^{Figure 1. The area around Barcelona Airport}

In 2018, Barcelona airport registered the record figure of 50,172,457 passengers (6.1% more than the previous year) and 335,651 operations and 172,940 tonnes of cargo. The airport is open 24 hours a day and can handle 90 operations per hour. Together with its two terminals, the airport can handle 55 million PAX/year. The airport is operated by AENA, the world's leading airport operator (by the number of passengers).

Noise regulations

The Balanced Approach was adapted to the Spanish legal code by the Royal Decree 1257/2003. Following this Royal Decree, the Resolution of 31 May 2011 of the Spanish Air Safety Agency (AESA) was published, introducing operating restrictions in El Prat Barcelona Airport, following the Balanced Approach procedure.

The Balanced Approach identifies the noise problem at a specific airport and analyses the measures available to reduce the noise, which can be classified into four principal elements – reduction of noise at source; land-use planning and management; noise abatement operational procedures; operating restrictions. Operational restrictions will be applied as the last option only when all the rest of the measures cannot reach the noise objective.

This case study is framed in the previous regulation, directive 2002/30/EC, before the new Regulation 598/2014 came into force in June 2016.

This case study analyses how to implement operating restrictions while the previous regulation was in force (until 2016). The impact on airlines, airports, passengers and local economies, together with the noise benefits, must be assessed before the implementation process. In this case, the operating restrictions are applied to a group of aircraft based on individual noise performance.

Objective

The objective was to improve the noise environment around Barcelona airport by reducing the maximum noise levels (L_max), which are usually produced by the oldest (noisiest) aircraft flights during the day (annoyance) and during the night (awakeness).

Approach

This case study's approach was to prepare a detailed report following the Balanced Approach methodology described in the Directive 2002/30/EC and the Spanish legal code, the Royal Decree 1257/2003 to assess the cost/benefit analysis for the implementation of operating restrictions in Barcelona Airport.

1. The process started with a detailed study and a comprehensive examination of the current inventory of measures, noise and objectives and the expected evolution with several scenarios, the assessment of new measures and the conclusions;

2. Considering the acoustical description, modelling and indicators, the study was searching for the benefits of operating restrictions and characterised the global noise in terms of number of people exposed and exposed areas to each L_den and L_night levels (Figure 2);

^{Figure 2. Areas and the number of people affected by aircraft noise}

3. In-depth analysis of marginally compliant hour-by-hour operations at Barcelona Airport was performed to characterise the noise from the noisiest aircraft with its influence on general noise;

4. After an in-depth study of the current situation, it was necessary to characterise the future and answer the questions on what would happen to the airport's development in the next 5-7 years, which is the noise action programme, which are the fleets, etc.;

5. The most important part of the study was the assessment of "additional" measures. Firstly, the measures were defined (operational restriction measures) and assessed from an acoustic point of view. Finally, a cost-benefit analysis was carried out;

6. The acoustic assessment of the additional measures was carried out for three different scenarios of implementation, always comparing noise contours with and without marginally compliant aircraft in terms of L_denand L_night and areas and people exposed to each level (see one scenario in Figure 3; download the full study for the three scenarios). The results were not enough to implement a particular measure (restriction), and the study was complemented with in-depth analysis in some selected points with more populated areas;

^{Figure 3. One of three scenarios comparing noise contours with and without marginally compliant aircraft in terms of L_den and areas and people exposed to each level (download the full study for other scenarios)}

7. The outcomes of this final assessment showed clear benefits in terms of the number of people affected by noise annoyance (under noise insulated levels) and less awakeness due to the aircraft noise;

8. The cost/benefit analysis showed only one airline affected at significant levels;

9. The study was first presented to the GTTR and after its approval started the legal process to implement the operating restrictions. The restrictions were approved by the Resolution of 31 May 2011 of the Spanish Air Safety Agency (AESA);

10. The implementation process has been observed and controlled by the aviation authorities.

Assessment of different scenarios with and without marginally compliant aircraft, in terms of L_den and L_night and areas and people exposed to each level were not enough to implement a restriction, and the study had to select some points in more populated areas to be analysed more deeply in terms of L_Amax (and frequency) and in terms of the noise energy contribution of each aircraft type into L_den and L_night in those points.

However, the final report showed clear benefits in terms of the number of people affected by noise annoyance (under noise insulation levels) and less awakeness due to aircraft noise during the night period.

The lack of noise data certificates from some airlines was solved during the hearing procedures. In general, during the implementation process, most airlines understood the measures and did their best to re-schedule aircraft (other times, the airlines offered other less noisy aircraft). Nevertheless, observation and control are needed to follow the infringements successfully.