FAA Powerplant Written Practice Test

If a starter commutator on a reciprocating engine is found with a glazed surface, what should be done?

1. Replace it immediately

2. Apply lubricant to it

3. Clean the surface with sandpaper

4. Polish it with a buffer

The correct answer is: Clean the surface with sandpaper

When a starter commutator on a reciprocating engine has a glazed surface, cleaning it with sandpaper is the appropriate action. A glazed surface indicates that the commutator has become smooth and shiny due to wear or overheating, which can reduce the effectiveness of electrical contact between the brushes and the commutator. Using sandpaper helps to restore the necessary texture to the surface, improving the contact area and ensuring optimal performance and conductivity. This process typically involves using a fine-grit sandpaper to remove the glaze while being careful not to excessively wear down the surface or create deep grooves that could further impair function. The other actions may not address the underlying issue effectively. Replacing the commutator can be unnecessary if it can be restored through cleaning. Applying lubricant would be inappropriate as it could interfere with electrical connections. Polishing the surface with a buffer may create an even smoother surface, which could exacerbate the glazing problem rather than solve it. Thus, cleaning with sandpaper is the most effective and practical approach for restoring a glazed commutator.