On a Bus, TOGA is used if the runway is contaminated (wet/icy), if you are going around or if performance (high/hot/short runway) dictates it is required. Otherwise T/O Flex is used.
T/O flex provides less power, less risk of a failure during climb out coz the engines aren't screaming and wears the engines less resulting in cheaper costs in the long run; without compromising safety.
Setting the engines to Flex or TOGA provides the appropriate Flight Director commands, updates the FMS etc. When the thrust is moved back from Flex or TOGA the Autothrust then engages.
Ghost
