Instrument Rating Checkride Practice Test

What is the function of the localizer in an ILS approach?

1. To provide vertical descent guidance

2. To assist with lateral course guidance

3. To mark the decision height

4. To indicate visual references

The correct answer is: To assist with lateral course guidance

The localizer is a crucial component of the Instrument Landing System (ILS) that provides lateral course guidance to ensure that an aircraft is aligned properly with the runway centerline during an approach. It operates by transmitting signals from the ground to the aircraft, which the onboard navigation systems interpret. This precise lateral guidance enables pilots to maintain the correct approach path and minimizes the risk of lateral deviation from the intended flight path, especially in low visibility conditions. The localizer allows for a safe and accurate landing approach and is typically effective in providing guidance up to a distance of about 18 nautical miles from the runway. In contrast, functions performed by other components of the ILS include providing vertical descent guidance, which is handled by the glideslope, marking the decision height through altitude markers displayed in the cockpit, and indicating visual references for transition to visual flight rules upon landing. Each of these functions serves a different purpose within the overall ILS system, making the localizer essential specifically for lateral alignment.