Flight control system with low-frequency instrument landing system localizer anomaly detection and method of use

A flight control system for landing an aircraft, said flight control system comprising:

• a communication bus;
• a global positioning system (GPS) coupled to said communication bus and configured to transmit a GPS position of said aircraft onto said communication bus;
• a multi-mode receivers (MMR) coupled to said communication bus and configured to transmit an instrument landing system (ILS) localizer deviation onto said communication bus, the ILS localizer deviation generated according to received ILS localizer signals;
• and
• a flight control module coupled to said communication bus and configured to:
• receive inertial data for said aircraft, the GPS position, and the ILS localizer deviation on said communication bus,
• compute a GPS localizer deviation and an inertial localizer deviation, and
• detect a low-frequency anomaly in the received ILS localizer signals based on variances in the ILS localizer deviation relative to an average localizer deviation computed for the GPS localizer deviation and the inertial localizer deviation.

A method of detecting a low-frequency anomaly in an instrument landing system (ILS) localizer signal received by an aircraft during landing, said method comprising:

• receiving an instrument landing system (ILS) localizer signal;
• computing a ILS localizer deviation based on the ILS localizer signal;
• controlling the aircraft according to the ILS localizer deviation;
• computing a global position system (GPS) localizer deviation;
• computing an inertial localizer deviation;
• computing an average localizer deviation of the GPS localizer deviation and the inertial localizer deviation;
• detecting the low-frequency anomaly when a difference between the average localizer deviation and the ILS localizer deviation exceeds a threshold;
• and
• controlling the aircraft according to the inertial localizer deviation after detecting the low-frequency anomaly.