A dangerous situation is created when the pilot looks inside the cockpit for instrument information when flying combat and low altitude missions. While looking at instruments, a pilot cannot be performing situation analysis; yet not looking at instruments runs such risks as flying into the ground, particularly in low visibility conditions or in relatively featureless terrain where visual cues for altitude and attitude are inadequate or deceptive. The AN/AVS-7 HMD solves this problem for night flight for both helicopters and fixed wing aircraft which must operate in a 'nap of the earth' flight regime. The display unit mounts on the AN/AVS-6 night vision goggles and provides symbology overlaid on the pilot's outside view; cockpit instrument information is thus provided through the goggles. The pilot is immediately aware of changes in either his surroundings or the instrument readings. This minimizes the risk of critical information being missed in one area while the pilot is looking in the other. The 'day' HMD version of the AN/AVS-7 display now carries these advantages into daytime flights. This display unit operates in conditions from full sunlight to dusk, provides the same symbology as the night display, and connects to the night display interface with no aircraft modification. The day HMD mounts to the helmet using the attachment points previously reserved for the night vision goggles. This display improves the safety of daytime operations by keeping the eyes 'out of the cockpit' in difficult situations such as those presented during landings, cargo lifting and flight utilizing terrain masking. It offers the possibility of a less stressful way of familiarizing the pilot with the symbology and of the dynamic relationships it has to the aircraft and background motions. This familiarization is now accomplished during night flights using night vision goggles. The 'day' HMD is also a useful maintenance aid, easing the ground crew's checkout of the aircraft systems during the day.