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3.5.1
Departures (Figure 2-2)
Departure routes have been identified for runway F 1 when departing in the 075°T direction. All of these routes may usefully be used by the studied aircraft experiencing engine failure at the critical point followed by a circumnavigational route to return to the airport. The routes are more fully described at Appendix B.
are
Departures from the southerly runway D in the 050°T direction similar to those for runway F 1 and are also described at Appendix
B.
A degree of flexibility exists in designing south-westerly departure routes. There will be no
no difficulty in designing engine failure routes in this general direction except for the distance required to be flown for a return to the airport.
3.5.2 Approaches (Figure 2-3)
The objective of the study of possible approaches and missed approaches to the runways is to establish whether ILS Category I or Category II OCHs of 200 feet and 100 feet, respectively, are achievable. In broad terms, Category II (the most demanding) can be achieved for each runway of the scheme. Details are at Appendix B.
3.5.3
Noise Exposure Forecasts
In order to assess the degree to which noise generated by the Scheme "A" airport configuration will be compatible with existing and proposed land uses in the Deep Bay area, estimates of the Noise Exposure Forecast (NEF) expected from operations in the study year 1995 were derived. The NEF is an index of noise exposure which takes into account the different degrees of noisiness resulting from different aircraft types, their different altitudes and rates of climb, the number of average flyovers per day, and the time of day they are flown (night flights make a greater contribution to NEF than daytime ones). The index is designed so that an NEF of 0 dB
an NEF of 0 dB can be considered to be completely acceptable and 50dB completely unacceptable for areas of human use. An NEF of 25dB (referred to herein as NEF 25) has been selected in previous Hong Kong replacement airport studies as a level above which new residential development is not recommended. Exposure to single events is treated at Appendix D.
of
To derive these estimates within the limited time constraints of this study, both manual and computer analysis techniques were used, as described in Appendix D.
First, a computer program called the Integrated Noise Model (INM) developed by the U.S. Federal Aviation Administration, was used to derive estimates noise levels for selected simple straight-in and straight-out arrival and departure scenarios. Then these values were modified manually to reflect the runway configurations and individual options of the cases being considered. In fine detail, this method is likely to produce contours which differ slightly from contours generated entirely by computer, however the principles employed are virtually the same.
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