| Topic: | Re:Re:Re:3rd runway noise in Chiswick | |
| Posted by: | Tom Pike | |
| Date/Time: | 02/02/08 18:34:00 |
| Jeff, You can use the noise contour maps to extract a plot of the dB's right along the existing and proposed flightpaths. In 2002 the north runway arrival path is at 60 dBA Leq where it meets the Thames leaving Grove Park. It will drop by less than 1 dB in 2015 with mixed mode, but will be down to 57 dB once the third runway comes in. From the same map the noise under the flightpath to the third runway itself will be at 56 dB at Turnham Green in 2020. The problems with your calculation is first that mixed mode won't double the flights, just increase them by 17% from 2002. That's because you can't just fit a departure between two arriving flights without increasing the spacing. That 17% increase will push up the noise by less than a dB, which is more than compensated by the retirement of the noisiest planes in the next few years. And you don't need to speculate on the aircraft mix for the third runway in 2020 - according to the consultation it will be almost all A320 series or equivalent. They are 6 dB quieter on approach than the 747-400s. The Caravelles are already gone and the MD-11's will have long been retired by then. I think the proposed contour plots showing the third-runway flightpaths about 4 dB quieter than Grove Park currently are quite reasonable. |