What component of the ILS provides vertical guidance during an approach?

The glide slope is the element of the Instrument Landing System (ILS) that provides vertical guidance during an approach. It operates by transmitting signals that help pilots maintain the correct descent angle toward the runway, typically set at around three degrees. This guidance is crucial for ensuring that the aircraft descends at a safe and appropriate rate, allowing for a successful landing, particularly in low visibility conditions.

The localizer, while also a component of the ILS, is responsible for providing horizontal guidance, helping pilots align the aircraft with the centerline of the runway during the approach phase. The marker beacon is associated with the ILS, but it indicates distance from specific points along the approach path rather than providing guidance information. Lastly, VOR (VHF Omnidirectional Range) is a type of navigation aid that provides lateral position information but does not offer the vertical guidance necessary for the approach. This differentiation highlights the unique role of the glide slope in the ILS system.