TNAG-1174-FCO40-1476-Proposed-replacement-airport-for-Hong-Kong-at-Deep-Bay-or-Ch-1982 — Page 144

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these paths along the route. Since the paths converge on the 185 degree radial centered on Cheung Chau island, the paths are only expected to vary significantly between the end of the runway and the neighborhood of the Tai Lam Chung Reservoir. Since actual flight paths vary with wind conditions, loading, and pilot judgement, the occasional flight over Fairview Park may not be completely avoidable with this turn, even though the average track lies slightly to the west. However, it appears that such occasions could be minimized with appropriate traffic control instructions to pilots wishing to take this course.

In cases where all departures or all arrivals make a given turn, the procedure for estimating noise exposure levels along the track was simply to determine the width of the straight-in or straight-out contour at measured points along the track and apply these same widths to equal measured distances along the curved track. In the only case where flights diverged among two tracks, northesterly departures, the following steps were taken. First, the percent of aircraft on each track was estimated based on

expected preferences by flights according to destination (Table 9-2). Based on Reference 2, flights preferring an early turn to the south are those with westerly destinations from Bangkok to Djakarta (43.5 percent). Flights preferring straight-out departures are those destined northward to Chinese cities and Seoul (12.5 percent). Remaining flights are assumed to follow the turn over San Tin to Tolo Harbor and points east (44 percent).

The contribution to the total NEF by aircraft type i at a point near flight path j is given by:

where

NEFij

=

i j

i j

L ij + 10 log (Nd

+ 16.7 Nn )

-

88.0, dB (D-1 )

PNE

Lij

PNE

i j

Na

i j

Nn

16.7

and

88.0

is the average effective perceived noise level in dB, at the point for the given aircraft type and flight track,

is the number of flights by the aircraft along the track during daytime (0700 to 2200) hours,

is the number of flights by the aircraft along the track during nighttime (2200 to 0700) hours,

is a factor which effectively makes each nighttime operation equivalent to ten daytime operations (9 nighttime hours divided by 15 daytime hours, multiplied by 16.7 is 10.0),

-

is an arbitrary constant intended to make NEF correspond to a condition of no noise impact for even the most sensitive activities.

9-4

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