PPRuNe Forums - View Single Post - Descent profile when cleared for an ILS approach?
Old 17th March 2019 | 22:51
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FlightDetent

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From: Commuting not home
RMC, somewhere in ICAO Doc 8168 I once found the equation to calculate the altitude corrections for non-ISA temperature.
Do not take my word for it without checking, IIRC the DELTA needed to get the true geometrical HEIGHT above the measuring point were more or less the same for the warm temperatures as they were for the cold ones.

The catch was the reference "zero" - it is SL @ 15 DEG centigrade. I.e.

For COLD temperatures the correction down to 0°C (ISA -15) is negligible.
For HOT temperatures, in a similar fashion, until you hit ISA +15 the difference is not that relevant.

If you only have the COLD tables, to get a taste about the HOT deviation you may attempt :

OAT 40 deg at SL = ISA+25
----- reverse -----
ISA -25 = -10 deg Centigrade
==> use the values for -10 degrees and apply them in the opposite sense, to get a taste of the HOT air deviation.

Last edited by FlightDetent; 18th March 2019 at 00:33.
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