Which term refers to a navigation aid that provides both horizontal and vertical guidance to a runway?

• A. Instrument Landing System
• B. Inertial Navigation System
• C. GPS Approach System
• D. VOR/DME

Answer: (A)

Providing both horizontal and vertical guidance to a runway is a hallmark of a precision approach system known as the Instrument Landing System. It uses two signals: the localizer delivers lateral guidance to keep you centered on the runway, while the glide slope provides vertical guidance to follow a precise descent path to the runway threshold. This combination lets you align with the runway and descend along a defined path, even in poor visibility.

Inertial navigation systems mainly supply position, heading, and velocity information and don’t offer a runway-specific glide path. GPS approach systems can include vertical guidance in some procedures, but they are separate systems from the traditional ILS and not universally described as the standard means of providing both lateral and vertical guidance to a runway. VOR/DME offers lateral guidance and distance information but lacks the vertical guidance component.