flex temp
PJ2 & Wiley
refreshing to see there's a couple of sensible/intelligent contributors to this thread!
Keep up the good effort.
w.r.t. the FCOM, explanation:
whatever flex temp one enters can only be higher than the actual OAT. This is the adjustment/pilot input, to fool the Fadec into thinking it is a much hotter day/conditions than actual, therefore causing it to calculate reduced thrust settings primarily to protect against expected EGT limits or exceedances, & Secondly preserving unneccessary fuelburn & extending the engine life, & noise abatement etc. In short, Big Savings for the company, compared to the 'old days'!
If no flex temp is inserted into the MCDU, then the fadec will by default use the sensed OAT(actual) to determine the T.O. parameters for the given ambient conditions, which will be higher thrust than any Flex take off roll, same as TOGA, if you were to select that detent during the roll for any required reason.
Difference between Flex to Toga, is nowadays ones reserve thrust, available at the push of the thrust lever from one detent to the next, if one gets into trouble & needs it, otherwise the engines on almost all big jets these days very seldom ever use/need use, max take off power that they are capable of delivering, for normal conditions! Wet runways & unusual circumstances excluded, naturally.
I expect you know all this, I am elaborating for the benefit of all.