Is the only reason why Emirates does not use DeRated take off is for Safety or is there another reason? Do they do that for all their fleet?

They don't use standard thrust derate values but I believe they still use assumed temperature to do reduced thrust takeoffs.

They don't use standard thrust derate values but I believe they still use assumed temperature to do reduced thrust takeoffs.

 

Thats correct Emirates do not use a derate they use an assumed temperature.

It's normal for some airlines to use a combination of both, correct?

in LAN for the 787 we use the combination of both's. the problem with derated is, that in the event of a engine failure, the use of toga thrust may produce a loss of control.