Operating in a degraded visual environment (DVE) poses a significant risk to helicopter operations. A DVE can be caused by partial or total loss of visibility from airborne dust, sand, or snow stirred up by the helicopter’s rotor downwash. A DVE can cause a loss of spatial orientation and situational awareness, which has on several occasions led to controlled flight into terrain, ground obstacle collisions, and the loss of aircraft and personnel. DVEs have driven the development of new display technologies, which in turn present new challenges, including the integration of scene imagery, visual symbology, tactile cueing, and aural cueing. In a full-motion DVE simulation study with seven test pilots, we evaluated aural and tactile cueing along with sensor imagery displayed on either a helmet-mounted display (HMD) or panel-mounted display (PMD). The symbology and forward looking infrared (FLIR) imagery were presented on a UH-60M PMD or a SA Photonics high definition, wide field-of-view, binocular HMD. Additionally, the synergistic effects of aural and tactile cues were assessed. Tactile cues were presented via belt, shoulder harness, and seat cushion using electromechanical tactile stimulators. Aural cues were presented via an HGU-56/P rotary-wing aircrew helmet. The compatibility and effectiveness of each combination of FLIR sensor imagery, selected display, and aural and tactile cueing set were evaluated with quantitative measures of flight performance, pilot subjective reports, and pilot psychophysiological measures.
Color is one of the latest design characteristics of helmet-mounted displays (HMDs). It’s inclusion in design specifications is based on two suppositions: 1) color provides an additional method of encoding information, and 2) color provides a more realistic, and hence more intuitive, presentation of information, especially pilotage imagery. To some degree, these two perceived advantages have been validated with head-down panel-mounted displays, although not without a few problems associated with visual physiology and perception. These problems become more prevalent when the user population expands beyond military aviators to a general user population, of which a significant portion may have color vision deficiencies. When color is implemented in HMDs, which are eyes-out, see-through displays, visual perception issues become an increased concern. A major confound with HMDs is their inherent see-through (transparent) property. The result is color in the displayed image combines with color from the outside (or in-cockpit) world, possibly producing a false perception of either or both images. While human-factors derived guidelines based on trial and error have been developed, color HMD systems still place more emphasis on colorimetric than perceptual standards. This paper identifies the luminance and color contrast requirements for see-through HMDs. Also included is a discussion of ambient scene metrics and the choice of symbology color.
Project Manager (PM) Apache Block III contacted the U.S. Army Aeromedical Research Laboratory (USAARL), Fort Rucker, Alabama, requesting assistance to evaluate and find solutions to a government-developed Helmet Display Unit (HDU) device called the Mock HDU for helmet alignment of the Apache Advanced Integrated Helmet (AAIH). The AAIH is a modified Head Gear Unit No. 56 for Personnel (HGU-56/P) to replace the current Integrated Helmet and Sighting System (IHADSS). The current flashlight-based HDU simulator for helmet/HDU alignment was no longer in production or available. Proper helmet/HDU alignment is critical to position the right eye in the small HDU eye box to obtain image alignment and full field of view (FOV). The initial approach of the PM to developing a helmet/HDU fitting device (Mock HDU) was to duplicate the optical characteristics of the current tactical HDU using less complex optics. However, the results produced questionable alignment, FOV, and distortion issues, with cost and development time overruns. After evaluating the Mock HDU, USAARL proposed a cost effective, less complex optical design called the Helmet/HDU Alignment Tool (HAT). This paper will show the development, components, and evaluations of the HAT compared to the current flashlight HDU simulator device. The laboratory evaluations included FOV measurements and alignment accuracies compared to tactical HDUs. The Apache helmet fitter technicians and Apache pilots compared the HAT to the current flashlight based HDU and ranked the HAT superior.