Airborne Integrity Monitoring for a General Aviation Differential-GNSS Instrument Approach System (DIAS) Avionics

N. Chiarini, M. Zanzi, M. E. Penati, M. Crisci

Department of Electronics, Computer Science and Systems (DEIS), University of Bologna

Viale Risorgimento 2, 40135 Bologna, Italy

This paper focuses on the problem of the continuity of integrity for a general aviation avionics that supports DIAS procedures. In this paper the airborne integrity monitoring process adopted in the FODIAS project is presented. It can be see that a baro-inertial altitude can extend the availability of Vertical Protection Levels over periods where the DGPS solution is not available. This is accomplished by a series of Kalman filters processing different sets of measurements.

Since the beginning of 1999 the University of Bologna started to develop the FO-DIAS project, a Differential-GNSS Instrument Approach System (DIAS), located at the Forlì (FO) airport, meant to General Aviation aircraft and able to allow CAT I approaches (Chiarini, Zanzi, 1999). In Forlì airport relevant activities are performed for pilot education, so General Aviation flights are the majority.

An objective of FO-DIAS project is to design an avionic system, suitable for general aviation airplanes already certified for IFR, that enables them to perform category I precision instrument approaches to all the airports where DIAS procedures will be published.

Specifically, the project consists of the design of two main systems: a LAAS ground station, whose design has been carried out according to the specifications stated in RTCA 245 (this is a development task of TELIT, an Italian company that participates to the FODIAS project), and a low cost avionic system capable to satisfy the Required Navigation Performances (RNP) stated by ICAO in terms of accuracy, continuity, integrity and availability at least for Performance Type (PT) 1. In this work it is shown how baro-inertial altitude, given by the ADR, can increase the continuity of the integrity. This is possible by a set of kalman filters processing different sets of informations. Further work now it has to be done for the horizontal dimensions where no so stable inertial position information as in the vertical case are available.