Like in your last question, you are asking us to label a figure which you have taken from the Aircademy Ltd. PPL question catalog.
In this case, the figure is from Part-FCL Question Bank 80 – Aircraft General Knowledge, Question 65:
So the one label you have been able to "confirm" is the one already marked out in the question catalog.
What you are looking for to label the remaining points is a propeller blade section velocity diagram. A simple one is provided in Figure 5-44 of the excellent FAA Control Flying Handbook, FAA-H-8083-5. More advanced ones are provided in scientific publications, such as Figure 7 in "An Overview of Model Tests and Numerical Predictions
for Propeller-Ice Interaction"
Velocity diagram for a propeller blade section, $\beta$ is the angle of advance, $\beta_i$ is the hydrodynamic pitch angle, $\phi$ is the geometric pitch
angle, $\alpha_G$ is the geometric angle of attack, $V$ is the carriage speed, $V_A$ is the advance speed, and $U_A$ are the tangential and axial induced velocities, and $P$ is the pitch at $0.7R$.
In short:
| point |
label |
| 1 |
blade pitch (=angle of incidence) |
| 3 |
angle of attack (angle between relative wind and chord line) |
4 and 2 are velocities which are not mentioned in the main course materials and would not be relevant for the exam.
As a general recommendation, I suggest you purchase the training material (textbooks) by Aircademy Ltd., since you are clearly preparing for your exam using their question catalogs. The expense will be inconsequential compared to the rest of your training cost - but it would enable you to look up these figures without having to resort to StackExchange multiple times.
