Cockpit Visualization of Curved Approaches based on GBAS

Abstract

The demand for fuel efficient flight paths which include shorter routes and routes adapted to the prevailing terrain as well as the aim to reduce the perceived noise on the ground in the terminal area of airports lead to the development of curved approach procedures. To be able to conduct curved approach procedures, an aircraft is on the one hand required to be able to determine its position very precisely. On the other hand, it is required to be able to follow the required flight path very accurately. The first is usually archived with satellite navigation or a combination of different navigation systems and the latter can be achieved by an autopilot which has to be rather sophisticated when intending to follow a curved approach path. This indicates that an aircraft has to be highly equipped with navigation and guidance avionics systems. To fully exploit the advantages of curved approach procedures, it is desired that the majority of aircraft are able to conduct curved approach procedures even with a less sophisticated degree of equipage. A key enabler for curved approach procedures is a Ground Based Augmentation System (GBAS). It broadcasts pseudorange corrections for all satellites in view to enable airspace users to augment their own position. In addition, it broadcasts desired flight paths. Next to standard “straight-in” Final Approach Segments (FAS), GBAS messages are defined in the RTCA standard DO-246D that provide the possibility to broadcast curved precision approach paths. This Terminal Area Path (TAP) functionality in combination with the augmentation of the user’s position can be used as a sole means to conduct a curved approach. The advantage of this setup is that a high accuracy and a high integrity in the lateral as well as in the vertical position domain can be achieved and the aircraft does not have to be equipped with a current database for the published approach procedures. Different ways to present flight path data were investigated and flight tested in this work.