What does the Instrument Landing System display to guide an aircraft during approach?

• A. Display on HUD and ARI showing flight path; decodes azimuth and elevation; continuous deviations.
• B. Ground-based weather data display only
• C. Landing gear status display during approach
• D. In-flight entertainment data for passengers

Answer: (A)

The key idea is that the Instrument Landing System gives you precise approach guidance by providing both lateral and vertical cues that are continuously updated as you descend. The localizer handles azimuth, showing how far left or right you are from the runway centerline, while the glideslope handles elevation, showing how far above or below your descent path you are. Those cues are most usefully presented on the cockpit’s head-up display and Attitude Reference Indicator so you can see the flight path relative to the horizon and your attitude at the same time. The combined display lets you steer the aircraft along the correct path by making small, real-time corrections to stay centered on the approach and on the glide path, even in reduced visibility. Other options don’t provide this integrated, real-time guidance of both lateral and vertical deviations.