Well thank you sir, that has worked (to an extent)!
Had no idea the real bug was Asobo assumed every monitor runs at 60FPS 
whats that a 10 minute bug fix to add “divide by monitor refresh rate” but ignored for 14months while they chase the xbox release date bonus money?
My fan still blows but its quieter as its now only trying to hit 60fps so much appreciated!
While you are here you got any clever tricks to solve the 2 mouse panning bugs that totally wreck the cockpit viewpoint experience? [BUG LOGGED] Freelook with mouse causes controls to freeze after SU5 - Bugs & Issues / Miscellaneous - Microsoft Flight Simulator Forums and the new SU7 one Whats wrong with the mouse inside the cockpit? - Bugs & Issues / Miscellaneous - Microsoft Flight Simulator Forums