This SAE Aerospace Recommended Practice (ARP) describes the recommended performance levels for equipment located on the aircraft exterior which produces radiant energy which will provide desired information when viewed with NVIS goggles.
These performance intensities, normally stated in candelas for visible light, are modified to consider the goggle spectral response range. Where necessary, location of the equipment on the airplane is specified.
The spectral emission characteristics may or may not include visible light. Whether or not visible energy is emitted, this document will refer to these items of equipment as "lights".