ISA Deviation

[Eddie]

I've worked out how to calculate this, but how does it affect the FMC's performance calculations?

[dr_anthony]

No way at this moment, all entries on des forecast not affected FMC calc. ISA at sea level + 15 C. It mean, if you have + 25 C at destination (on sea level) - you have + 10 ISA dev.

Temperature changes to -1,98 C by every 1000 ft.

Edited July 21, 2016 by dr_anthony

[Eddie]

No way at this moment, all entries on des forecast not affected FMC calc. ISA at sea level + 15 C. It mean, if you have + 25 C at destination (on sea level) - you have + 10 ISA dev.

Temperature changes to -1,98 C by every 1000 ft.

I was entering ISA deviation for the cruising altitude on the PERF INIT page, not on the descent forecast.

[Litjan]

Different ISA deviations´ effect on performance is not modeled for now - the effect is fairly small (for typical deviations) and X-Plane does not model certain aspects of ISA deviation (like true altitude changing, etc.)

Jan