I'm not sure any of us really have a good idea of what is happening or else we would have this solved by now! I am entertaining the thought that it could be different from what I initially thought.
I understand ELR to be the actual lapse rate that you would measure. I do agree that it varies with altitude but if we assume that the lapse rate is actually constant all the way up to the tropopause, what else would change? Dewpoint is also changing - usually dropping, which means that the quantity of water per cubic metre in the air is dropping. But is the quantity of water per cubic metre dropping because of the expansion - or is it something else? If it was exactly because of expansion, then the water quantity per cubic metre should remain constant at the same absolute pressure, thus not affecting the density.
to maintain constant power, correct manifold pressure by approx 0.18"Hg for every 10F variation in induction air temperature from standard altitude temperature. Subtract manifold pressure for temperature below standard.
The charts would be based on a standard atmosphere so this would correct for a non-standard atmosphere. Assuming the lapse rate remains constant (and all other factors constant), wouldn’t ft be correct in saying that if you keep the same absolute pressure, the temperature should be the same?
ft decided “the ideal gas law seems to be valid to use for the lapse rate” by using your figures that were already derived from the standard lapse rate! I thought you'd spotted that little error.
I didn't really show he was wrong, I just said that it didn't necessarily prove something. The standard lapse rate is based on that ideal gas law and that's what ft showed.
I'm no expert with this stuff, but I don't believe air moves 100% adiabatically in the atmosphere and I don't believe air will go from the dry adiabatic lapse rate, immediately to the saturated (moist/wet) adiabatic lapse rate as soon as any moisture is present. If you want examples, look at a METAR and then calculate the cloud base based on the dry adiabatic lapse rate and dewpoint lapse rate (2.5/1000') and you'll find that most of the time the cloud bases will be different than calculated. I’m currently studying meteorology in more depth now so I’m hoping to find more answers that might help answer this MAP scenario. There are articles out there that will explain why the SALR is not actually constant.
I would certainly be hesitant to question credible texts on the basis of various ramblings in this thread.
I'm not hesitant to question texts - they're only credible if they can stand up to questioning and prove they are correct. However, I am hesitant to discredit what a 'credible' text says. I do think the JAA books are credible from what I've seen so far...