For RWYs 4, 31L/R, and 36, when should you report the Initial?

When you are operating in the vicinity of runways 4, 31L/R, and 36, reporting initial means indicating your position to air traffic control as you approach to land or transition into the traffic pattern. In this context, reporting "abeam Pt. Dimmitt" is the most appropriate choice.

Reporting abeam is a standard procedure used by pilots to inform air traffic control of their position relative to a known point on the ground, which helps maintain situational awareness for both the pilot and the controller. This specific reporting point provides a clear and recognizable point for air traffic control to reference, ensuring a more organized and controlled traffic flow.

The other options do not serve the same function or may lead to ambiguity in communication. For instance, reporting at the threshold of the runway, while being a critical point, does not provide an adequate initial position report given the need to inform about your approach well before reaching the runway. Similarly, crossing the runway centerline or reporting at the midpoint of the runway are actions that occur during the landing phase rather than during initial approach, making them less relevant for the purpose of reporting initial position effectively in the traffic pattern.