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Helmet Mounted Sight

Technical Information

Catalogue No: C0386
Category: Head-Mounted Equipment [HMD/NVG/Glasses]
Object Type: Display Unit
Object Name: Helmet Mounted Sight
Part No: ?
Serial No: ?
Manufacturer: Helmets
Division: Unknown
Platform(s): T-38 Talon
Year of Manufacture: circa 1978
Dimensions: Width (mm): 276
Height (mm): 230
Depth (mm): 290
Weight (g): 1,604
Location: Rack RAA15 (HMDs) [Mezzanine Store]

Helmets Limited


The Helmet Mounted Sight allows information to be over-laid onto the pilot’s line of sight wherever he may be looking. In this design a collimated image of an LED matrix display is projected off the inner surface of the visor into the pilot’s right eye.
The LED Matrix is a 32x32 element transmitting at 640nm (red). The optics uses a single prism and provides focussing and collimation. The optics projects onto a dichroic patch deposited on the inside of the polycarbonate visor. A dark, 15% transmission visor is also fitted to the Helmet. Other key features are a 10degree field of view, 16mm exit pupil, Autobrilliance and a 500Hz refresh of the display. The accuracy of the display system is 2mRad at the centre and 4mRads at the edge.
The Helmet Mounted system is built onto a standard Mk IV Alpha Helmet. A Head position system is also used to identify the angle at which the pilots head is pointing such that the appropriate symbology for overlay on the outside world can be presented.
A space model was windblast tested particularly to validate the novel visor latch mechanism and the Helmet survived a 450knot blast on the first run.
The second HMD was delivered in 1979 and three more in 1980 together with a Matrix Symbol Generator.
One of these HMD was supplied to the US Navy Pacific Missile Test Center and used in a successful trial in a T38 run jointly by the USAF and USN at Randolph AFB Texas. The trial concentrated on the benefits of energy management symbology.
This HMD has a small mains powered driver unit on the end of the umbilical cable which allows it to be used for demonstrations and it has been to many exhibitions and schools.
The given size is for just the helmet; the given weight is for the helmet and its 0.5m comms and 2m display cables.
The driver unit's size is 79 x 79 x 167 mm, plus a 1.8m mains cable; the driver unit plus its mains cable weighs 1219g.

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