^{Figure 1: The location of the Stockholm Arlanda Airport (source: Å. Göransson, Neighbour relations at Stockholm Arlanda Airport, ANNA Conference, 2016-09-28/29)}

Stockholm Arlanda Airport is a three-runway airport (Figure 1) located in the Sigtuna Municipality of Sweden. It is the largest airport in Sweden and the third-largest airport in Scandinavia. In 2017 it carried approximately 27 million passengers.

Noise regulations

The airport has an environmental permit containing a number of terms regulating the airport’s activities. Among other terms it is regulated how the traffic should be handled when it comes to flight paths, use of runway combinations, noise levels, regulations, noise insulation, etc. The environmental permit has been determined in the environmental court.

Additionally, Stockholm Arlanda Airport annually compiles a Noise Management Plan (NMP), containing all activities regarding aircraft noise, highlighting on what the airport will work on during the year. The activities are spread over different departments of Swedavia, which is the airport owner.

^{Figure 2: Noise contours for Lden 55 dB(A) for Stockholm Arlanda Airport}

The case study focuses mainly on the operational procedures than could be implemented to reduce noise levels by having the aircraft fly at a higher altitude for a longer time when approaching the new runway. The case also includes a useful tool, the Virtual Community Noise Simulator (VCNS), in order to improve the impact of community engagement in the processes of decision making instead of presenting decisions once they are already made.

Objective

The objective of the case study is to test steeper glide approach angles in order for the aircraft to fly at a higher altitude and reduce the levels of noise over the communities. Two scenarios with different glide slope approaches were presented for the most commonly used type of aircraft.

Approach

The approach used in this case study included research, solution finding, testing and communication with the residents living at the south of the airport. Those communities are aligned with the new runway, close to the airport, but outside the L_den noise contour of 55 dB(A), which means they are out of the noise insulation conditions.

1. Newly built Runway 3 was constructed in 2003 and caused more residents to be exposed to the aircraft noise, thus, more noise complaints reached the airport’s management. The curved approach landing was selected as a solution to avoid the overflying above the communities, but after its approval,  the curved approach was not properly  used because of the requirement of special aircraft certification, special education of the crew, the requirement of particular weather conditions and limited usage time (curved approach couldn’t be used at peak times);
2. The airport admitted than only straight approach landing can be used at Runway 3, which made the communities living at the south of the airport angry and disappointed. It caused many discussions that took place in the legal court;
3. Research took place and new potential solutions were presented to alleviate the situation of communities being overflown by straight approach landing. Two new scenarios with different glide slope approaches were presented for the most commonly used type of aircraft, thus the aircraft should fly at the higher altitude for a longer time;
4. Testing of the potential solutions – Virtual Noise Community Simulator (VCNS) was set up to test the difference of noise between normal aircraft procedure and the one using steeper angle. The objective was to make sure that the community could feel the difference between the two procedures;
5. Communication with residents – the representatives of the communities were informed about the testing of the different options of landing and departure angles. Many people could actually hear the difference between the different approach angles which indicated that the VCNS scenarios could capture the change. The large number of participants indicated the public interest in participation and engagement in decision-making;
6. The communities have been involved in the process of decision making from the very beginning, so they were aware of the pros and cons related to each scenario.
    

The goal of applying the Virtual Noise Community Simulator (VCNS) for the community around Stockholm Arlanda Airport was meant to improve the public opinion about the airport. During a workshop for the residents living around the airport, the VCNS was applied to test whether people can perceive changes in the glide approach angle. It is difficult to say whether the case study was successful – not only the subjective perception but also the distrust of the residents played a role.

This case study reflects the importance of engaging with the community in the processes of decision making instead of presenting decisions once they are already made. Any change of the flight path or procedure will often not make the noise disappear but move it to another area. It is important that the people understand why a certain change has to happen and what the consequences and motivations were.