What are the two antennas usually required for an ILS system?

What are the two antennas usually required for an ILS system?

• A. VOR and DME
• B. ADF loop and sense
• C. Glide slope and localizer
• D. Localizer and glide slope reflector

Answer: (C)

The essential idea is that an ILS provides two guidance cues—one horizontal and one vertical—through two dedicated antennas. The best answer is the combination of glide slope and localizer because these are the two antennas that form the ILS approach: the localizer supplies lateral guidance to keep you on the runway centerline, while the glide slope provides vertical guidance to establish the proper descent path to the runway. The localizer antenna is placed at the far end of the runway and creates a beam that guides you left or right to align with the centerline. The glide slope antenna is positioned near the approach end and generates a vertical guidance signal that tells you whether you’re too high or too low on the descent, typically aiming for a 3-degree glide path. Together, they give precision on both axes to land safely. Other options don’t fit because VOR and DME are separate navigation aids, not part of the ILS approach’s two main antennas; an ADF loop and sense pertain to ADF navigation, not ILS; and a reflector isn’t used for ILS—the system relies on dedicated transmitter arrays, not a reflector arrangement.

The essential idea is that an ILS provides two guidance cues—one horizontal and one vertical—through two dedicated antennas. The best answer is the combination of glide slope and localizer because these are the two antennas that form the ILS approach: the localizer supplies lateral guidance to keep you on the runway centerline, while the glide slope provides vertical guidance to establish the proper descent path to the runway.

The localizer antenna is placed at the far end of the runway and creates a beam that guides you left or right to align with the centerline. The glide slope antenna is positioned near the approach end and generates a vertical guidance signal that tells you whether you’re too high or too low on the descent, typically aiming for a 3-degree glide path. Together, they give precision on both axes to land safely.

Other options don’t fit because VOR and DME are separate navigation aids, not part of the ILS approach’s two main antennas; an ADF loop and sense pertain to ADF navigation, not ILS; and a reflector isn’t used for ILS—the system relies on dedicated transmitter arrays, not a reflector arrangement.