Can take up to 25 seconds says the book, but in practice i dont think i've ever had to wait more than about 10 -15. Usually about 5 or so. Whats off putting is when it catches you halfway through the change eg, drop from 220 to 130, and SFL promptly changes to (say) 120.... Usually its correct at the next refresh, or you get a call obviously! More often than not, if it does pick it up as you are changing it it'll say something blatantly wrong that doesnt end in a zero.
And if you fly a saab with a dodgy txpdr, we know to ignore the sfl!
