FAA Powerplant Written Practice Test

What is the typical method to correct an out of balance propeller?

1. Removing propeller blades

2. Adding weight on the light side

3. Shimming the propeller base

4. Adjusting engine mount angles

The correct answer is: Adding weight on the light side

Adding weight on the light side of an out-of-balance propeller is a common and effective method for achieving proper balance. When a propeller is out of balance, it often results in vibrations that can lead to increased wear and potential damage to the engine and airframe. The imbalance is usually due to the distribution of weight along the blades. To correct this, mechanics typically perform a dynamic balance check, which identifies the light side of the propeller. Once the light side is determined, strategically placing weight on that side helps equalize the mass distribution. This approach compensates for any discrepancies, allowing for smoother operation and reducing stress on the engine and airframe. This method is preferable because it directly addresses the imbalance by counteracting the uneven weight distribution without permanently altering the propeller itself. Other options, such as shimming the propeller base or adjusting engine mount angles, do not specifically resolve balance issues related to propeller blade weights.