A package of measures and support tools.
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.
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 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
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.