True Altitude?

[Soldier_Fortune]

Originally Posted by KG26_Alpha

I'm pretty sure ambient temperature, at ground level at least, has been modeled for a long time.

The fact they produced a v4.11 "read me" showing map temps doesn't mean they were not present long before v4.11

Desert maps ambient temps were @ 80-90' back on v4.07 iirc
You only had to look at the temp gauge on your aircraft with the engine off on the runway to see ambient temperature was in the map.
Which was always a bit strange as the engine was cold but the temp gauge registered outside temp.

I can't recall if the ambient temperature was present long before the patch 4.11: frankly I never paid atention to the outside temperature gauges until several weeks ago.
Now I've the game updated to 4.12.1 and I'll not downgrade it to a previous version to check that.
Might be those gauges originally were present for 'flavor' purposes only, without any other appreciable effect on the game's behavior (it wouldn't be the first time nor the last we saw something like).
But the fact is the IAS/TAS charts show the outside temperature was constant, it being 0 ºC for any map and any altitude, and we know they worked perfectly.

As I was telling you, I never paid atention to the outside temperature gauges until several weeks ago. And it was accidentally: while I was testing a bomb mission flying a B-25, I looked at the TAS gauge in the bombardier post after setting the bombsite with the aid of the IAS/TAS chart, and I saw that there were significant differences between the two readings. And I thought: "Shit! Is it a new bug?"
After some calculations with the E6-B, I could see the TAS gauge's reading was true. And looking to the outside temperature gauge for my very first time, I saw that the reading matched that of the real atmosphere for that altitude.

I have conducted numerous tests to confirm this, flying different planes in different maps.

Air density at altitude is the interesting factor though it seems something had changed.

It is very important to understand that ground level temperature, altitude and density are closely related, and all together influences the TAS.

The standard formula for the air density at a given altitude below 11,000 m is:

AIR_DENS(Z) = AIR_DENS(0) * [(TGL + LAPSE_RATE * Z)/ TGL]^4.25

Where:
AIR_DENS(Z): air density at a given altitude Z
AIR_DENS(0): air density at 0 m ASL (1.22 kg/m3)
TGL: free air temperature on the surface (std temp = 288.15 ºK or 15.15 ºC). This temperature may be different than the standard temperature.
LAPSE_RATE: -0.0065 ºK/m, it is the constant rate at which temperature decreases with altitude.
Z: altitude ASL, measured in m.

So that formula explains why a plane, flying at a given altitude, may fly at a slower or faster TAS regarding of the Ground Level temperature.
The E6-B allows a pilot to calculate the TAS in one step, knowing the outside temperature, the indicated altitude and IAS: he doesn't need to know or to calculate the air density.

A word form TD would be enlightening.

+1.