Friday, 9 November 2012

HELMET-MOUNTED DISPLAY ("H-MOUNT-D")



HELMET-MOUNTED DISPLAY (H-MOUNT-D - PRONOUNCED "H-MOUNT-D") is a device used in some modern aircraft, especially combat aircraft. HMDs project information similar to that of head-up displays (HUD) on an aircrew’s visor or reticle, thereby allowing him to obtain situational awareness and/or cue weapons systems to the direction his head is pointing. Applications which allow cuing of weapon systems are referred to as helmet-mounted sight and display (HMSD) or helmet-mounted sights (HMS).





IMPORTANT ASPECTS
While conceptually simple, implementation of aircraft HMDs is quite complex. There are many variables
§  PRECISION - the angular error between the line-of-sight and the derived cue. The position of the helmet is what is used to point the missile; it thus must be calibrated and fit securely on the pilot's head.
§  The line between the pilot's eye and the RETICLE on the visor is known as the LINE OF SIGHT(LOS) between the aircraft and the intended target. The user's eye must stay aligned with the sight – in other words, current HMDs cannot sense where the eye is looking, but can place a "PIPPER" between the eye and the target.
§  LATENCY OR SLEW RATE - how much lag there is between the helmet and the cue.
§  FIELD OF REGARD - the angular range over which the sight can still produce a suitably accurate measurement.
§  WEIGHT AND BALANCE - total helmet weight and its Center Of Gravity, which are particularly important under high "g" maneuvers. Weight is the largest problem faced by fighter aircraft HMD designers. This is much less a concern for helicopter applications, making elaborate helicopter HMDs common.
§  Safety and cockpit compatibility, including Ejection Seat compatibility.
§  Optical characteristics LIKE eye dominance.
§  DURABILITY and ABILITY to handle day to day wear and tear.
§  Cost, Including Integration And Training.