Hi Captain_BH,
I'm not that smart - but in the example they give, it shows how to estimate the N1 Flex is about 85 and a bit %. (50C Flex, P Alt 2,000 ft and OAT = -10C)
If you look in the top right hand corner (Corner Point), they have drawn a graph showing flat rating temp v P ALT curve. At a Pressure Alt of 2,000 ft, the curve is intercepted at 40 degs C.
In this particular example, since the OAT < than the "Corner Point" value (Flat rating Temperature) then no correction is required.
