12.72.8. For a fixed-pitch propeller at a constant throttle setting, explain the relationshipbetween airspeed, angle of attack and rpm. 

As airspeed increases the angle of attack of fixed pitch propeller blade at constant RPM will decrease
If the angle of attack is reduced, propeller torque is reduced and engine RPM will increase
With a fixed pitch propeller the angle of attack varies with forward velocity, and with RPM

12.72.6(d) . thrust and propeller torque. 

12.72.6(c) . total reaction, with its components; 

Total reaction force is

Components
– Thrust – component perpendicular to the plane of rotation
– Propeller Torque – the component in the plane of rotation

12.72.6(b) . relative airflow; 

12.72.6(a) . direction of rotation; 

Thrust
– the component perpendicular to the plane of rotation

Propeller Torque
– the resistance to motion in the plane of rotation

12.72.6. With the aid of a diagram, identify and define the following for a rotating bladesection: 

12.72.4. Explain the reason for blade (or helical) twist.

The helical twist (which is) the reduction in blade angle from hub to tip is
– to gain the most efficient angle of attack along its whole length at airspeed and rpm
– higher rotational velocity towards the tip of the blade will reduce the angle of attack

12.72.2(d) . angle of attack. 

This is the angle between the chord line of the blade section and the relative airflow

12.72.2(c) . helix (or pitch) angle; 

The angle between forward rotational velocity vector and the plane of rotation of the propeller blade is Helix / Pitch angle

12.72.2(b) . blade angle; 

The angle which the chord – line of a propeller section makes with the plane of rotation is the propeller blade angle