to a ground glass screen. A fresnel lens covering the screen gives even illumination and intensifies the image in the pilot’s field of view. The film strip is driven between the two spools at a rate proportional to the Easterly ground speed while the carriage holding the spools is driven in a perpendicular direction proportional to the Northerly ground speed. The map can be presented as North or Track oriented. The screen can be rotated and has a track arrow. The aircraft’s present position, track and track to the next waypoint can be presented. A film can cover an area of about 750 by 750 nautical miles with a Scale change for 1:250 000 or 1: 500 000. The PMD was used in the Jaguar Navigation and Weapon Aiming Sub-System NAVWASS. The Marconi Avionics system was replaced with TIALD from 1995