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A-1 Appendix A: Reagan Washington National Airport (DCA) Taxi Noise Measurements A.1 . DCA Tax i Noise Measurement Setup Aircraft taxiway noise was measured at Ronald Reagan National Airport (DCA) on June 30, and July 3, 2008. Sound level meters and a video system were deployed in order to obtain noise levels, aircraft speed, and positional information. Accessible measurement locations were selected in conjunction with airport operations personnel based on the prevailing weather conditions and active runway configuration. Both measurement locations are shown as red diamonds on the airport diagram of DCA in Figure A-1. Measurements conducted on June 30 and July 3, 2008 were at locations M1and M2, respectively. Measurements on June 30 only recorded aircraft pass-by after arrival on Runway 19 while taxiing to the terminal. Measurements on July 3 recorded idle noise of single and multiple aircraft at the holding pad prior to departure on Runway 19. Figure A-1. Washington / Ronald Reagan Washington National (DCA) Airport The June 30 measurement location was adjacent to the two primary taxiways J and K adjacent to runway 19 (Figure A-1). The measurement site was situated approximately 72 feet (22 meters) from the point of closest approach to an operation using Taxiway K and approximately 256 feet (78 meters) from the point of closest approach to Taxiway J (Figure A-2). The taxiway centerlines can be seen in Figure A-3 highlighted in bold yellow. Two Larson Davis 831 sound level meters (SLM) were placed
A-2 at positions Kilo-Fox 1 and Kilo-Fox 2 shown in Figures A-3. The SLM at Kilo-Fox 1 was placed 1.3 m (4.5 ft) above the ground and SLM at Kilo-Foxtrot 2 was placed to 1.4 m (4.8 ft) above the ground. The SLMs were programmed to collect A, C, and Un-weighted levels and 1/3 octave 1-second time histories. A photograph showing the equipment orientation to the taxiway is given in Figure A-4. Figure A-2. Measurement setup at DCA on 30 June 2007 Figure A-3. Close Up Schematic of Taxiway Pass-by Measurement at DCA on 30 June 2008 Figure A-4. Camera View of Taxiway Pass-by at DCA on 30 June 2008
A-3 Meteorological data was obtained from the DCA weather hourly report for the duration of the measurements. The weather data is shown in Table A-1. Table A-1. Meteorological Conditions 30 June 2008 Temperature 82 ºF Relative humidity 51 percent Atmospheric pressure 1009.7 mbars 3 July 2008 Temperature 87 ºF Relative humidity 40 percent Atmospheric pressure 1016.4 mbars Vertical marker posts were placed on either side of the SLM at distance of 6.5 feet. A video camera was placed 40 feet behind the SLM such that the distance to both vertical markers was equidistant. Rangefinders were used to verify distance from SLM to engine. Speed was estimated by elapsed time for aircraft to pass from right vertical marker to left marker. Traverse distance was determined by focal angle and geometry of camera, marker locations, and distance to engine. By this method the aircraft was assumed to be traveling at constant speed. Observations support the constant speed assumption. Figure A-5. Schematic of Taxiway Idle Measurement at DCA on 3 July 2008 Figure A-6. Camera View of Taxiway Idle at DCA on 3 July 2008 Measurements were made on 3 July 2008 to measure taxiway and holding block idle and acceleration noise. Larson Davis 831 sound level meters, vertical markers and video camera system were set-up in similar configuration to the earlier measurements. It was observed that aircraft would line-up along
A-4 centerlines arbitrarily named 1, 2 and 3 at holding block J at the beginning of runway 19, as shown in Figure A-5. The aircraft would queue-up in the holding block and hold at positions A, B, and C along the centerlines. During the measurements 1 to 5 aircraft were observed in the holding block at any given time. There were a few brief periods where no aircraft were in the holding block, which provided an ambient noise level measurement. A.2 . DCA Tax i Noise F ie ld Measurements On June 30 and July 3, 2008, Wyle measured the taxiway noise of 47 and 35 aircraft operations, respectively, ranging from regional jets to 737-700s. Figures A-7 and A-8 contain the field note log sheets from the June 30 measurements, while Figure A-9 through A-11 contain the field note log sheets from the July 3 measurements. Figure A-7. Field note log sheet for 30 June 2008 (part 1/2)
A-5 Figure A-8. Field note log sheet for 30 June 2008 (part 2/2)
A-6 Figure A-9. Field note log sheet for 3 July 2008 (part 1/3)
A-7 Figure A-10. Field note log sheet for 3 July 2008 (part 2/3)
A-8 Figure A-11. Field note log sheet for 3 July 2008 (part 3/3)
A-9 A.3 . DCA Measurement Analys is A total of 47 taxiway pass-by events were measured on 30 June 2008. From that dataset 20 were found to be free of extraneous noise such as arriving or departing operations. All events were arrivals taxiing from the runway to the terminal. The 20 events are listed in Table A-2. Table A-2. Measured Taxiway Pass-by Events at DCA on 30 June 2008 Event Number Tail Number Aircraft Type Engine Max Rated Thrust (lb) SEL (dB) 1 N675BR CRJ CF34-3B1 9220 98.3 2 N943AN B737-800 CFM56 26300 104.0 3 N279SK E145 AE 3007A1P 7580 87.5 4 N410AW CRJ 200 CF34 9220 99.2 5 N518AU CRJ CF34 9220 87.9 6 N342UA B737-300 CFM56 19500 106.8 7 N909DE MD88 JT8D 21700 103.8 8 C-FEJA CRJ 200 CF34 9220 99.0 9 N582CA CRJ CF34-8C5 14500 96.2 10 N994DL MD88 JT8D 21700 91.5 11 N750UW A319 CFM56 22700 91.0 12 N908ME B717-200 BR 700 17000 100.1 13 N871BE CRJ 200 CF34 9220 98.4 14 N359NB A319 CFM56 22700 104.2 15 N16703 B737-700 CFM56 22700 102.4 16 N735TS E135 AE 3007A 7580 102.0 17 N458AW CRJ 200 CF34 9220 91.9 18 N916DE MD88 JT8D 21700 105.1 19 N379UA B737-300 CFM56 19500 97.6 20 N430AW CRJ 200 CF34 9220 90.0 A method was devised to obtain free-field spectral directivity data for each of these events at a reference distance of 150 ft. Using video images and scaling, the ground track of each event was estimated at times corresponding to the third-octave band time histories. An omni-directional source was run in a Wyle aircraft noise simulation model to calculate the effects of spherical spreading, absorption, and the ground for each instance in the ground track. This ray-tracing analysis used the same atmospheric conditions as during measurements, allowing these elements to be removed from the noise measurement data. The next step in the analysis was to apply spherical divergence and atmospheric attenuation based on standard atmospheric conditions to the data in order to obtain reference directivity data at the desired radius. In Figures A-12 through A-14 the corrected longitudinal directivity is plotted by aircraft types; B737 and A319s, MD88s, and CRJs, respectively. In Figure A-12 the A319 event is included with the B737 events because they both have the same CFM56 series engine. The overall sound pressure level (OASL) is plotted versus directivity angle. Events at the 72 feet distance span a wider range of directivity angles than the 256 feet distance. The angle increases rapidly when the aircraft is near to the SLM (90º) and changes slowly when the aircraft is at the extent angles.
A-10 737 & A319 Taxiway Longitudinal Directivity 70 75 80 85 90 95 100 20 40 60 80 100 120 140 160 Directivity Angle (deg) O A SL (d B ) B737 13kts Evt2 B737 12kts Evt6 B737 14kts Evt15 B737 8kts Evt19 A319 17kts Evt14 Figure A-12. Longitudinal Directivity of B737 and A319 Events MD88 Taxiway Longitudinal Directivity 70 75 80 85 90 95 100 20 40 60 80 100 120 140 160 Directivity Angle (deg) O A SL (d B ) MD88 8kts Evt7 MD88 12kts Evt10 MD88 23kts Evt18 Figure A-13. Longitudinal Directivity of MD88 Events
A-11 CRJ Taxiway Longitudinal Directivity 70 75 80 85 90 95 100 20 40 60 80 100 120 140 160 Directivity Angle (deg) O A SL (d B ) CRJ 16kts Evt1 CRJ 10kts Evt3 CRJ 12kts Evt5 CRJ 15kts Evt8 CRJ 14kts Evt13 Figure A-14. Longitudinal Directivity of C/RJ Events One of the primary considerations of taxi way noise modeling is that of the aircraft spectra, and in particular the change in spectra with directivity angle. Given the geometric orientations of taxiways to community receptors, it is possible for certain regions to be repeatedly exposed to taxi operations at a narrow range of directivity angles relative to the source. Aircraft measurements at the limits of the front and back directivity angle, the aircraft is at a considerably greater distance than point of nearest approach. When accounting for propagation (spherical spreading, absorption and ground effect) one can see that as an aircraft is approaching there is considerably more high frequency content. This is likely due the turbine whine and blade passage frequency emanating from the front of the engine. As the aircraft passes-by and moves away there is more low frequency content. This is likely due to the thunder and turbulent wake emitted from the aft of the engine. B737 and A319 Taxiway Longitudinal Directivity 60 65 70 75 80 85 90 95 100 20 40 60 80 100 120 140 160 Directivity Angle (deg) O A SL (d B ) B737 13kts Evt2 B737 12kts Evt6 B737 14kts Evt15 B737 8kts Evt19 A319 18kts Evt11 A319 17kts Evt14 HMMH B737-300 Fit Figure A-15. Comparison of B737 and A319 Events
A-12 A curve fit was determined as representative of measured B737 taxiway longitudinal directivity, shown as an orange curve in Figure A-15. This representative 737 directivity profile is used for the detailed single event simulation studies presented in the main report in Chapter 4. A total of 35 taxiway idle events were measured on 3 July 2008. From that dataset 16 were found to be free of extraneous noise such as arriving or departing operations. Several different combinations and aircraft configurations were measured. The 16 events are listed in Table A-3. Table A-3. Measured Taxiway Idle and Acceleration Events at DCA on 3 July 2008 Event # AC in Hold Description: Lane # & AC Type Start Stop SEL Leq 1 2 3A - A319, 3B - E145 11:14:00 11:15:55 103.1 83.8 2 3 1A - CRJ200, 3A - A319, 3B - B737-800 11:22:15 11:22:50 98.4 83.1 3 3 3A - A319, 3B - B737-300, 3C - A319 11:30:35 11:31:25 100.6 83.1 4 2 2A - A319-112, 3A - A319-112 11:32:55 11:33:25 100.9 85.4 5 3 3A - A319, 3B - MD88, 3C â unkwn narrow body 11:39:15 11:40:00 100.3 83.4 6 4 1A - CRJ200, 1B - A319, 3A - MD88, 3B - NB 11:43:10 11:44:30 102.0 82.9 7 3 1A - A319, 3A - MD88, 3B - NB 11:45:55 11:46:15 95.2 81.6 8 1 3A - E135 11:54:03 11:55:40 96.3 76.5 9 0 No Aircraft 11:56:15 11:56:55 86.3 70.3 10 0 No Aircraft 11:58:05 11:58:40 80.8 65.4 11 1 1 in #3 - 737 11:59:34 11:59:55 100.5 87.5 12 2 1A - B737-300 rolls to 19 for Dep., 3A - B737-300 11:59:55 12:00:15 98.3 85.1 13 0 No Aircraft 12:06:25 12:07:15 89.8 72.8 14 0 No Aircraft 12:08:00 12:09:00 84.0 66.3 15 1 1A - B757 12:09:25 12:09:44 91.4 78.6 16 2 3A - A319, 3B - E190 12:10:50 12:11:30 97.3 81.3 Unfortunately due to the amount of traffic during this measurement period, we were unable to obtain data from a single aircraft accelerating from a stop. There were only three brief times when only one aircraft was in the holding block. This measurement dataset will be useful for validation of a future taxiway model, however at present due to a commingling of noise events with various aircraft in the holding block at the same time, the data could not be used directly to extract a single noise event. A few notable events are listed in Table A-4. Table A-4: Notable Events during DCA taxi noise measurement period Event # Description 3 Three similar aircraft lined-up 4 Two of same aircraft side-by-side 8 One aircraft 11 One aircraft 16 Two similar aircraft lined up