FAA Powerplant Written Practice Test

If a starter commutator on a reciprocating engine has a glazed surface, what should be done?

1. Replace the commutator

2. Clean the surface with sandpaper

3. Polish with oil

4. Leave it as is

The correct answer is: Clean the surface with sandpaper

When dealing with a starter commutator that has a glazed surface, it is important to restore the surface to its optimal condition to ensure proper electrical contact and functionality. Cleaning the surface with sandpaper is the most appropriate action. Sandpaper can effectively remove the glaze and any residue that prevents good conductivity between the commutator and the brushes. This process helps to restore a rougher, more suitable surface that encourages better electrical connection, which is crucial for the starter's efficiency. Cleaning is an essential maintenance step, and using sandpaper allows for a specific level of abrasiveness that can effectively reduce the shiny glaze without excessively wearing down the commutator. This makes the starter more reliable and increases its longevity, which is critical in maintaining engine performance. Other options, such as replacing the commutator, may not be necessary if the glazed surface can be effectively cleaned. Polishing with oil could create a slick surface, which is counterproductive to the intention of improving electrical contact, and leaving it as is would likely result in continued poor performance and potential failure of the starter.