What might happen if an aircraft is not clean before weighing?

When weighing an aircraft, it is essential that the aircraft is clean to ensure an accurate weight measurement. Dirt, debris, or any additional materials present on the aircraft can add unnecessary weight. This excess weight may lead to an underestimation of the aircraft's total weight if not accounted for properly, which can subsequently affect various calculations related to flight operations, such as performance, fuel requirements, and loading processes.

For example, if the aircraft is weighed with a significant amount of dirt or contaminants, the actual operational weight could be higher than the recorded weight, leading to potential safety issues such as exceeding weight limits or affecting the aircraft's center of gravity. Accurate weight is crucial for ensuring the aircraft operates within its designed performance parameters, making the cleanliness of the aircraft a critical factor in the weighing process.