A single yellow triangle denoted embodiment of Radar Update 77-1 from 1978 onwards which conferred compatibility with Skyflash. Those aircraft without it could only be loaded with Sparrow. When the update was first introduced, it added a whole new level of considerations for engineers at the front line. The Phantom radar had several readily exchangeable Line Replaceable Units (LRUs). Some of these LRUs, once updated at 3rd/4th line, could only be used in the updated radars. For some LRUs, there were typically only 2 spares between 2 x squadrons. One spare had to be sent off-base for update - then there was only pre-update spare on base. When the updated spare returned, there was now only the updated spare on base as the pre-update one went away. Then when it returned, there were now 2 x updated ones and no pre-updated ones. This led to a lot of robbing between aircraft of both mod-states to maintain the overall 70% SACEUR readiness requirement each night. Occasionally, the only way to maintain the required readiness in RAFG, or to get the most out of a limited duration Missile Practice Camp at Valley, was to use an aircraft to ferry a U/S LRU in the nose and go and collect a serviceable LRU from a location that had one.
The additional yellow markings denoted later updates which added incremental improvements in capability such as snap-start on the Skyflash. I can't recall the other precise details.
Last edited by RAFEngO74to09; 2nd Nov 2013 at 20:53.