FAA Powerplant Written Practice Test

What is the function of moveable counterweights in radial engine aircraft?

1. To enhance fuel efficiency

2. To reduce dynamic vibrations

3. To increase the engine's thrust

4. To improve maintenance accessibility

The correct answer is: To reduce dynamic vibrations

Moveable counterweights in radial engine aircraft primarily serve to reduce dynamic vibrations. Radial engines inherently produce significant vibrations due to their configuration and the arrangement of their pistons. This vibration can lead to operational issues and fatigue in engine components as well as discomfort for passengers and crew. The moveable counterweights are strategically placed and can be adjusted to counteract the vibrations generated during engine operation. By shifting these weights, the radial engine can achieve a more balanced state, leading to smoother operation. This balance helps to ensure that the engine runs more efficiently and prolongs its lifespan by minimizing wear and tear caused by these vibrations. While the other options mention fuel efficiency, thrust, and maintenance accessibility, they do not directly relate to the primary role of moveable counterweights in managing engine vibrations, which is crucial for the overall performance and longevity of radial engines.