What device is primarily used to visualize an aircraft's flight path during instrument approaches?

The Instrument Landing System (ILS) is primarily used to visualize an aircraft's flight path during instrument approaches by providing precise guidance for landing. It consists of two main components: the localizer, which helps the pilot align the aircraft with the runway centerline, and the glide slope, which provides vertical guidance for the correct descent angle. This combination allows pilots, especially in low-visibility conditions, to follow the defined flight path accurately, ensuring a safe and controlled approach to the runway.

While the Global Positioning System (GPS) does offer navigation capabilities and can facilitate approaches like GPS approaches, it doesn't provide the same level of precision and guidance specifically tailored for landing as ILS does. The autopilot system, although it can assist in maintaining the flight path, relies on external systems like ILS or GPS to make informed decisions on approach. The Ground Proximity Warning System (GPWS) provides alerts to prevent controlled flight into terrain but does not visualize the flight path itself. By understanding these functionalities, it's clear why the Instrument Landing System is the key device for visualizing flight paths during instrument approaches.