Requirements of an HMS/D for a night-flying helicopter

Helicopter pilots prefer for the night-flying tasks a combination of electro-optical sensors with different physical principles in the Infra-Red (IR) and in the near IR spectrum: Thermal Imager (TI or FLIR), Night Vision Goggles (NVG) or Low Light Level Television (LLLTV) . The limits of these three sensors are in extreme darkness with less than 1 mLux illumination or in heavy rain, fog or snow with temperature differences below 0.1 K or with cross-over effects respectively. The development goal for the near future should be an integrated, lightweight helmet h a binocular display on the visor providing two or three sensor images. The paper describes operational requirements, human engineering aspects and the requirements of an integrated light-weight helmet with two NVG-tubes and two CRTs to display superimposed NVG and TI images with flight symbologies.