High Quality Content by WIKIPEDIA articles! A helmet mounted display (HMD) 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).