This SAE Aerospace Recommended Practice (ARP) covers the general requirements and test procedures for illuminating systems for integrally lighted aircraft instruments in order to provide (a) uniformity of illumination within each instrument@ (b) legibility of instrument presentation under daylight or integral light@ and (c) uniformity of illumination between instrument displays. Purpose: The purpose of this document is to recommend certain basic considerations and criteria which the designer should observe when designing a system of red integral lighting for aircraft instruments.?