Sorry Compressor stall, I still don't understand. Could you give an example using your formula?
You quote from the FCOM:
When the temperate is lower than ISA:
‐ The true altitude of the aircraft is lower than the altitude that the ADIRS computes.
‐ The FPA that the aircraft actually flies, is less steep than the FPA that the ADIRS computes
The way I understand: when it's colder than ISA: If you select FPA-3.0, and it's minus 30 degrees outside, the actual FPA flown by the plane will be lower than 3.0 degrees, so according to the correction table above, the crew needs to set FPA -3.3 degrees on the FCU. Am I correc?
That's why I don't understand when you say: It ''thinks'' it's higher then it is.
Thank you.