Error Propagation Concepts Including Flight Dynamics for Total System Performance Analysis During GBAS based Initial CAT-III Approach and Landing

In order to assess the integrity risk for GBAS based automatic approach and landing, we investigated a total performance concept of a combined system consisting of an ILS look-a-like GBAS landing system (GLS) and a DeHavilland Dash-2 Beaver aircraft. We propagated four basic pseudorange errors to a position error distribution, which was then the source of position uncertainties for the GLS installed in the aircraft. Results show that the vertical total system error (TSE) in the steady state final approach lags behind the vertical navigation system error (NSE). The TSE is smoothed and preserves the general temporal sequence of the error. A reduction of 30\% of the TSE standard deviation with respect to the NSE only occurs during a period of glide slope overshoot, where the autopilot uses large and steadily declining elevator deflections to return to the desired glide path. With minor adaptations this concept can be refined and a possible error reduction may be achieved