If only things were that simple!
Aircraft performance is much more complex than simple aerodynamics theory.
Engine efficciency is an important element, and this one is a function of many intricate factors.
To start with, forget about thrust being in a direct, constant ratio to fuel flow ....
Then, give me please that unique AOA for best rate of climb with a jet ? ...
Wind is another important factor when it comes to flying best range, best angle of climb, best glide ...
When it comes to keeping a decent safety margin above stall, and especially when you don't have two big engines responding immediately to very sensitive sensors, wind gradiant, and gusts are then of prime importance as well ...
Up to now, I don't know of a single instrument, nor of a single computer program that would dispense a crew member of being a knowledgeable pilot.
Shame on the manufacturers for not puting emphasis on the kind of graph that is dispayed here (
Page 148 of this thread)
Shame on the authorities for not making it mandatory.