Noise-related challenges in combined commercial and military opera- tions at an airport Jan Anders Marheim 1 Avinor AS P.O.Box 150 N-2061 Gardermoen, Norway Michael James Newman 2 Avinor AS P.O.Box 150 N-2061 Gardermoen, Norway

ABSTRACT At Harstad/Narvik Airport Evenes, a NATO QRA detachment using F-35 fighter planes has changed the noise characteristics at the airport dramatically. The challenges of determining the correct health hazard values to avoid hearing damage to passengers and employees at an oper- ational airport is difficult. Initial noise mapping shows large areas around the terminal building and the car park shows very high noise levels during F-35 take-offs using afterburner. The noise level increases rapidly during a take-off, but it is not comparable to an impact noise event.

The focus of the work is twofold; Finding the right noise limits to avoid hearing damage risk at the same time as establishing noise abatement measures that are necessary to avoid hearing impairment to employees and passengers on their way to and from aircraft. A noise limit of LASmax = 115 dB is established but insufficient due to the spectral and temporal quality of the noise from the F-35.

1. INTRODUCTION

This paper describes the aircraft noise situation at Harstad/Narvik airport Evenes in Norway. The airport is owned and operated by the Norwegian company Avinor. Through a government decision dating back to 2012, the Norwegian Air Force has been requested to establish a Quick Reaction Alert (QRA) base at Evenes. QRA is a state of readiness of the air defense maintained at all hours of the day by NATO air forces. A QRA response that involves fighter aircraft being scrambled to investigate an infringement of any NATO country’s airspace. The QRA requires a fighter plane to be airborne in 15 minutes or less. A QRA departure most often involves using the engine’s afterburner, increasing the thrust and thereby the acceleration of the aircraft. The base at Evenes is equipped with F-35 Light- ning II for this mission.

1 Jan.anders.marheim@avinor.no

2 Michael.James.Newman@avinor.no

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The F-35 is said to have a much louder noise signature than its predecessor the F-16 Fighting Falcon. Hence, the need for an investigation into the noise levels and contours around the airport was of the utmost interest to the public as well as to Avinor.

2. NOISE MAP CALCULATIONS

Based on the decision to establish a QRA base at Evenes, a noise impact assessment was per- formed. There will be an estimated 104 QRA-scrambles using F-35 annually. In addition, there will be several departures for practice purposes and from other visiting aircraft. The total number of de- partures is estimated at close to 800 annually. This is in addition to the annual number of 7500 com- mercial flights. Additionally, there are just over 1100 medical emergency flights annually. The noise mapping showed that the noise contours of the areas surrounding the airport is dependent solely on the QRA activities.

Figure 1: Noise zones with and without military operations. Red contour is at LDEN 62 dB and yellow is at LDEN 52 dB

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2.1. Detailed noise calculations

A detailed noise calculation performed using the Norwegian software NORTIM, using a QRA departure as the noise source shows very high maximum noise levels on the terminal building facades and in the areas where the car park is located and at the places for boarding/deboarding the aircrafts. Areas with maximum noise levels exceeding 115 dBA are considered to be a health hazard to people being in these areas. Figure 1 shows the results of the noise calculations. Due to a rather coarse grid, 78 meters between grid points, the interpolation shows some anomalies. The areas marked in red stripes will also be considered being part of the health hazard areas.

The software is not capable of calculating MaxPeak values, hence the contours are based on the LASmax-levels.

Figure 2: Calculated LASmax noise contours from a QRA departure.

3. NOISE MEASUREMENTS

In order to verify the calculation results, and to determine the MaxPeak levels, a measurement campaign was planned and performed. The results of this campaign show very good agreement be- tween the measured and calculated noise levels. However, the measurements also showed an alarming level of MaxPeak, even outside the LASmax contours of 115 dB.

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Measure-

Take-off direction

Number of F-35

AB/Mil Pwr LASmax

MaxPeak Occupational health limit = 130 Main gate 17 2 AB 119,9 – 120,6 136,3 – 138,5 17 14 Mil Pwr 114,4 – 118,9 132,0 – 136,3 35 6 AB 116,4 – 119,9 137,4 – 138,6 35 8 Mil Pwr 113,8 – 115,5 132,1 - 133,1 Gate 30 17 0 AB - - 17 14 Mil Pwr 107,3 – 111,6 125,5 - 132,6 35 6 AB 105,0 – 109,1 121,9 – 127,4 35 8 Mil Pwr 90,1 – 109,0 110,4 – 129,7 Table 1: Noise measurements during F-35 take-off

ment location

Hearing damage hazard = 115

The measurement results show that there are generally higher levels when using afterburner as opposed to the military power setting. The military power setting is in an interval, making it difficult to determine more precisely what the noise levels are. The levels also depend on other variables, including take off profile, weight of the aircraft and whether conditions. Figure 3 below shows the changes in noise level and frequency content. Every QRA-departure con- sist of at least 2 F-35 separated by a few seconds. It is clear that the noise levels are rising quickly, and there is a lot of energy at low frequencies. The fast rise in noise level makes it challenging for the middle ear to adjust and protect.

Figure 3: Noise levels during a F-35 departure using afterburner, pre-A-weighted spectrum

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The low frequency content makes for carefully choosing the correct sound insulation materials and solutions.

4 ESTABLISHING THE CORRECT NOISE LIMITS

Based on the impact assessment 1 , the zoning plan listed a limiting value for the maximum noise level LASmax as the only parameter for the areas close to the terminal building. This is referenced to a report published in 2001 on low flying military aircrafts and their expected noise levels 2 . It is stated that “given that the low flying occurs occasionally and that nobody is frequently exposed to maximum noise levels above 115 dBA, the probability of a hearing loss is minimal”.

Independent of this requirement, the occupational health regulation states that a maximum Peak value MaxPeak of 130 dB(C) is not to be exceeded at any time. This is valid for everybody working at the airport, including personnel on board the aircrafts. This raises the question of why the Max- Peak values is not included in the zoning plan.

The question was raised in an enquiry to the Norwegian Institute of Public Health (FHI). FHI produced a report concluding that the limiting value of LASmax is sufficient and takes into account the total noise situation.

A main concern is if it is correct that the noise limit for occupational health is not valid for pas- sengers in the same noisy environment. It could be argued that the Peak-values are based on very rapid changes in the noise levels, e.g., a gun shot or hammer blow, while the change in noise level for a QRA departure is somewhat slower. The Acoustic reflex, often known as the Stapedius reflex or muscle, is a contraction of the middle ear muscle in response to moderate to high level noise. The contraction alters the impedance of the middle ear system and hence protects against loud noise. A study by Gregory A. Flamme et al published in the International Journal of Audiology 3 found that about 25 % of all adults are missing these reflexes. Since the acoustic reflexes are not sufficiently prevalent, it is not suited for health hazard assessment the study found.

There is no doubt that the noise levels that occur during a QRA departure is loud and frightening to people less experienced with airports and aircraft noise. 5. MEASURES TO PROTECT PASSENGERS AND OTHERS AT THE AIRPORT

Having established a relationship between the measured and calculated noise levels, there are four main areas of concern. These are

 Passengers walking from the car park to the terminal building  Passengers and crew boarding/deboarding aircraft  Employees working in the noise zone  Medical transport transfer

The transfer of passengers from the car park to the terminal building could be solved by build- ing a covered parking garage with a covered passenger bridge into the terminal building. The park- ing garage needs to be a closed structure in order for the noise levels not to enter the building. The building materials needs to be chosen carefully to ensure the proper noise insulation. The covered walkway to the terminal building will also have to be noise insulated the same way.

The transfer of both passengers and crew between the terminal building and aircraft could be solved by building jetways with flexible connections up against the aircraft itself. This will give ap- proximately 10 dB reduction in the outside noise level which is sufficient noise insulation in order

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to avoid hearing damage. For the national flights, Boeing 737 or similar are used. There are a num- ber of solutions that meet the requirements on sufficient sound reduction. For regional flights, De Havilland Dash 8 is most commonly used. There are no known solutions for boarding/deboarding of these aircraft that gives any sort of noise protection for the passengers.

Employees working in the areas will have to wear proper hearing protection. It is also important that the protection must be worn at all times since the noise levels often occurs abruptly, and in some instances without warning.

Medical transport transfer is by far the most challenging. The airport is a hub for transferring patients from an ambulance to an aircraft for further transport and vice versa. In this situation, there are a number of people involved in the transfer, where the patient is often on a gurney. This takes place outdoors, on a site close to the runway. The only viable option seems to be to move the trans- fer site out of the areas with the hazardous noise levels. This will require allocating new areas, new traffic patterns around the airport apron and possibly also changed security issues.

Figure 4: Medical transfer during a F-35 departure Courtesy: Hilde Høiem-Storås, Luftfartstilsynet

6. IMPLEMENTED TEMPORARY MEASURES

The QRA activities have already begun, and there is an urgent need for measures that warns the public about the health hazard in the area. A couple of items are in place, but these are temporary,

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while permanent measures are being planned and implemented. Figure 5 shows a sign along the road leading into the airport car park. Figure 6 shows the LED-signs on the terminal building wall warning arriving passengers and employees of a noise event in progress.

Figure 5: Warning sign on the road leading to the airport

Figure 6: Warning sign on the terminal building announcing a noise event in progress

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7. CONCLUSIONS

From a noise perspective, mixing commercial and military activities at an airport has proven to be challenging. This is especially true when the military activities include sudden, very loud noise events. The noise levels obtained at a departure with a F-35 is very loud and is a cause for concern for passengers and employees alike. The calculated and measured noise levels show values well above limits for risk of hearing damage in areas open to the public. Proper precautions need to be taken, and there is a need for physical measures.

The established noise limit appears to be insufficient due to the spectral and temporal quality of the noise from the F-35. A wider approach to the noise source indicates that there is a need for more noise descriptors. Employing the noise limit for MaxPeak used in occupational health in combination with the LASmax seems to cover the situation at hand.

Several different areas are affected by the noise from a QRA departure, and there are different requirements that need to be met. Passengers, employees and medical transport are all groups and areas that need special attention. Protecting the passengers going from the car park through the ter- minal building means adding sound insulated structures on both ends. A parking garage will give good noise insulation, while a jetway will reduce the outside noise level sufficiently to avoid hearing damages.

The employees working in the areas will need to have proper hearing protection. Simultaneously, there is a need for information on how to use the protective gear properly.

Medical transport transfer is the most critical item. The only viable option seems to be to move the transfer site out of the areas with the hazardous noise levels.

8. ACKNOWLEDGEMENTS

The authors wish to thank Avinor for facilitate the measurements and pursue the best knowledge available in order to decide the correct noise limits based on facts. 9. REFERENCES

1. AIM. Evenes flystasjon og Harstad/Evenes lufthavn, Evenes. Forslag reguleringsplan med kon-

sekvensutredning. ALM-95-00-R-RAP-001, rev 02 (2018). 2. NOU 2001:15 Forsvarets områder for lavtflyging. Utredning fra et utvalg oppnevnt av Forsvars-

departementet den 24. september 1998. Avgitt 18. oktober 2000. 3. Gregory A. Flamme, Kristy K. Deiters, Stephen M. Tasko & William A. Ahroon Acoustic re-

flexes are common but not pervasive: evidence from the National Health and Nutrition Examina- tion Survey, 1999–2012 International Journal of Audiology 2017; 56: S52–S62.

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