Helmet-Mounted Displays: - USAARL - The - U.S. Army

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Joseph R. Licina
and buckles, and survival vest and flotation equipment due to the low
mounting of the miniature CRTs.
In the past, attempts have been made to integrate and achieve
compatibility with protective masks and visual correction/protection. With
often different manufacturers for each component, this has been a
formidable task. A fairly recent example of the integration process is the
IHADSS helmet. The helmet was intended to be fitted while wearing the
M-43-A1 protective mask (designation changed to M-49 after 1996). When
the mask was not being worn, a custom skull cap was to have been used to
replicate the thickness and bulk of the protective mask. However, Apache
aviators are not using the skull caps, so the helmet doesn't fit properly when
the M-43 (M-49) mask is needed. The mask itself was designed to
minimize the adverse effects with the HMD.
The small bubble lenses of the M-43 mask were designed to fit very
close to the eyes to minimize eye clearances with the HMD. However,
since many IHADSS users can not obtain a full FOV even without the
mask, the addition of the mask further increases the distance between the
HDU and the eye, reducing the FOV. The close fitting eye lenses can fog
within a minute unless sufficient air is artificially circulated within the
mask. The over pressure and additional air is provided by a battery
powered blower when outside the aircraft and by aircraft power when
inside the aircraft. The batteries are lithium with no readily available
commercial equivalent, and have a duration of approximately 8 hours with
use.
To provide lens correction for distant vision, contact lenses are used for
Apache aviators since any corrective lens outsert would increase the eye
clearance and further reduce compatibility with the HDU. For presbyopic
Apache pilots, the bifocal contact lenses have not been approved. Also,
fitting one contact for near and the other for far vision has also not been
approved for Army aviation. The use of contact lenses by other than
Apache pilots has not been approved due to the lack of adequate logistics
and visual support (optometrists and ophthalmologists) to fit the lenses and
to follow-up with periodic examinations.
Under certain conditions, NVGs provide information the FLIR cannot.
Using only the FLIR, Apache pilots have difficulty in detecting other
aircraft at night with covert lighting that is only visible to NVGs. Also,
under any moon illumination, the ANVIS resolution is greater than the first
generation FLIR. Therefore, the gunner co-pilots (front seat) were