Flyover Noise Measurements of a Spiraling Noise Abatement Approach Procedure

Abstract

Alternative approach procedures are currently under investigation to evaluate their ground noise reduction potential. One such procedure involves approaching the airport at a considerably higher altitude compared with standard landing trajectories, followed by a spiraling descent (helix flight path) shortly before the runway threshold. In this way, high ground noise levels by approaching aircraft are dislocated away from the common approach path and concentrated in the area near the helix path, that is, in direct vicinity of the airport. Ground noise levels along the entire flight path before the helix are significantly reduced. The effectiveness of this procedure, referred to as “helical noise abatement procedure,” has been quantified by means of computational simulation analyses. These analyses also focused on aspects such as increased fuel burn and the occurrence of multiple noise events below the helix. In June 2009, a new autopilot by the DLR, German Aerospace Center, especially capable of tracking curved flight-path trajectories, was flight tested. Three helical noise abatement procedures were included in the flight plan, as well as standard and steep landing approaches. In addition, dedicated flyover noise measurements were organized. Twelve ground microphones were placed along the common approach path and the helical flight segment. The measured data confirm the predicted noise dislocation effects. High noise levels were found to be limited to observer locations around the helix. Results from computational noise prediction have been compared with the experimental data. Predicted trends and noise dislocation effects are in good agreement with the measurements, whereas the absolute numerical values show discrepancies. The flight test was closely accompanied by a research and development member of the German air navigation service provider DFS Deutsche Flugsicherung GmbH to study the impact of spiraling procedures on air traffic management integration aspects and air traffic controller workload, for example, increased interaction with the pilots. Obviously, a spiraling approach procedure would not be implemented into the existing air traffic scenario with its common approach paths and more frequented airports. The operational and economic environment still need more detailed investigation. Helical approaches become more feasible for implementation at small, less-frequented regional airports or during night hours to avoid possible noise related curfews.