Stall- Stagnation point- Parts of aircraft- Critical angle of attack

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What are the major parts of an aircraft?
Main wing
Tail wing
Powerplant
Fuselage
Landing gear

What is the reason for stall? Define critical angle of attack?
If the angle of attack for an aerofoil increases from zero deg, you can watch the increase in lift and drag. If you keep on increasing the AOA, at some point sudden loss of aerodynamic forces will occur. Aerofoil can create aerodynamic forces in a large magnitude when attached flow of air occurs at aerofoil surface. 


As the aerofoil gets increased AOA, the flow of air starts detaching from the aerofoil surface. If fully detached then no aerodynamic forces will be generated. That is what the reason for stall. The angle at which stalling starts is the critical angle of attack.

What is stagnation point?

Stagnation point is the point in the airflow where the velocity gets its zero magnitude because of the presence of object in airflow. The flow deviates/joins between upper and lower surface of the object from this point only.

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