Australia Instrument Flight Rating (IFR) Practice Test

The correct choice is when a pilot must set the most accurate QNH before passing the Initial Approach Fix (IAF). This is important because the IAF is the point where an aircraft transitions from en route flight to the approach phase for landing. Setting the most accurate QNH at this point ensures that the altimeter reflects the current local pressure settings, allowing for more precise altitude references during the descent and approach. Proper altitude management is critical for safety, particularly in areas with dense air traffic or varied terrain.

Accurate QNH setting prior to reaching the IAF aids in achieving proper vertical navigation, as pilots receive more accurate altitude indications for maintaining safe separation from the ground and other aircraft. Additionally, using the correct QNH becomes crucial for establishing an appropriate glide path and altitude during the final approach phase.

While other moments, such as before leaving the departure airport, during descent, or upon entering the terminal area, are important for QNH settings, the critical point for accuracy specifically tied to the approach phase’s safety and efficiency is just before crossing the IAF.