Originally Posted by
KenV
Why? Because there are numerous "cruise conditions", even on the same flight. How so? The required AOA depends on a variable that is constantly changing: weight. Do you set "best performance" for the conditions at top of climb? Half way to destination? Just before descent? With a completely full passenger load? With a partial passenger load? With full tanks? Partially filled tanks? There are multiple variables that drive weight.
Yes, I've already pointed out that variables can change the day to day (or even minute to minute) condition from the design one. The design condition is the baseline (full of assumptions about altitude, weight, speed, etc.) that all those changes are relative to. (Kinda like air pressure changes all the time and 29.92 is arbitrary, but we still need some baseline for the calculations.) If oil gets too expensive, or New York TRACON is too congested, you'll be cruising at a higher AOA than designed.
But the way I read FCeng's post (maybe I misread, or he'll elaborate) is that even in the original baseline design, which would be reflected in the average of the day to day, it's advantageous to have the fuselage pitched up. That's what I'm questioning.