400 ft over center mic 80 kt 7 8 d 6 deg decelerating

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(400 ft over center mic) 80 kt 7, 8 D 6 deg decelerating ( “) 66 kt 9, 10 E 9 deg decelerating ( “) 54 kt 11, 12 F Quiet critter (“) - multisegment, decel 63 kt 13, 14, 15 G HAI Medium ( “) - multisegment, decel 50 kt 16, 17, 18, 19 H HAI Light ( “) - multisegment, decel 54 kt 20, 21, 22 Differential corrections Multi-segment noise-abatement approach profile Standard constant glideslope approach Ground ref. GPS RASCAL Figure 1. Schematical diagram showing LDGPS-guided rotorcraft noise-abatement approaches in a confined urban area.
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13 1400 1200 1000 800 600 400 200 Flightpath angle (deg × 100) Path height (ft) Rate of descent (fpm) Airspeed (kt × 10) 1400 1600 1200 1000 800 600 400 200 1400 1200 1000 800 600 400 200 0 .5 1.0 1.5 2.0 2.5 3.0 .5 1.0 1.5 2.0 2.5 3.0 Distance from heliport (nm) HAI-M (a) HAI-L (b) Quiet (c) 0 0 .5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Figure 2. Approach profile details: (a) HAI-Medium, (b) HAI-Light, (c) Quiet.
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14 3000 2000 1000 -1000 -2000 -3000 0 Y Distance (feet) 3000 2000 1000 -1000 -2000 -3000 0 Y Distance (feet) 3000 2000 1000 -1000 -2000 -3000 0 Y Distance (feet) (a) 6 ° descent approach (b) 9 ° descent approach (c) 12 ° descent approach EPNL, EPNdB High Low Distance (feet) -4000 -3000 -2000 -1000 1000 2000 3000 4000 0 (a), (b), (c) Varying glideslope @ 80 kts Figure 3. EPNL ground footprints in descent flight.
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15 3000 2000 1000 -1000 -2000 -3000 0 Y Distance (feet) 3000 2000 1000 -1000 -2000 -3000 0 Y Distance (feet) 3000 2000 1000 -1000 -2000 -3000 0 Y Distance (feet) (d) 60 Knots; 9 ° glideslope (e) 80 Knots; 9 ° glideslope (f) 100 Knots; 9 ° glideslope EPNL, EPNdB High Low -4000 -3000 -2000 -1000 1000 2000 3000 4000 0 Distance (feet) (d), (e), (f) @ 9 deg glideslope with different constant speeds Figure 3. Concluded.
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16 10 9 9 5 8 8 7 6 4 5 1 2 3 1 10 6 7 300 600 900 1200 1500 1800 2100 2400 0 10 20 30 40 50 60 70 80 90 100 110 120 3 ° 6 ° 9 ° 12 ° 130 Airspeed (knots) Glideslope Noise scale: (least to most noisy) Quiet HAI-M HAI-L Rate of descent (fpm) Figure 4. Tested noise-abatement approach profiles in the plane of airspeed vs. rate of descent.
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17 300 600 900 1200 1500 1800 2100 2400 0 10 20 30 40 50 60 70 80 90 100 110 120 γ = 3 ° 6 ° 9 ° 12 ° 130 Airspeed (knots) Rate of descent (fpm) "Quiet" 102 104 106 dB 98 110 ψ = 177 ° ψ D r/D = 1.505 θ = 23 ° Mic No. 5 α TPP V 108 106 104 102 100 (a) Center mic (#5) Figure 5. BVI noise in descent – Langley 14- by 22-Foot Subsonic Wind Tunnel data.
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18 300 600 900 1200 1500 1800 2100 2400 0 10 20 30 40 50 60 70 80 90 100 110 120 γ = 3 ° 6 ° 9 ° 12 ° 130 Airspeed (knots) Rate of descent (fpm) "Quiet" 113 ψ = 133 ° ψ D θ = 25 ° Mic No. 12 α TPP V V 1.4D 102 105 110 110 111 107 dB (b) Starboard mic (#12) Figure 5. Concluded.
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19 300 600 900 1200 1500 1800 2100 2400 0 10 20 30 40 50 60 70 80 90 100 110 120 γ = 3 ° 6 ° 9 ° 12 ° 130 Airspeed (knots) Rate of descent (fpm) "Quiet" ψ = 180 ° ψ D θ = 25 ° α TPP V V r = 1.5D 104.6 105.5 103.2 103.7 103.3 100.9 100.6 99.6 99.4 99.7 99.4 99.4 100.1 99.9 100.5 100.9 102.1dB 101.6 101.2 100.5 100.0 102.1 101.1 (a) Center mic (#3) Figure 6. BVI noise in descent – DNW tunnel data.
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20 300 600 900 1200 1500 1800 2100 2400 0 10 20 30 40 50 60 70 80 90 100 110 120 γ = 3 ° 6 ° 9 ° 12 ° 130 Airspeed (knots) Rate of descent (fpm) "Quiet" ψ = 150 ° ψ D θ = 25 ° α TPP V V r = 1.5D 105.5 106.3 102.7 102.5 101.7 102.0 104.8 104.1 104.5 103.5 101.8 103.9 103.8 105.1 101.1 103.7 104.3dB 104.4 104.8 104.6 103.0 103.7 103.2 104.3 Mic No. 9 (b) Starboard mic (#9) Figure 6. Continued.
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21 300 600 900 1200 1500 1800 2100 2400 0 10 20 30 40 50 60 70 80 90 100 110 120 γ = 3 ° 6 ° 9 ° 12 ° 130 Airspeed (knots) Rate of descent (fpm) "Quiet" ψ = 210 ° ψ D θ = 25 ° α TPP V V r = 1.5D 95.7 97.1 97.5 97.1 95.2 95.1 97.1 97.8 95.0 95.2 94.5 95.5 95.3 95.4 95.2 96.3 96.7dB 95.9 95.6 93.5 91.8 96.0 93.8 96.3 Mic No. 6 (c) Port mic (#6) Figure 6. Concluded.
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22 * * * * * * 1000' 2000' 3000' 4000' 6000' 7000' 5000' 7000' 6000' 4000' 3000' 2000' 1000' 8000' 500' 1 4 2/3 (1.2 m) Microphone 1000 ft Laser eye safe range STOL aim point (Altitude 141') (Altitude 150') (Altitude 150') (Altitude 165') Runway 35: (Altitude 129') MTR radar DGPS ground station NASA complex TTR radar/laser Crows tower
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