What did PPI contribute to Royal Navy night operations?
Short answerPPI let ships track friendly units as well as targets, allowing formations such as line abreast without showing lights.
NotesA plan-position indicator did more than find the enemy: it showed friendly ships well enough to hold station in darkness. That made line-abreast formations practical where earlier night operations often required line ahead to preserve visual contact. A dispersed line could search or attack across a wider front without revealing itself with formation lights. The effect was especially important for later Royal Navy night-fighting tactics.