In IFR operations, when must a pilot adhere to notified safe altitudes?

In IFR operations, it is essential for a pilot to adhere to notified safe altitudes during both climb and descent phases. This requirement is put in place to ensure the safety of the aircraft by providing necessary obstacle clearance and controlling air traffic. Climb and descent phases are particularly critical as the aircraft transitions between different altitudes, where the risk of collision with terrain or other aircraft is higher if safe altitudes are not followed.

By adhering to notified altitudes during these phases, pilots ensure they are operating within established safety parameters, which help maintain vertical separation from obstacles and other air traffic. It is a fundamental part of maintaining safe and effective flight operations under instrument flight rules.

Other options suggest more limited scenarios or conditions that do not encompass the full scope of a pilot's responsibilities regarding altitude adherence in IFR operations. For instance, it is not only the proximity to large cities or limited visibility conditions that dictate safe altitude adherence; rather, it is a constant requirement during critical phases of flight across controlled airspace.