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An aircraft is performing an ILS CAT II approach when a car crossed the sensitive area without clearance. The pilot executed a missed approach. What led the pilot to perform a missed approach?
  • A
    LOC and GS indication fluctuations.
  • B
    Magnetic variation change.
  • C
    Change polarisation.
  • D
    Autopilot disengagement.

Effects of infringements of critical and sensitive areas

It has been shown that critical and sensitive area violations have an effect on the aircraft systems. The magnitude and impact of these effects is dependent upon many factors including aircraft type, position, speed, geometry, equipment, size and speed of the violating object. Aircraft systems may absorb short time ILS signal fluctuations through the effects of filtering by on-board equipment and the dynamics of the airframe.
Slow or bias type errors that are not detected by the anomaly detection algorithms result in indications to the pilot either through flags, aircraft control actions (from autopilot) or fluctuations of the cockpit display indicators. The length and magnitude of fluctuations are linked to the speed and time of the critical and / or sensitive area violation.
  • FAA warns pilots of reports that ILS signal integrity is affected by equipment operating within the ILS critical area. " In several cases, the aircraft autopilot followed ILS fluctuations causing the aircraft to pitch and roll excessively" (FAA).

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