A very thorough post from Neru. From an instructor though I would hope for simplicity as well as thoroughness.
- The aircraft flies at a particular TAS. Direction & wind are of course irrelevant for TAS.
- The clouds fly at zero TAS. Ditto direction & wind.
- Therefore direction & wind are irrelevant to the difference in speed between the two.
Now altitude however is quite relevant to TAS - so you should fly just above the layer at 10,000' rather than just above the layer at 3000' for that real feel of speed...
Hmm. Now about that downwind turn:
- The aircraft accelerates (turns) as a function of angle of bank and TAS.
- The wind vector has exactly the same effect on an aircraft at all times, in terms of direction and speed.
- Therefore the wind cannot cause the aircraft to accelerate (turn), unless the wind itself changes.
- Therefore all acceleration (turning) done by the aircraft, in a steady wind, is caused solely by a function of angle of bank & TAS.
- This function of AoB & TAS doesn't have compass bearing in it, therefore one would not expect TAS to change in a turn, unless the wind itself changes.
Hope that works...