This paper presents a simple and so easily implementable threshold and up-down counter-based voting algorithm for the fault detection of aircraft position information during landing. Easy implementation is inevitable in case of small unmanned aircraft due to the size weight and power consumption constraints. Most of the development is based-on real flight test data collected in frame of the VISION EU H2020 research project on a 4m wingspan aircraft. The aircraft’s position flight measurements were provided by an on-board GPS unit with SBAS correction and an on-board data-based inertial-barometric-camera sensor fusion ESKF algorithm. ILS was simulated as the aircraft and airport were not equipped with it. SBAS, ILS and ESKF errors were all artificially added to the nominal flight and simulated data. Pairwise comparison of position information is the basis of fault detection. Category I precision approach requirements are considered to tune and test the fault-detection algorithm first, by the selection of thresholds and then by the fine tuning of up-down counters to reduce false alarms. Both integrity risk and time-to-alert requirements are satisfied only the continuity risk resulted below the expected but this does not mean needless abortion of landings.