FAA Powerplant Written Practice Test

What happens when steel valve seats are sanded during an overhaul?

1. They become smoother

2. They can be wet or dry sanded

3. They must not be touched

4. They require replacement

The correct answer is: They can be wet or dry sanded

When steel valve seats are sanded during an overhaul, the correct understanding pertains to the fact that they can indeed be both wet or dry sanded. This method of sanding is utilized to improve the mating surface for a good seal between the valve and the seat, which is crucial for engine performance. Wet sanding helps to minimize the generation of dust and can reduce the risk of overheating the material, while dry sanding allows for more direct removal of material. This sanding technique is necessary to restore the surface finish and correct any imperfections that may have developed over time due to wear or damage. Proper techniques ensure that the valve seats remain within specifications for proper engine operation. While there are important limitations and care that need to be taken not to over-sand or damage the valve seats, they do allow some maintenance to keep them functioning effectively. Options that mention not touching or requiring replacement are overly restrictive considering the context of maintenance and overhaul practices, while the idea of becoming smoother, while potentially true, does not cover the operational aspect of the sanding process compared to the reference of wet or dry methods.