During radar vectoring, when should you maintain the last assigned altitude?

Maintaining the last assigned altitude until established on a segment of a published route or Instrument Approach Procedure (IAP) is rooted in ensuring safe and effective separation from other aircraft and a controlled descent as you transition into the final approach phase.

During radar vectoring, air traffic control (ATC) may provide vectors to guide you towards the intended path for landing. However, while you are still being vectored, it is crucial to maintain the last assigned altitude to avoid conflicts with other traffic that may be in the vicinity. As you reach a point where you are aligned with a leg of a published route or the IAP, this is the point where the lateral and vertical navigation becomes defined and predictable. This helps ensure that you are within the safe altitude ranges and provides the controller with confidence that you are following the designated path.

This procedure allows for a structured transition to the approach phase and helps pilots manage altitude changes effectively without compromising safety. It also aligns with standard protocol where the clearance for approach or other altitude instructions will be provided subsequently, thus reinforcing the need to stick to the last assigned altitude until established on the intended route.