Final answer:
When performing a static balance on a two-bladed propeller, measurements are taken with the propeller in horizontal (0 and 180 degrees) and intermediate positions (often 90 degrees apart) to ensure even weight distribution for balance in all operating positions.
Step-by-step explanation:
When performing a static balance on a two-bladed propeller, measurements must be taken at various positions to ensure the propeller is in static equilibrium. The positions correspond to different orientations the propeller can be in during operation.
These include the horizontal position, with one blade pointed up and one down (0 and 180 degrees), and possibly several intermediate positions, often at 90 degrees apart (90 and 270 degrees).
This ensures that the weight distribution is even throughout the rotation, which is critical to maintaining the balance of the propeller in all positions. The blades must be like long airplane wings and free to rotate about their longitudinal axis during this process.
An imbalanced propeller can create vibrations that lead to inefficiencies and potential damage to the aircraft. This concept of static balance is similar to how a torque balance operates, where a beam remains level when the torques on either side of a fulcrum are equal, just as a statically balanced propeller remains in any chosen position without rotating.
Additionally, knowing that helicopter blades rotate in opposite directions to counteract rotational torques and to eliminate the need for a tail propeller provides an example of how balance and equilibrium are essential to rotorcraft performance.