Enhanced Modeling of Aircraft Taxiway Noise, Volume 1: Scoping (2009) / Chapter Skim
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Pages 45-72
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From page 46... ...
46 45 45 50 50 50 50 55 50 55 60 65 60 70 75 8080 90 95 100 100 40 40 40 40 45 45 45 50 55 50 60 55 65 65 70 75 70 75 8585 100 40 40 40 40 45 45 45 55 50 50 55 55 65 60 70 75 75 8585 95 40 40 40 4045 45 45 45 50 55 50 60 60 60 60 65 65 70 75 80 859095 100 40 40 40 45 45 45 45 50 50 50 55 55 60 60 65 65 70 75 80 90 40 40 45 45 45 50 50 50 55 55 60 60 65 70 75 0 90 X-Ft Y -F t -5000 0 5000 -4000 -2000 0 2000 4000 SEL-A 100 95 90 85 80 75 70 65 60 55 50 45 40 35 B737-700 Taxi Operation Heading East Full Directivity T=480 (2%)
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47 0.5 1 1 1.5 1.5 1.5 1.5 2 2 2 2.5 2.5 2.5 3 X-Ft Y -F t -10000 -5000 0 5000 10000 -10000 -5000 0 5000 10000 SEL-A 3 2.5 2 1.5 1 0.5 B737-700 Taxi Operation Heading East Full Directivity Spheres Difference Plot T=4800 (20%)
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48 One can see from the SEL contour plot (Figure 41) and the difference (Figure 42)
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50 4.2. Multiple Operations In the ideal scenario, detailed ground operations will be modeled as individual tracks where the position and state of the aircraft is known as a function of time.
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51 • Step 1. Create an over-flight track consisting of the necessary number of segments to model straight segments, runway crossing points, and turns.
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52 Figure 43. Complex taxi configuration with high-fidelity taxi movements.
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53 As shown in Section 4.3.4, run up operation data is consistent with departure NPDs in INM, therefore only departure NPDs will be utilized in this analysis. It is the differential in the DNL contours that is of importance, not the absolute value of the contour level.
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54 Within this analysis any time an aircraft holds at a fixed position and exceeds a specified duration threshold, it can be modeled as a run up operation within INM as a static operation with the appropriate duration, location and heading. A comparison of a holding duration threshold of 1 and 5 minutes were considered (Figure 45)
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55 4.2.2.1. Moving vs.
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56 Lumped Time in Mode Analysis: All operations at one location. At one extreme, each run up could be modeled at the individual locations of the aircraft with the appropriate orientation.
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57 determine a broadly applicable modeling philosophy for selection of the three run up centroids. However, it was felt that at each location operations would be represented best by pointing the aircraft the 4 cardinal directions (East, West, North, South)
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58 Figure 49. All taxi tracks and 6 nominal tracks.
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59 Potential improvements to this modeling scenario would be to model the direction along the taxi ways tangent to the taxi heading, but modeling the run ups in the center of the taxi turning locations with all possible heading directions. This leads to the obvious parallels with detailed flight track analyses, namely the creation of backbone tracks based on statistical analysis, the assignment of operations to individual taxi segments (over flights in INM)
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From page 60... ...
60 exposure is directly proportional to the run up duration time. In terms of sound exposure level, this may be represented by Equation 1.
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61 and hence the extrapolation procedure, and also the difference in spectral classes and hence absorption rates for the two different sets of NPD curves. Figure 51.
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62 are used to define static operations. An important exception is made here: in order to more closely compare run up versus over flight operations, the over flight will be modeled with the previously developed user defined SEL NPD extrapolated departure thrust settings in order to more closely match the Run up conditions.
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64 levels. If such a simple change in INM would bring predictions and measurements in alignment, it would be the simplest and least expensive way to model taxi noise in INM.
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65 737-700 Taxi Thrust Sensitivity & comparison with Measurements 10 20 30 40 50 60 70 80 90 100 100 1000 10000 100000 Distance (ft)
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66 4.3.5. Specifying NPD Curves Section 4.3.6 demonstrated that INM NPD data extrapolation to taxi / idle thrust settings did not agree particularly well with measurement data.
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67 737-700 NPD SEL Curves 40.0 50.0 60.0 70.0 80.0 90.0 100.0 100 1000 10000 100000 Distance (ft)
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68 Figure 58. Contour comparison taxi operation: INM7, user defined, user defined + modified 4.3.6.
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69 modeled here. This example demonstrates INM's use of finite track segments and SEL NPD curves for predicting noise contours from moving operations.
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70 Figure 60. INM single segment moving taxi operation at 0 ft AGL.
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71 Where ASref is 160 knots and ASseq is the speed of the aircraft on a track segment. An increase in speed will decrease the SEL.
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From page 72... ...
72 seconds. The solid blue contour lines result from modeling two operations in INM.
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