This document defines a Head-Up Display (HUD) system intended for installation in all types of aircraft. It describes the physical form factors, fit dimensions, electrical interface definition and typical HUD functions, including the display of navigation and guidance information in the flight crew's forward field of view. The HUD accomplishes this by projecting images onto a combiner with symbology that conforms to the outside world view. Guidance for HUD architectures include single, twin, dual and HUD integrated with Primary Flight Display (PFD). This document is an practical guide for the design of federated equipment and integrated modular avionics.