What is the purpose of the Instrument Landing System (ILS)?

• A. All weather approach guidance system
• B. Displays the flight path to line up with runway/carrier deck; by scanning through azimuth and elevation, the system provides continuous measurement of the lateral and vertical deviations from the optimum approach line for the aircraft.
• C. A weather radar display for storms
• D. An autopilot for landing

Answer: (A)

The Instrument Landing System is designed to enable precision approaches in all weather, giving pilots precise guidance to land on a specific runway. It provides lateral guidance to align with the runway centerline through the localizer and vertical guidance to follow the glide path through the glideslope. This setup lets the flight crew (or the aircraft’s flight director/autopilot) fly a stable approach even when visibility is poor, icing conditions exist, or weather obscures the runway. It is not a weather radar, which detects storms, nor is it simply an autopilot for landing, though it can be used to drive flight guidance. It also isn’t meant for carrier deck alignment in general; its primary purpose is reliable, all-weather runway approaches.