External Position Lighting Effects on Night Vision Goggle Performance.
ARMY AEROMEDICAL RESEARCH LAB FORT RUCKER AL
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Army aviation depends heavily on image intensification Iexp 2 devices to extend operations into the night. Such devices are light amplification systems that adjust their amplification factor gain according to the level of ambient illumination. However, these night vision goggles NVGs are unable to distinguish between light originating from the exterior scene and light originating from either instruments inside the cockpit or lights mounted to the aircraft. Consequently, the NVG may lower gain unnecessarily, and in doing so, degrade image quality. The compatibility problem is most apparent when light in the red part of the spectrum is present. This is the problem with the UH-1s red lateral position lights. These lights flood into the cockpit, affecting NVG performance - the presence of fog and other weather heightens this effect. A solution to this problem has been to mask appropriate upper and lower portions of the two red position lights, thereby reducing the NVG degradation. However, this solution appeared to conflict with Federal Aviation Regulation FAR lighting intensity distributions for each of the two lights. We calculated that the FAR could be satisfied at a distance of one rotor disk radius by masking 82 degrees of each respective position light leaving 98 degrees unmasked. Objective video recordings and test pilots subjective observations indicate a significant reduction in NVG degradation with the 82-degree masking scheme as compared to operations with unmasked position lights. The 82-degree masking scheme meets the FAR requirements while reducing simultaneously the performance degradation of the NVG devices.
- Optical Detection and Detectors
- Protective Equipment