How does an ILS/LOC navigation receiver function and what faults might degrade its performance?

How does an ILS/LOC navigation receiver function and what faults might degrade its performance?

• A. It decodes localizer and glideslope signals to provide course deviations; faults include degraded sensitivity, misalignment, and interference.
• B. It transmits weather radar data to the cockpit.
• C. It calculates fuel burn using GPS data.
• D. It records flight data for post-flight analysis.

Answer: (A)

An ILS/LOC receiver works by picking up the runway’s localizer signal for horizontal guidance and the glideslope signal for vertical guidance, both broadcast from ground-based antennas. The airborne receiver demodulates these VHF signals and compares the relative strength of the modulated components to determine how far off the aircraft is from the centerline and from the proper glide path. That deviation information is shown on the cockpit indicators (CDI for horizontal deviation and the glide path indicator for vertical deviation) and can be used to steer the airplane back to the center and onto the correct approach path. Faults that degrade performance include degraded sensitivity, which reduces the ability to detect small deviations or weak signals; misalignment of the localizer or glideslope antennas, which can bias the guidance; and interference or clutter from other radio sources or multipath, which can corrupt the signal and produce false or unstable indications. These issues directly affect the accuracy and reliability of the deviations that guide the approach. Other system functions described in the other options are not what an ILS/LOC receiver does: weather radar data transmission, GPS-based fuel calculations, and flight data recording are handled by different systems.

An ILS/LOC receiver works by picking up the runway’s localizer signal for horizontal guidance and the glideslope signal for vertical guidance, both broadcast from ground-based antennas. The airborne receiver demodulates these VHF signals and compares the relative strength of the modulated components to determine how far off the aircraft is from the centerline and from the proper glide path. That deviation information is shown on the cockpit indicators (CDI for horizontal deviation and the glide path indicator for vertical deviation) and can be used to steer the airplane back to the center and onto the correct approach path.

Faults that degrade performance include degraded sensitivity, which reduces the ability to detect small deviations or weak signals; misalignment of the localizer or glideslope antennas, which can bias the guidance; and interference or clutter from other radio sources or multipath, which can corrupt the signal and produce false or unstable indications. These issues directly affect the accuracy and reliability of the deviations that guide the approach.

Other system functions described in the other options are not what an ILS/LOC receiver does: weather radar data transmission, GPS-based fuel calculations, and flight data recording are handled by different systems.