Guys,
Maybe he was asking about ground use of TAI?
Flying turboprops many years back,the aircraft was fitted with a TAT kinetic heating chart.
Basically at 250 kts,a TAT of 10c would give SAT of O degrees C.
Also on the ground,there is a drop of temperature as ambient air is sucked into the engine,i believe there was a discussion whether +5 c would be a more sensible restriction as the drop in temp was around 3c.,but no news.
The same for the WAI,should be used for example at less than 10c in visible moisture.(vis 1500m or less,rain..).
In any case,follow your aircraft AFM guidance.