The impact of changing fleet makeup on airline noise emission

Karina Einicke 1

John Kennedy 2

Trinity College Dublin, the University of Dublin College Green Dublin 2 D02 PN40 Ireland

ABSTRACT With the advent of the Environmental Noise Directive (END) population-level modeling of exposure to aircraft noise has increased within Europe. Present noise exposure legislation focuses on airports whereas the greatest potential to implement noise reduction technologies lies with the airlines and aircraft manufacturers. This work focuses on modeling the noise emission of the fleet of Europe’s largest airline by passenger numbers, Ryanair. The potential for noise reduction through fleet level decisions will be evaluated and the impact of changing fleet makeup assessed. The airline’s current fleet consists of 409 Boeing 737-800 aircraft and 29 Airbus A320-232 aircraft, while 210 new Boeing 737-8200 aircraft are on order. The new aircraft has a 60 % smaller footprint in the 85 dB(A) noise contour during take-o ff than the existing 737-800. The 85 dB(A) contour of 737-800 extends to around 4 . 5 km along the runway, while the contour of 737-8200 is reduced to ca. 2 . 5 km . This is achieved by implementing a new winglet design and more e ffi cient power units, which operate with lower fuel consumption (and thus lower aircraft weight), fewer carbon emissions, and lower noise emissions. The impact of this change on the fleet level noise emission is evaluated through a case study of departure operations at Dublin Airport. Noise contours generated with SoundPLAN show the noise e ff ects of the di ff erent aircraft types of the current and future Ryanair fleet under realistic operating conditions. It was shown that in a scenario where Ryanair switched its aircraft at Dublin Airport to the 737-8200, the area in which noise from departure exceeds the 55 dB(A) day time threshold could be reduced by over 25 % .This would lead to a beneficial change for 10,000 residents in the current > 55 dB(A) area around Dublin Airport. The generated noise contours provide an evidence base for decision making within the airline for investments aiming to reduce noise levels around airports and meet sustainability targets.

1 EINICKEK@tcd.ie

2 JKENNED5@tcd.ie

a slaty. inter.noise 21-24 AUGUST SCOTTISH EVENT CAMPUS O ¥, ? GLASGOW

1. INTRODUCTION

Air tra ffi c has been increasing and will further grow in the future. This causes a rise in aircraft emissions, which also include noise emissions. Noise can cause negative health e ff ects, such as annoyance [1], sleep disturbance [2], and negative impacts on the cardiovascular and metabolic systems [3–5]. The WHO estimates the burden of environmental noise in DALYs (disability-adjusted life-years), which includes 61,000 years for ischemic heart disease and 45,000 years for cognitive impairment in children in western European countries. In addition, it also lists 903,000 years for sleep disturbance, 22,000 years for tinnitus, and 654,000 years for annoyance caused by noise. [6] Noise limits at airports are introduced to reduce aircraft noise and improve life quality. In this study Dublin Airport was chosen as it is a key airport for the airline. Noise emission at Dublin Airport is currently assessed in terms of night and day time noise limits. During the night (23:00-07:00) the number of flights is limited to not disturb the residents surrounding the Dublin Airport area. The airport has a noise budget, which limits the emitted aircraft noise and thereby limits the air tra ffi c. Therefore, the quieter the aircraft departing from and arriving at an airport, the more air tra ffi c is possible. Noise charges are established for each aircraft movement. The noise charge depends on the aircraft’s category. [7,8] Aircraft in Europe are categorized into chapters, depending on their noise emission, maximum take-o ff mass, and aircraft type. In 2020 94 . 3 % of aircraft at Dublin airport were chapter 4 classification or better [9]. This includes around 40 . 4 % of Boeing 737-800 aircraft. At Dublin Airport noise preferential routes and runway are already in operation to reduce the noise impact on areas surrounding the airport. [10] Improving the aircraft design can lead to significant noise reduction in aircraft noise. Thus modern aircraft are quieter. Retrofitting aircraft technology to reduce noise is another option. Noise reduction technology such as acoustic liners, landing gear hub caps, and new winglet designs can be added to existing aircraft [7,11]. Departures at Dublin Airport are modeled in a 24 h window with SoundPLAN. The future Ryanair aircraft, the 737-8200, is integrated into the fleet at Dublin Airport and noise footprint changes are evaluated.

Table 1: Ryanair fleet makeup from [12,13]

Aircraft Type Current On-order Historic Seats

ATR 42 / 72 4 78

Airbus A320 29 5 150

Airbus A321 4 212

BAC 1-11 16 59

Boeing 737-200 21 119

Boeing 737-300 4 149

Boeing 737-400 1 188

Boeing 737-700 1 143

Boeing 737-800 409 127 189

Boeing 737-8200 61 149 197

Total 500 149 182 -

2. RYANAIR FLEET

Ryanair’s fleet mainly consists of Boeing 737-800 aircraft. According to Ryanair [13] 210 Gamechanger aircraft (Boeing 737-8200) have been ordered. The new aircraft will have reduced fuel consumption, and less carbon and noise emissions. [13] Table 1 shows the development of Ryanair’s fleet. In the past years, Ryanair’s fleet did not only grow but also reduced its noise emissions through the uptake of state of the art aircraft. Figure 1 displays a selection of maximum departure noise contours at L Amax = 85 dB(A) of former, current and future Ryanair aircraft. While the ATR42 / 72 aircraft has the smallest L Amax = 85 dB(A) and stretches 2 km along the runway, it can only host 78 passengers. The Airbus 320-211 can accompany 150 passengers and its L Amax = 85 dB(A) contour propagates 3 . 5 km along the runway. While the Boeing 737-800 L Amax = 85 dB(A) departure footprint is significantly larger with over 4 km, it can transport 189 passengers. The future Ryanair aircraft, the Boeing 737-8200, can accompany 197 passengers and its L Amax = 85 dB(A) contour is reduced to under 2 . 5 km. BAC 1-11 has a 147 % larger 85 dB(A) noise contour than the Boeing 737-800. An even more impressive improvement is the comparison between the Boeing 737-200 and Boeing 737-800, the 85 dB(A) contour noise footprint was reduced by over 500 %. With introducing the Boeing 737-8200, Ryanair commits to an aircraft, which has over 60 % less noise emission at L Amax = 85 dB(A) than the Boeing 737-800 during take-o ff .

Figure 1: Departure noise comparison of historic and future Ryanair aircraft, noise contour at L Amax = 85 dB(A)

3. DUBLIN AIRPORT DEPARTURE ROUTES

Dublin Airport has two operating runways and one runway under construction. The south runway ( 10R / 28L ) operates easterly and westerly arrivals and departures. Runway 16 / 35 operates north- westerly and south-easterly arrivals and departures. The north runway ( 10L / 28R ) is currently still under construction. It is located parallel to the south runway and will operate in mixed or segregated mode along with the south runway. Dublin airport limits noise emissions by limitation on reverse thrust and preferred runway usage. In addition, environmental corridors and departure procedures are in place. Reverse thrust during landing operations is prohibited on any runway between 23:00-06:00 (except for operational or safety reasons). Between 20:00-07:00 engine test runs are not permitted, to limit noise exposure for surrounding areas. [9,10]

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This study focuses on one day of operation at Dublin Airport, including real values for aircraft operations and routes. On the 9th of March 2022 Ryanair flights made up almost 40 % of all departures from Dublin Airport. Table 3 gives an overview of aircraft types departing from Dublin Airport. Ryanair flights made up 89 out of 225 in total. Table 2 displays how many aircraft departed on which trajectory from Dublin Airport. During day-evening time (07:00-23:00) 210 aircraft departed in total. Ryanair departures during day-evening time made up 78 Boeing 737-800. Within the night time period (23:00-07:00) only 15 aircraft departed from Dublin Airport, 11 of which were Ryanair aircraft. On that day Ryanair operated mainly Boeing 737-800 aircraft at Dublin Airport, making it an ideal case study for the impact of a complete change to a next generation aircraft configuration. Residential areas surrounding Dublin Airport have a day-evening noise limit of 55 dB(A). The night time limit is set at 50 dB. Furthermore, in simulations an evening 3 penalty of 5 dB(A) and a night time penalty of 10 dB(A) is applied in the calculation. [14]

Figure 2: Dublin Airport departure noise map for day and evening time (07:00-23:00), no evening time noise penalty applied. Each route is indexed from 1 to 18.

Dublin Airport was modeled for a 24 h window (09 / 03 / 2022) in Figure 2. To simplify comparison after later departure aircraft modification the evening time is joined with the day time and no penalty is applied. Flights and departure routes were approximately tracked via the flight tracking website FlightAware [15]. Departure flight trajectories were condensed into 18 di ff erent departure routes from Dublin Airport on 09 / 03 / 2022. The numbered flight trajectories from table 2 corresponds to the departure routes seen in Figure 2. Aircraft types labeled as other in table 3 were assumed to be Boeing 737-800.

3 The evening time is set as 19:00-23:00.

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Table 2: Dublin Airport number of departure flights per trajectory on 09 / 03 / 2022, data from FlightAware [15]

Number of

Number of

Departure

Ryanair Departures

total Departures day night total day night total

Trajectory

1 5 5 8 8

2 23 23 26 26

3 3 3 4 4

4 19 4 23 49 4 53

5 4 4 8 12 6 18

6 3 1 4 12 1 13

7 2 1 3 6 1 7

8 8 8 13 13

9 1 1 2 2 2 4

10 6 6 14 14

11 3 3 9 9

12 0 4 4

13 0 9 9

14 0 4 4

15 0 30 30 16 0 4 4

17 0 2 1 3

18 1 1 2 2

total 78 11 89 210 15 225

Table 3: Dublin Airport departure aircraft types on 09 / 03 / 2022, data from FlightAware [15]

Aircraft Type Number of Departures

A320 43

other Airbus 28

737-800 92

737-8200 1

other Boeing 15

EMB190 10

other 36

Total 225

On 09 / 03 / 2022 the majority of flights (109) departed south from runway 16 / 35 . 82 departures took place in westerly operation from runway 10R / 28L , while 34 flights departed easterly from the same runway.

4. UPDATING AIRCRAFT DEPARTING DUBLIN AIRPORT

As mentioned aircraft noise can be reduced by including newer aircraft in the fleet. We investigate a scenario where Ryanair replace all Boeing 737-800 operating from Dublin airport with its newest

Figure 3: L Amax noise reduction (di ff erence map) for departure of Boeing 737-800 subtracting 737- 8200 noise footprint

addition to its fleet, the 737-8200. This would reduce the noise footprint during departure by up to 12 dB(A). The L Amax = 55 dB(A) footprint of the Boeing 737-8200 is 50 % smaller than the footprint of the Boeing 737-800. Areas perpendicular to the take-o ff route benefit most from updating the aircraft, as shown in Figure 3. Figure 3 shows the di ff erence in noise contours between both aircraft for a simple take o ff trajectory. The previous modeling of the realistic airport operations is now updated to replace the Boeing 737-800 with the 737-8200 aircraft and the di ff erence in noise contours reported in Figure 4. If the Boeing 737-800 in Ryanair’s fleet would be replaced by 737-8200 aircraft, noise emission at Dublin Airport would decrease. This could benefit the surrounding areas, by reducing noise up to 5 dB during daytime (Figure 4). Dublin Airport reduces night time flights to a minimum. This already limits night time noise emissions. However, updating Ryanair’s fleet will also improve the night time noise footprint. In this case study, 11 out of 15 aircraft departing Dublin Airport on 09 / 03 / 2022 were Ryanair aircraft. The Boeing 737-8200 could reduce the night time footprint by up to 8 dB(A). The area in which noise exceeds the 55 dB(A) threshold during day time can be reduced by over 25 % with the new Boeing 737-8200 aircraft. An estimation of the number of residents a ff ected by the change in the departure noise footprint was made with the population data from the All-Island Census Atlas [16]. Based on the original model there were 22,600 residents within the 55 dB(A) contour line. With the updated model this reduced to 12,580, demonstrating a beneficial change in the noise exposure for in excess of 10,000 residents.

Noise Reduction Lmax in dB(A) 0< 2< 4< 6< 8< Scale 1:35166 10< ) 0.5 1 12<

Figure 4: Noise reduction (di ff erence map) at Dublin Airport after replacing Ryanair Boeing 737-800 aircraft with 737-8200, departure noise map, day and evening time (07:00-23:00), no evening time noise penalty applied

5. CONCLUSION AND OUTLOOK

Departures from Dublin Airport on 09 / 03 / 2022 were modeled for a 24 h window. 210 flights departed during the day-evening time (07:00-23:00), while 15 departures took place during night time (23:00- 07:00). The majority of departures from Dublin Airport were westerly and southerly departures. Ryanair departures made up almost 40 % of all departures from Dublin Airport that day. On this day Ryanair operated mainly Boeing 737-800 aircraft at Dublin Airport with the exception of one 737- 8200 aircraft. In future the percentage of 737-8200 aircraft operated on a given day will increase. In SoundPLAN the Ryanair Boeing 737-800 was replaced by its newest addition to the fleet, the 737- 8200. The 737-8200 has a 60 % smaller L Amax = 85 dB(A) noise contour footprint then the Boeing 737-800. This reduced the area in which noise exceeds the 55 dB(A) day time threshold by over 25 %. In addition over 10,000 residents in the > 55 dB(A) area around Dublin Airport are positively a ff ected by this change. It would reduce their day and evening time noise exposure to under 55 dB(A). This is a significant improvement to the environmental noise footprint of Dublin Airport despite a change to only 40 % of the aircraft operating in a given day. This overall departure noise reduction at Dublin Airport shows, that a change to an entire fleet can make a significant di ff erence. Ryanair’s decision to update their fleet will not only reduce their noise charges at airports but also benefit residents in airport surrounding areas. In addition, the new aircraft has lower fuel consumption and thus also fewer carbon emissions. This modeling work is a beginning to a comprehensive evaluation of the fleet level noise emission by Ryanair. Future investigations will evaluate next generation concept aircraft and demonstrate future

potential for noise reduction by the airline. This will form one pillar for a comprehensive approach to sustainability taken by the airline. In the further process of modeling arrivals and departures at Dublin Airport a scenario with additional noise-reducing technology on aircraft of other airlines could be employed. This would show how much noise around Dublin Airport could be reduced and what impact it has on residential areas. In addition, the influence of Ryanair’s changes at Dublin Airport can be evaluated. Arrival noise footprints will be added to the noise map and the impact on the airport surrounding residential areas assessed.

6. ACKNOWLEDGMENTS

This work is funded by the Ryanair Sustainable Aviation Research Center, a philanthropic activity at Trinity College Dublin.

REFERENCES

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