A flight control module for computing glideslope deviation during landing of an aircraft, the aircraft receiving first and second instrument landing system, ILS, glideslope signals and computing first and second multi-mode receiver, MMR, glideslope deviation signals with respect to a main landing gear of the aircraft based on the first and second ILS glideslope signals, the flight control module comprising: a communication interface configured to receive inertial data for said aircraft, the first and second multi-mode receiver glideslope deviation signals (424, 426) indicative of respective glideslope deviations computed based on a glideslope transmission received by said aircraft, and an altitude of said aircraft measured by a radar altimeter; a processor coupled to said communication interface and configured to compute a filtered MMR glideslope deviation bv filtering the first and second MMR glideslope deviations, translate the filtered MMR glideslope deviation from the main landing gear to a guidance control point, GCP, for the aircraft; initialize an inertial glideslope deviation computation based on the filtered MMR glideslope deviation when an altitude of the aircraft falls below a predetermined threshold; integrate the inertial data, generated by an inertial reference unit, IRU, for the aircraft, from the filtered MMR glideslope deviation to generate the inertial glideslope deviation with respect to the IRU; and translate the inertial glideslope deviation from the IRU to the GCP; and a signal selection fault detection, SSFD, module configured to select one glideslope deviation from among the respective glideslope deviations (424, 426) and the inertial glideslope deviation for use in controlling an automated landing system of said aircraft. a communication interface configured to receive inertial data for said aircraft, the first and second multi-mode receiver glideslope deviation signals (424, 426) indicative of respective glideslope deviations computed based on a glideslope transmission received by said aircraft, and an altitude of said aircraft measured by a radar altimeter; inertial data for said aircraft, the first and second multi-mode receiver glideslope deviation signals (424, 426) indicative of respective glideslope deviations computed based on a glideslope transmission received by said aircraft, and an altitude of said aircraft measured by a radar altimeter; a processor coupled to said communication interface and configured to compute a filtered MMR glideslope deviation bv filtering the first and second MMR glideslope deviations, translate the filtered MMR glideslope deviation from the main landing gear to a guidance control point, GCP, for the aircraft; initialize an inertial glideslope deviation computation based on the filtered MMR glideslope deviation when an altitude of the aircraft falls below a predetermined threshold; integrate the inertial data, generated by an inertial reference unit, IRU, for the aircraft, from the filtered MMR glideslope deviation to generate the inertial glideslope deviation with respect to the IRU; and translate the inertial glideslope deviation from the IRU to the GCP; and a signal selection fault detection, SSFD, module configured to select one glideslope deviation from among the respective glideslope deviations (424, 426) and the inertial glideslope deviation for use in controlling an automated landing system of said aircraft.