What is required to start descending along an instrument approach?

To begin descending along an instrument approach, it is essential to be cleared for the approach. This clearance is a crucial part of the standard operating procedures in aviation and ensures that air traffic control is aware of your intentions and has confirmed that the airspace is safe for your aircraft to proceed along the designated approach path.

When you are cleared for the approach, it indicates that you have permission from air traffic control to follow the established procedures and altitude profiles associated with that specific instrument approach. This authorization is contingent on safety factors such as traffic, weather, and runway availability.

The other considerations, such as being aligned with the approach path, while important for safely executing the approach, do not replace the need for explicit clearance. Similarly, minimum visibility and landing clearance are also significant aspects of the approach but come into play at different stages of the overall landing process. Thus, the requirement for being cleared for the approach is paramount before commencing the descent.