|Object Type:||Display Unit|
|Object Name:||Projected Map Display [PMD]|
|Year of Manufacture:||circa 1970|
|Location:||Main Object Store|
Projected Map Display
Type No 79-008-01
Ref No 6JA/111-8583
Ser No 103
Code No K0656
The unit has a second visible label on one of its modules that reads:
"Chassis Wired Assy
Type No 75D23070
Ref No 6JA/6259991
Serial No 103
Code No K0656"
And is also marked in white ink with:
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.
This Projected Map Display unit, Serial No. 103 has 403 flight hours recorded. It was made by Elliott’s and the product is referenced in Company brochures as early as 1970.