Airbus X Fuel Planner: Total Air Temp?

[Raffael Walther 0]

Hello

 

I have a question regarding the Airbus X Fuel Planner. 

Do I have to enter the actual or the difference to the ISA-temperature into the field "Total Air Temp"?

 

Background of my question

On official wind and temperature charts there are often temperatures far below -50°C but its not possible to enter temperatures below -50°C into the Fuel Planner.

 

Example

The temperature chart predicts a temperature of  -55°C at my cruising FL.

Do I now enter:

1. -50°C (the lowest possible temperature)
   OR
2. "ISA-temperature at FL390" - "actual temperature" = (-55) - (-56.5) = +1.5°C

 

Best Regards

Raffael Walther

[Raffael Walther 0]

Point 2 should be:

 "actual temperature" - "ISA-temperature at FL390" = (-55) - (-56.5) = +1.5°C

 

PS:

Unfortunately there is an error when I try to edit my initial post.

[Mladen 55]

Hi!

Take a look here:

https://allaboutairplanes.wordpress.com/tag/air-temperature/

For simulation purposes we can use RAT=TAT

Using the "Speed/Temperature Conversion" table, using your planned cruising Mach number and temperature (OAT) at your cruising level, you can find out RAT (TAT).

For example, if you plan to cruise at Mach 0.78 and temperature at your cruising level is -54*C then RAT (TAT) is -28*C

The formula used:        TAT=OAT * (1 + 0.2 * (Ma)^2)                  TAT and OAT are in degrees Kelvin

Hope this helps

 

Mladen

[Raffael Walther 0]

Hello Mladen

 

Thank you for the explanations. I've mixed up TAT with SAT and I didn't know that there are even more temperatures. 

 

Regards

Raffael Walther

[Mladen 55]

Hello Raffael,

You are most wellcome!

 

Mladen

[mopperle 4162]

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