Customer

Gatwick Airport Ltd

Context

Aircraft noise is an issue for almost all major airports around the world; community reaction to and perception of aircraft noise is a complex matter which requires consideration of multiple factors. Gatwick Airport Ltd (GAL) is no different. For a physically small country with a large demand for aviation activity, the UK airspace infrastructure is a scarce resource. England has one of the highest population densities in the EU and so it’s no surprise that aircraft noise will be a particular issue here. As the demand for air traffic increases and the airspace becomes saturated, it is becoming increasingly important to balance the environmental impacts of aviation with the economic benefits air travel brings to a country.

Back in August 2015, GAL commissioned an Independent Arrivals Review to see what could be done to better manage noise around the airport. This review sought to consider whether: a) Everything that could reasonably be done to alleviate the problems which local communities were raising was in fact being done; and b) The mechanisms adopted by GAL for providing information to the local community and for handling complaints were fully adequate for the task. The Arrivals Review, published in January 2016, recommended 23 specific steps to improve the management and mitigation of noise from arriving aircraft, and for better community engagement by GAL.

The Arrivals Review led to the creation of a Noise Management Board (NMB), designed to enable better accountability for and coordination of noise strategies and provide a transparent process for regular review and update on noise reducing initiatives. The NMB comprised representatives from industry, local communities and the airport, led by an independent chairperson, and supported by technical advisors. In 2016, GAL commissioned us to provide project management support and technical assistance with the implementation of recommended initiatives.

Role of Egis

We have supported a programme of work on behalf of GAL since the NMB’s inception and worked closely with the airport in helping to achieve its ultimate goal; to reduce the impact of aviation noise on communities around Gatwick.

GAL adopted ICAO’s Balanced Approach[1] to aircraft noise mitigation across four areas as indicated below. Focus on improving transparency of key information for local communities and industry was also prioritised by GAL, to strengthen community trust and build a better relationship with its neighbours.

Over the years we’ve provided technical support to the NMB and attended NMB meetings, public meetings and workshops in an advisory role, presenting information papers and reports on the studies progressed on behalf of GAL and the NMB. We also led a number of projects to incentivise and improve the noise environment around the airport covering arrivals, departures, monitoring and reporting activities.

Arrivals

1 – Change to the measurement of Continuous Descent Approach (CDA) performance

CDA, also known as Continuous Descent Operation (CDO), is a method by which aircraft approach airports prior to landing. It is designed to reduce fuel consumption and noise compared to other conventional descents. Instead of approaching an airport in a step-like fashion, stepping down to each new (lower) altitude, CDO allows for a smooth, constant-angle descent to landing. The principle of a CDA is illustrated in the diagram below.

We managed a change to the measurement of CDA performance at GAL. This involved raising the altitude at which monitoring of the CDA procedure commenced to help reduce the impact of aircraft at higher altitudes on local communities.

2 – Change to the Instrument Landing System (ILS) joining point procedures

The move of the ILS minimum join from 10NM to 8NM was a recommendation of the Gatwick Arrivals Review. In 2016, we project managed a change to NATS vectoring procedures to re-establish the ILS joining point on final approach, from 10NM to 8NM from runway end. The intention of this change was to redistribute the pattern of arriving aircraft to replicate as close as possible the pre-2013 traffic distribution.

3 – Investigation of a runway alternation protocol

We investigated the use of a runway alternation protocol to switch runway ends during periods of low wind. The aim was to provide respite to residents that sometimes were affected by long periods of westerly operations. Analysis of weather data showed that a protocol could be implemented for approximately 20 days per year and the necessary procedures and safety arguments were developed. The protocol did not proceed due to objections from communities who felt they would have been adversely affected by it.

4 – Review of commercial flight information

Our team undertook a review of the information provided by commercial flight planning service providers to airlines operating at Gatwick. The review found that there were discrepancies in the information provided to different airlines, for example, incorrect statements on the noise abatement procedures. The review included a gap-analysis against the information provided in the UK AIP. On completion of the review, we co-ordinated with flight planning service providers to ensure the information was updated.

5 – Gatwick operator briefing pack

Through engagement with operators, it was identified that some airlines operating infrequently at the airport were not familiar with all the required noise abatement procedures at the airport. As such, it was agreed that a summary of key information from Gatwick’s AIP would be useful to ensure that both new and frequent flyers at the airport had easy access to important operational and noise abatement information at the airport.

Through significant consultation with GAL and airlines, we developed a briefing pack for operators at GAL that covered all aspects of airspace and airfield operations. In addition to noise abatement procedures, it included information on Airport-Collaborative Decision Making (A-CDM) procedures, minimising runway occupancy, procedures for using the northern runway, and a number of other operational topics.

6 – Reduced night noise trial

We have supported preparations for a trial to assess the extent to which Performance Based Navigation (PBN) can deliver noise benefits to arriving aircraft during the night, by reducing the number of noisy ‘outliers’ that are significantly lower or noisier than most aircraft. This activity was initiated in 2017 and has been planned in accordance with the UK CAA’s CAP1616 guidance.

Significant engagement and industry consultation took place through 2018/2019, and we undertook detailed data and noise analysis to demonstrate the expected noise benefits of the trial. On behalf of GAL, we prepared and submitted the Trial Submission Pack in September 2019, comprising details of the trial engagement, industry consultation, Instrument Flight Procedure (IFP) designs, environmental and safety assessments, trial procedures and activity timescales. This information is published on the CAA Portal. GAL is awaiting a clear indication of likely timescales for assessment of the RNN trial by the CAA, before progressing with trial implementation. 

7 – Low noise arrivals metric study

In 2017, the NMB led the way in establishing a national cross-industry project in the UK to develop a new Low Noise Arrivals Metric. It aimed to complement the current CDA definition and the effectiveness of the CDA procedure in reducing noise, as well as providing an additional performance target for Gatwick which could also be used at other airports. The new metric would enable the measurement and benchmarking of arrivals against a viable optimum low noise approach. This Future Airspace Strategy (FAS) sponsored initiative was progressed at the request of the NMB and via GAL by the CAA’s Environmental Research Consultancy Department and NATS throughout 2018/2019. Our team provided project management support and supported the development of a CAA CAP document. The schematic below illustrates the three newly proposed noise categories, A, B and C. These represent different profiles with different noise performance.

In 2020, on behalf of GAL, we validated the new metric using Python and PowerBi to demonstrate that the proposed Cat A profile was quieter than Cat B and Cat C for a range of aircraft types. Detailed analysis using historic track and noise data was undertaken, comprising a thorough noise assessment of the arrival profiles in a range of real-world conditions. The validation concluded that the noise categories proposed by the CAA were correct; Cat A aircraft were quieter than Cat B aircraft, which were quieter than Cat C aircraft.

8 – Airline noise league table

An Airline League Table or Fly Quiet Programme is an initiative to encourage airlines to adopt the quietest fleet and fly them in the quietest way possible. The initiative is designed to encourage airlines to reduce their noise impact by continually improving their operation and fleet. The programme involves evaluating noise performance using a set of metrics and reporting the results publicly to incentivise good practice by airlines. The qualification criteria, metrics used, and method of reporting Airline League Tables/Fly Quiet Programme results vary between different airports.

For GAL, we developed an Airline Noise League Table, commencing with a review of international best practice of Fly Quiet programmes. A number of options were presented to GAL for consideration. In collaboration with GAL and airlines, operational and strategic metrics were identified for inclusion in the table, including CDA performance (arrivals), track keeping performance (departures) and Quota Count (QC) per number of seats.

We designed a proficient tool and used historic flight data to validate the different functions and to test different weighting and scoring combinations. The league table was adopted by GAL, who have subsequently integrated the tool into their regular reporting processes.

Departures

1 – Noise Abatement Departure Procedures (NADP)

NADP is a noise abatement procedure which reduces the amount of noise on the ground during aircraft departure. There are two commonly used procedures; NADP 1 and NADP 2.

  • NADP 1 reduces noise around and over the departure end of a runway; the main objective of this procedure is to gain height as a priority over forward acceleration;
  • NADP 2 reduces noise over the areas more distant from the runway end; this procedure prioritises increasing forward speed over height gain.

The diagram below illustrates altitude profiles comparing NADP 1 and NADP 2 procedures:

We analysed the noise benefits of NADP 1 vs NADP 2 for local communities around Gatwick. The work involved gathering the details of the current situation and analysing the impact of recommending one or other of the procedures. The study found that consistent use of NADP 2 would reduce numbers of people affected by noise around the airport compared to NADP 1.

A UK CAA ANMAC report, published in July 2018, identified that the noise benefit of one NADP procedure over the other is barely noticeable to the human ear, typically between 1 and 3dB, and that a change in NADP simply moves noise from one location to another. The study concluded that there would not be a significant noise benefit from the standardisation of NADP procedures at UK airports. Coupled with this, the safety implications associated with enforcing the use of one procedure over another at the airport meant that continued use of preferential procedures was encouraged for airlines.

2 – Review of Gatwick Airport departure noise limits

We undertook a review of the departure noise limits at which GAL levy fines, with the objective of proposing new, stricter noise limits to encourage the noisiest aircraft to fly more quietly. The existing noise limits and fine amounts were evaluated, and detailed analysis was undertaken to establish a new regime whilst considering the findings from a benchmarking study which reviewed charging schemes at comparator airports. Based on the findings of the review and analysis, we proposed an alternative charging regime based on Quota Count. The proposal is currently under evaluation by GAL and DfT.

3 – Continuous Climb Operation (CCO) noise study

During the COVID-19 pandemic in 2020/2021, traffic levels at Gatwick Airport dropped significantly and the requirement for departing aircraft to fly extended level segments diminished because the airspace in the south of the UK was much less busy. In early 2020, more aircraft were able to climb to 7,000ft unimpeded. GAL commissioned a study to investigate the environmental noise impact of the change in departure climb profiles.

We analysed the climb performance of departing aircraft on all GAL SIDs using Python and PowerBi to understand how departure profiles changed when traffic levels diminished. Detailed noise analysis was performed on selected routes to compare the noise impact of CCO and non-CCO departures for a range of aircraft types.

Monitoring & Reporting

1 – Fair and equitable distribution

In 2017, the NMB set out to achieve a Fair and Equitable Distribution (FED) of arrivals at the airport. As part of this initiative, regular monitoring and reporting of traffic within the arrival swath was essential to observe any changes in traffic distribution. We were responsible for performing this FED assessment, undertaking detailed Gate analysis which monitored arrivals to the East and West of the airport. Vertical and lateral distributions, heatmaps, and density plots over each gate were analysed and assessed to understand if any changes to the traffic distribution had occurred in the monitoring period. The results of the analysis were reported regularly to the NMB through detailed FED reports.

2 – Automation of GAL noise reporting

We undertook a detailed review of existing noise reports produced by GAL to identify obsolete material and improve and simplify the existing structure and report content. This involved comparing GAL’s noise report with noise reports at other airports to identify best practice and areas for improvement. A new report template was developed for GAL based on the findings of the review.

Our team went on to develop an intelligent tool which automatically created graphs and charts for the new report template using data taken from GAL’s Airport Noise and Operations Monitoring System (ANOMS) as well as other data sources. This process aimed to reduce workload internally and to streamline the noise reporting process.

3 – Noise communications and engagement benchmarking study

As part of GAL’s strategy and commitment to achieving sustainable growth, a number of obligations and actions were agreed with local authorities to ensure measures are in place to minimise as far as possible any short- and long-term impacts of growth. As required by their Noise Management Action Plan (2015-2018), GAL committed to undertake a benchmarking study to review their performance on operational noise management and communications against comparator airports.

On behalf of GAL, we undertook a benchmarking study which compared GAL’s noise communication and engagement practises against a number of UK, European and international airports in four areas of noise management: noise complaints; community outreach mechanisms; noise metrics and reporting; and noise ombudsman. The review concluded that GAL performed well in many of the benchmarked categories compared to other airports and also identified some areas for improvement.

Results

Since the inception of the NMB, a lot of hard work, time and effort from all those involved has contributed positively to the impact of aviation noise at GAL. This is demonstrated in maps produced by the CAA showing ‘noise contours’ which measure the change in total noise at an airport over time. These contours illustrate the accumulated impact of initiatives designed to reduce aviation noise.

The table[1] below demonstrates the change in noise contour area at GAL from 2016 to 2018. As illustrated, all contour areas have reduced over time, with bigger reductions observed in contours further from the airport, i.e. the 57dB contour has reduced by 12% from 2016 to 2019.

Leq (dBA)2016 Area (km2)2017 Area (km2)2018 Area (km2)2019 Area (km2)
>5744.242.640.038.7
>6025.124.123.222.4
>6313.713.413.112.6
>667.27.16.96.7
>693.83.73.63.5
>722.12.12.01.9

Since 2016, the noise contours at GAL have continued to decrease, reducing areas exposed to aircraft noise on the ground. Today, we continue to work with GAL to help reduce the environmental impact of aviation noise on communities around the airport.


[1] http://www.icao.int/environmental-protection/Pages/noise.aspx

[2] Figures taken from Gatwick Airport Noise Reports – https://www.gatwickairport.com/business-community/aircraft-noise-airspace/noise-reports/

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Katie Baker

Katie Baker

Senior Consultant

+44 1252 451 651