September 22, 2016

Less aircraft noise and lower fuel consumption – three days of test flights in Frankfurt with the DLR ATRA research aircraft for a new active noise abatement project

Reducing aircraft noise over residential areas while saving kerosene – this dual improvement is the aim of a joint research project being conducted by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) and the Umwelt- und Nachbarschaftshaus (UNH) in Kelsterbach. During three days, from 26 to 28 September, DLR, using its A320 Advanced Technology Research Aircraft (ATRA) will be testing the Low Noise Augmentation System (LNAS), a pilot assistance system for noise-optimised landing approaches.

Deploying the landing gear and flaps more quietly

During landing – generally the most labour-intensive phase of a flight – it is often difficult for pilots to select the optimum times at which to extend the flaps and lower the landing gear so that the greatest possible part of the landing approach can be conducted in quiet, fuel-efficient circumstances, with the engines at idle. As a result of a doctoral research project at the DLR Institute of Flight Systems in Braunschweig, an assistance system has been developed that shows the pilots a flight deck display of the points at which they need to carry out certain actions to create the optimum low-noise descent in line with the approach controller's instructions. To date, the system has been successfully tested in a simulator and in initial research flights with no surrounding air traffic. Now it is time for the real test, during the peak period at Frankfurt Airport.

Weather conditions, poor visibility, the weight of the aircraft and instructions from air traffic control each have a different effect on every landing. DLR researchers want to find out how these variable influences affect the new assistance system and how professional pilots respond to the system. For this reason, pilots from several airlines have taken turns to sit alongside a DLR test pilot on ATRA's flight deck and make approach flights to Frankfurt – sometimes with the assistance system, sometimes without. The test flights are being coordinated with the German air traffic control service (Deutsche Flugsicherung; DFS) and Frankfurt Airport. Before the actual flight tests, extensive trials were carried out in the DLR Air VEhicle Simulator (AVES). "We are delighted to now be able to send the newly-developed assistance system for a real-life check at the busiest airport in Germany," says Stefan Levedag, Head of the DLR Institute of Flight Systems. "An important step in the development process is gathering the impressions and experiences of experienced airline pilots with the new system in the demanding operational environment at Frankfurt Airport, with its high volume of traffic." Another advantage is the numerous noise measurement stations that have been set up around the airport. These can be used to locally quantify the noise reduction effect of the optimised approaches.

Umwelthaus providing 560,000 euros for the research project

The UNH is supporting the project with a total of 560,000 euros. Improving the noise situation for the Rhine-Main region through active noise abatement is a top priority for the Airport and Regional Forum (Forum Flughafen und Region; FFR). "In collaboration with DLR, we have succeeded in continually advancing new, innovative processes. The LNAS project has a very special appeal because it enables noise to be reduced and kerosene to be saved at the same time," says Günter Lanz, Managing Director of UNH. "In addition to processing data and carrying out monitoring, the main purpose of our work is to commission scientific studies and research projects and thus fill factual and expertise gaps. Hence, we want to provide new impetus for the debate concerning aircraft noise and give innovative ideas a chance." The results of the project will be presented at the 4th ICANA 2016, the International Conference on Active Noise Abatement, in November 2016 and subsequently published.

AG Perspektive (a working group of the FFR expert panel on active noise abatement) is providing expert guidance for the project. Representatives of the aviation industry are working with public authorities and representatives of local councils, DLR and the Aircraft Noise Commission on active noise abatement measures that have a prospect of being implemented in the medium to long term. "The research project is an excellent complement to FFR's previous work," explains Anke Giesen, Board Member of Fraport AG and of the Airport and Regional Forum.

Test flight programme

The programme includes a total of five test flights of five hours per day, including take-off, approach and go-around using the northwest runway at Frankfurt Airport. During each test flight, the flight captain – a DLR pilot – will be accompanied by four pilots who will each carry out two approaches in normal operational conditions – once with and once without the pilot assistance system. The sequence of pilots and use of the system has been arranged so that any learning effect is excluded.

Investigations and expectations

In the test flights, the altitude and speed profiles of conventional approach flights will be investigated in terms of their potential for reducing noise, fuel consumption and flight time within the constraints of real flight operations.

In addition to improvements in terms of noise and precision, error-free functioning of the prototype in actual flight operation is expected from the start. At the same time, a high level of acceptance by the pilots is sought.

Background information

LNAS assistance system

The LNAS assistance system consists of the preliminary path planning, runtime correction and energy-based display components. From the data available for the A320 ATRA, a simplified simulation model is generated for the preliminary path planning of an ideal vertical approach profile. This ideal vertical approach profile includes optimum points for deploying the flaps and landing gear, and speed setpoints. If the pilot carries out manoeuvres in line with the guidelines, the approach from cruising altitude to the stabilisation height can be carried out with minimal thrust (engines at flight idle). At the time of this planning, the aircraft will ideally be just about to start the approach. At this point, only the wind information at the current position of the aircraft and on the ground is available. This means that all intermediate values can initially only be interpolated from these two values, as the precise wind profile is still not known. Via an appropriate Human Machine Interface, the pilots can see the altitude profile and, especially, the precalculated speed changes in the form of energy levels, as well as the individual action points shown as symbols.

During the approach, the actual wind values are recorded at each new altitude, and these are used to improve the wind profile for the entire approach. In the event of possible lapses on the part of the pilots (carrying out an action too early or too late) or instructions from the approach controllers, the ideal sequence of actions needs to be constantly adapted. The runtime correction component of the system carries out these adjustments by making corresponding shifts in the individual action timings. In doing so, the optimisation goals for the adjustments are always adherence to the stabilisation conditions at the 1000-foot gate, the lowest possible engine speed and the complete avoidance of spoiler deployment.

Airbus A320-232 D-ATRA

The Airbus A320-232 'D-ATRA', the latest - and largest - addition to the fleet, was deployed by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) in late 2008. ATRA (Advanced Technology Research Aircraft) is a modern and flexible flight test platform which sets a new benchmark for flying test beds in European aerospace research - and not just because of its size.

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Falk Dambowsky

Head of Media Relations, Editor
German Aerospace Center (DLR)
Corporate Communications
Linder Höhe, 51147 Cologne
Tel: +49 2203 601-3959

Stefan Levedag

German Aerospace Center (DLR)
Institute of Flight Systems
Lilienthalplatz 7, 38108 Braunschweig

Oliver Brieger

Head Flight Experiments
German Aerospace Center (DLR)
Flight Experiments
Lilienthalplatz 7, 38108 Braunschweig

Günter Lanz

Umwelt- und Nachbarschaftshaus (UNH)