I have noticed on the ALTN page, PG1 gives you the 4 closest alternates at any given time, unless I override this with the ICAO designator that I choose to be as a more suitable alternate.
What are the fuel and ETA predictions when selecting any one of these ALTNs based upon, if I do not change anything on the second page?
Does this page use the same philosophy as the fuel and ETA predictions on the ACT RTE data page, based in actual winds entered and mixing 200 nm ahead between actual and predicated?
When selecting to divert from this page, does it predict fuel and ETA based direct to the aerodrome reference point?
I have noticed that if I choose an ALTN from this page, then type the same ALTN ICAO designator into the 3L (DEST) on PROGRESS page, the fuel and ETA predictions are not the same nor anywhere near. I have noticed discrepancies of up to 2T
and times of about 10 mins
Having looked through my FCOMs I cannot find enough information on why the differences and to where the ALTN page bases its fuel and ETA predictions.
Any help is greatly appreciated.