What does "zeroing" mean in the context of rigging adjustments?

In the context of rigging adjustments, "zeroing" refers to setting controls to their neutral positions before making further adjustments. This step is crucial because it establishes a baseline for any subsequent modifications to the control surfaces. By starting from a neutral position, the technician ensures that any adjustments made will be more accurate and can be evaluated in relation to a consistent reference point. This practice helps maintain the aircraft's control response as intended and prevents unintended adjustments that could affect performance and safety.

The other options, while related to aircraft operations, do not pertain to the concept of rigging adjustments. Aligning the aircraft on the runway is about positioning rather than control surface settings, calibrating the altimeter deals with altitude readings, and adjusting control surfaces to maximum deflection is focused on extremes rather than establishing a neutral baseline.