Originally Posted by
Spitoon
In the past there was more guidance in the controllers' national instruction book (MATS Part 1) about what brilliance to select for which lights in specific visibilities but that is long gone.
Almost, but not quite. At Gatwick the lights are set up according to specified vis and/or cloud conditions, and while some variation is permitted in better vis ( pilot request or controller decision ) the lights must be set correctly when IRVRs show, or the IRVR value will be incorrect. Don't know about other airfields in this respect, but, when it's working properly, our lighting system also has presets which put all the required lights on at the " approved " setting when selected.