Which component is used to determine the vertical guidance in an ILS approach?

The component that provides vertical guidance in an Instrument Landing System (ILS) approach is the glide slope. The glide slope is part of the ILS and gives pilots directional information about their vertical position in relation to the desired angle of descent, usually set at about 3 degrees. This information helps ensure that the aircraft descends at the correct rate to safely reach the runway threshold.

In an ILS approach, the glide slope antenna transmits signals that guide the aircraft’s descent path. Pilots monitor the glide slope indicator in the cockpit, typically displayed on the aircraft's flight instruments, to maintain the correct vertical path while approaching the runway. If the aircraft is above or below the ideal glide slope, the indicator will provide feedback to help the pilot make adjustments to maintain the correct descent profile.

Other components like the localizer provide lateral guidance, while the marker beacons signal when the aircraft is at certain points along the approach, and the antenna system itself is necessary for transmitting signals but does not directly provide guidance. Understanding how the glide slope functions is crucial for executing a successful ILS approach and landing under IFR conditions.