original question:
2) The same Boeing chart shows the total drag curve at all speed ranges. The level of drag at mach 0.8 is the same as mach 0.67 for the level flight 35,000 feet 70 Tonne 737).
The second question is: can I assume the total drag in a climb at mach 0.8 is the same as the total drag in the climb at 0.67?
My answer - assuming that we are comparing climbs of equal RoC -
nope.
The parasitic drag components will remain unchanged (no change in speed). The induced drag of the slower case will go down farther, since the AoC will have to be greater to achieve the same RoC, and from our previous discussion re question 1, the greater is AoC, the smaller is required lift and thus the smaller is induced drag. On top of that, in the slower case, the induced drag component is a greater proportion of total drag to begin with, making the above reduction even more poignant.
What do I win?
bm