Less noise and better fuel efficiency during approach

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Impact on people and the environment: Approach to runway 14 at Zurich Airport. I
Impact on people and the environment: Approach to runway 14 at Zurich Airport. Image: Empa

The approach and landing of passenger jets is often a burden for people and the environment. The DYNCAT project, in which researchers are working with partners in Switzerland, Germany and France, is aiming at approaches that cause less noise and CO2 emissions - thanks to intelligent assistance systems for the pilots.

The approach to an airport runway is a real challenge for pilots: reducing speed, extending flaps and speed brakes and much more - all with as little noise and fuel consumption as possible. Moreover, air traffic control restricts the approach profile, and weather conditions are sometimes only vaguely known. In short, in addition to wind and other factors, the skills of the flight crew are a key factor in determining how well an approach meets all these requirements.

To optimize this process, the DYNCAT project led by the German Aerospace Center (DLR) aims at enabling environmentally friendly and more uniform flight profiles. Particularly during the approach, by helping pilots configure the airplane efficiently - and at the same time land in a fuel-efficient manner: This involves dissipating the jet’s potential and kinetic energy through aerodynamic drag, which in turn can be adjusted through the configuration of the airplane. Ideally, this means an approach without increasing thrust, which would add energy to the airplane - by using extra fuel - and generate more noise.

As part of the project, the team developed new on-board system functions that support pilots during the approach - with recommendations that pilots then choose to follow or ignore. These include optimized flap and landing gear settings to reduce noise and fuel consumption - finely tuned to the complex interaction of all factors and requirements.

To demonstrate the ability of these functions to reduce noise and CO2 emissions, simulator flights were conducted with experienced pilots at the Thales aviation group in Toulouse.

The approach target: Zurich Airport, runway 14. In the chosen situation, the air traffic controller instructed the pilots to take a lateral shortcut during the descent, which leads the airplane into a so-called over-energy condition.

This means that it has excessive potential and kinetic energy that must be dissipated during the approach to landing - but without creating unnecessary noise and consuming more fuel. This is a particularly difficult situation for pilots, where various strategies are possible.

About the project DYNCAT (short for: DYNamic Configuration Adjustment in the Terminal Manoeuvring Area) is a collaborative project with partners at the German Aerospace Center (DLR), Braunschweig site, the French THALES Group, the Swiss SkyLab Foundation, the Swiss International Air Lines and Empa. The project is funded by the SESAR Joint Undertaking under the EU's Horizon 2020 research and innovation program. DYNCAT started in mid-2020 and will run until the end of 2022.

Researchers from Empa’s Laboratory for Acoustics / Noise Control have illustrated the effects of the assistance system in a video (see below): It shows the acoustic impact of two comparable flights - one with the assistance of DYNCAT and a reference flight without. The aircraft noise model sonAIR, developed at Empa, calculated the noise level of the two flights on the ground - quantifying the benefits of the new system.

In general, the simulations and calculations showed that approaches using DYNCAT are quieter and consume less fuel. In the case of the two variants in the video, the "DYNCAT flight" consumed 55kg less fuel from the beginning of the descent and was up to four decibels quieter - a substantial relief. Despite high demands for climate-friendly and low-noise flying, some of which are contradictory, DYNCAT made it possible to achieve both goals more effectively.