When are you allowed to descend from 10,000 MSL after crossing the Sidon VORTAC and cleared for the approach?

The correct answer indicates that descent from 10,000 MSL is permitted at 4 DME or beyond and on the 300 course outbound after crossing the Sidon VORTAC and being cleared for the approach. This aligns with standard operating procedures for aircraft on an approach, which often include specific descending points based on distance and designated courses.

When an aircraft is cleared for an approach, there are typically published procedures that specify altitude restrictions and when to descend. The use of DME (Distance Measuring Equipment) from the VORTAC to determine descent points helps ensure that pilots maintain safe altitudes while they are in the airspace. Being on the outbound course after crossing the VORTAC reinforces that the aircraft is established on the correct track for the approach.

In contrast, other options involve conditions that might not provide the necessary safety or adherence to standard approach protocols. In some cases, descent can only occur based on the latest clearance or altitude restrictions provided by ATC, which relates to the second option. The third option suggests immediate descent upon crossing the VORTAC, which is not standard procedure for approach safety. Lastly, the fourth option implies a fixed altitude change rather than a distance-based approach instruction, which would not align with typical operational guidance