When can you start a descent from an assigned altitude while on an approach?

Starting a descent from an assigned altitude while on an approach should occur when you have been cleared for the approach and are established on a published segment of the approach procedure. This means you should only begin your descent after you have received explicit clearance from air traffic control to ensure safety and compliance with air traffic regulations.

Establishing on a published segment indicates that you are following the designated path outlined in the approach charts, which is designed to ensure safe and efficient navigation toward the runway. These segments may include altitude restrictions, turning points, and glide slopes that are crucial for a safe landing. Therefore, maintaining proper situational awareness and adhering to ATC instructions helps in managing the descent safely and effectively.

The other options suggest various scenarios that either do not align with standard operating procedures or are too vague. For example, descending halfway to the runway or based solely on personal judgment does not guarantee that the required clearances and safety protocols have been observed, and waiting until after reaching the assigned altitude does not incorporate the necessary conditions set by air traffic control, which is fundamental for safe operations.