777-300ER Engine anti-ice
We use ACARS performance data and in the take-off WAT, we specify if there's visible moisture...the WAT utilizes the latest METAR for met data.
At times when OAT is about 8 or 9º and there is visible moisture, we are required to use Eng Anti-Ice. After start we turn on the Eng Anti-Ice. Sometimes we get a ENG ANTI-ICE EICAS message. Checking the TAT it shows 11º...the EICAS procedure has us turn off the Eng Anti-ice.
Clearly the EICAS system uses the TAT to make the decision to post the EICAS message, but the ACARS WAT is using the METAR value of OAT.
What would be the prefered option? Leave Eng Anti-ice on and cancel the EICAS message or turn off the Eng Anti-ice??