I am aware that the drag curves are greatly simplified, most likely they are too simple for a small prop a/c too. However, they are enough for the purpose of explaining something in an easy and understandable way. I guess that is why they are used for learning material for
pilots. I don't pretend to be an engineer, I like the KISS principle. I will give you the following.
MRC/ CI zero ≈ Min Drag/min Thrust Required (for practical purposes)
If you say you have a document from Boeing, that states that MRC is slightly higher than Vmd, I believe you (compressibility, TSFC etc.). Still, it has no practical bearing on the discussion about cruise margins (and even strengthens my point of view). Furthermore we can probable put "≈" in every argument in every discussion, starting with why an aircraft flies at all (was it because of Newton or Bernoulli?).
I wish you thirty years of safe cruising Cosmo. Thanks for the conversation.
Thanks, you too. But before you go, I have one more question:
I make a mental note of what Min drag is and don't accept slower speeds.
Not sure what do you mean with "don't accept slower speeds"?
Do you mean that you won't accept a slower speed as
selected speed (say an ATC restriction). And, if so, I assume you mean in high altitude cruise flight only? (in which case I from the beginning agreed, as it is ineffective).
or
You will not accept that the speed temporarily decays below Vmd with wind/temp variations during cruise, and for that reason you will fly with such great margins as to make it unlikely to happen (this is how I interpret your statement). If this is the case, I have to ask a big "WHY?" again. Vmd is not a dangerous speed, flying slower isn't dangerous either. The speed that
is dangerous, is "V drag too great for the thrust at hand to pull you out". Clearly this speed is slower than Vmd.