This SAE Aerospace Recommended Practice (ARP) covers the general requirements and test procedures recommended for use with white incandescent integrally lighted instruments. Its use should provide uniformity of illumination from instrument to instrument and legibility under daylight operation. An appendix is provided to familiarize the designer with some of the techniques used to obtain uniformity of color and illumination in various types of instruments. Purpose The purpose of this document is to recommend to the designer the various criteria and to familiarize him with techniques associated with white incandescent lighted aerospace instruments.