Murphy’s Law Squared - Flight Testing of Automated Closely Spaced Parallel Approaches

Robert Geister, German Aerospace Center, DLR, Braunschweig, Germany
Hayung Becker, German Aerospace Center, DLR, Braunschweig, Germany

Abstract

Nowadays hub airports are facing challenges when trying to expand due to the increasing number of flights and passengers. Terrain and political issues may restrict the opportunities to increase runway capacity (e.g., insufficient space for the construction of a new runway). In addition, the international air traffic becomes more and more complex and therefore, there is a growing demand for new operational procedures. Airports with a dependent (distance of runway centerlines less than 1035m) parallel runway system suffer from a decrease in capacity in Instrument Meteorological Conditions (IMC) as separation margins have to be greater than for independent runways due to the threat of wake vortices.

In this work the methods and findings of conducted flight tests regarding an automated approach procedure are presented. The procedure aims to increase the capacity of a dependent parallel runway system. Based on the visual procedure used at San Francisco airport one approaching aircraft (the “leading” aircraft) is flying a standard approach procedure (i.e., RNAV or ILS) with certain time constraints while a second aircraft (the “trailing” aircraft) is flying a parallel approach that leads to a merge point from which on the two aircraft are flying nearly parallel with approximately 15 seconds separation.

Several flight tests of the procedure have been conducted at Braunschweig-Wolfsburg airport. They required a detailed planning and briefing and had initially high demands on the equipment of the participating aircraft. The procedure was tested in a build-up approach in which the number of participating parties and the required complexity was increased incrementally. Initially simulator trials were conducted and evaluated. After that, flight trials with a single aircraft were conducted while a simulator on board was simulating the leading traffic. Lastly, flight trials with two different types of leading aircraft (King Air 350, Airbus A320) and a
trailing aircraft (Advanced Technologies Testing Aircraft System, ATTAS, VFW 614) were conducted.

The trajectories during the final trials had to be coordinated between the two aircraft and with air traffic control (ATC). The trailing aircraft (ATTAS), equipped with the in-house developed 4D FMS and autopilot, conducted approaches onto a simulated parallel runway.

As the airport offers only one concrete runway, an artificial ILS onto a parallel taxiway had to be created. This paper describes the different stages of the technical installations of the aircraft and presents the design, the build-up approach and the results of the conducted flight tests. In addition, the conducted safety briefings and the means to mitigate the risks during the trials are shown.