Originally Posted by
Fursty Ferret
I’d need to double-check this but if wing or engine anti-ice is turned on while the engine is at take-off thrust, I think the FADEC will maintain the thrust setting at the expense of EGT margins.
No, it won't. The FADEC receives the bleed status from the aircraft, and will automatically derate the max TO thrust to account for the bleed debits (in some cases it will also debit max climb, but I don't recall if that applies to the 777 or if it does, which engines).
The FMC will likewise derate the max TO rating to account for the engine bleed - so it's somewhat transparent to the crew unless you're using the charts to manually calculate the max TO limits. If Engine AI is selected for TO, the FMC will likewise decrease the max TO weight due to the EAI max thrust reduction.
The exception to this would be if the FADECs are in Alternate mode, they don't do the bleed debits, but the FMC still should.