Trials for quiet and efficient flights in advanced continuous descent approach using the low-noise augmentation system LNAS

Abstract The pilot assistance system Low-Noise Augmentation System (LNAS) developed by DLR has already been demonstrated, tested, and used in real air traffic in various projects. The work described in this paper was aimed at extending LNAS to alternative approach procedures in the project LNAS-CGN. For this purpose, flight simulator tests were conducted with the scenery of Cologne Bonn Airport (three letter code CGN). The aircraft used was an Airbus A320. The participating pilots were airline pilots who had not yet gained any experience with the LNAS system. LNAS optimizes the vertical profile of the approach from the beginning of the descent (top of descent) to the stabilization height at 1000 ft above ground so that the aircraft can be flown with the minimum thrust, the minimum noise emission, as well as minimum fuel consumption with a given lateral route. In doing so, the system continuously corrects the trajectory ahead, depending on the constraints created by air traffic control instructions or changing weather conditions. The system provides guidance on which airspeed, aircraft configuration and controller modes are most favorable for the approach and provides the cockpit crew with the timing for subsequent actions. In particular, the so-called Advanced Continuous Descent Approach (ACDA) was considered during this project. This is an approach in which the descent is initiated comparatively late and is therefore steeper than for other types of approaches. The aircraft's energy management is of great importance here, especially since the use of speed brakes should be avoided for reasons of noise abatement. More than 150 approaches were carried out, in which the system was either used or not. The pilots were interviewed afterward about their experiences. Thereby the focus was on the flyability of the approach itself and the workload in the cockpit with and without support from the system. In addition, the flight tests were evaluated with regard to their fuel efficiency, configuration management, and influence on the aircraft noise generated. The feedback from the cockpit crews was positive. LNAS was appreciated for pilot support while performing steep approaches, especially with regard to the augmentation of pilot’s awareness about the current aircraft energy level. It could be shown that with the help of LNAS even in unconventional ACDA’s, the mean fuel consumption can be reduced and the application rate of speedbrakes can be reduced significantly.