Flyover Noise Measurements of a Spiraling Noise Abatement Approach Procedure

Kurzfassung

DLR is investigating alternative low-noise approach procedures. 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, i. e. in direct vicinity of the airport. Ground noise levels along the entire flight path prior to the helix are significantly reduced. The effectiveness of this procedure, referred to as Helical Noise Abatement Procedure (HeNAP), 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 DLR autopilot especially capable of tracking curved flight path trajectories was flight tested. Three HeNAPs were included in the flight plan, as well as standard and steep landing approaches. In addition, dedicated fly-over noise measurements were organized, supported by RWTH Aachen University. Twelve ground microphones have been installed along the common approach path and the helical flight segment. Despite adverse wind conditions at the only available test day, the measured data confirm the predicted noise dislocation effects. High noise levels have been limited to observer locations around the helix. DLR noise prediction methods 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 R&D member of DFS to study the impact of spiraling procedures on ATM integration and air traffic controller workload, e. g. 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 highly frequented airports. The operational and economic environment still need more detailed investigation. Helical approaches become more feasible for implementation at small, low-frequented regional airports or during night hours to avoid possible noise related curfews.