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Sorry, my post crossed with your amendment.
I will take some time to read the pdf.
However, on quick inspection looking at page 2 there are some problems with his drawings;
Straight and level - OK
Descent - Thrust is less than drag and so this object will be decelerating. No force shown to oppose weight.
Climb - Shows an excess of Thrust which will cause the aircraft to accelerate. Again no force opposes weight in the diagram.
Angle of attack is only one aspect of Coeficient of lift and drag - other aspects can also have an effect.
The wing does not stall at CL Max. It stalls when the angle of attack for CL max is exceeded.
He is correct to say that the best glide is at a tangent to the drag curve.
Unfortunately his diagram is not of the drag curve!
The last page makes sense - in a glider - keep drag down to fly for longer.
As for page 4 - a bit incomplete but it does show that Drag has a verttical component.
Regards,
DFC
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