The results from the airport noise monitoring station that SFO installed in my very own yard for two weeks have come back. You can see the equipment and some of the background here. The monitoring was continuous around-the-clock, but I also kept track of 15 incidents that I found to be disturbing and gave them to the Airport Noise Abatement Office (ANAO). They kindly correlated these incidents with specific flights and their parameters.
Without getting into too much technical detail about A-weighted vs C-weighted (for low frequency sound) or the peak noise level of an event (Lmax) or the Sound Exposure Level that compresses the noise energy into one second, the measurements show:
The monitoring site at the Burlingame Park Neighborhood is relatively quiet with ambient noise levels of 48dBA, considering that most of the neighborhood is in an urban community setting. On an average day, there were 229 overflights, out of which 65 exceeded the noise monitor threshold and recorded a noise event. These events included departing aircraft engine start, ground idling, take-off thrust and initial climb thrust. Runways 01-Left and 01-Right departing aircraft accounted for the vast majority of the noise events recorded by the monitor.
The majority of SFO Aircraft noise events occurred between 12:00 am and 2:00 am, 5:00 am and 8:00 am and 5:00 pm through 11:59 pm. On average, there were 26 nighttime noise events during the duration of the monitoring session.
For this measurement the average aircraft generated Maximum Noise Level (LCmax) was 73dBC and the average Sound Exposure Level (LCE) was 83dBC.
The 15 events I flagged to the ANAO were mostly between 11 pm and 1:30 am since rousing myself to send myself a text to capture the exact time wasn't advisable around 3 am when some really bad events occur. Two examples of the correlation are:
11:02 pm: A Qantas Airways’ Boeing 747-400, Flight QFA074 to Sydney, Australia, started its takeoff roll on runway 28L at 11:01:35 pm. The LMax was 68.7 dB, the SEL was 76.2 dB and the event was 42 seconds long. (28L is one of the two the long runways that takes planes over Brisbane).
11:50 pm: An American Airlines’ Airbus A321, Flight AAL2902 to Charlotte started its takeoff roll on Runway 1R at 11:50 pm. The LMax was 65.1 dB, the SEL was 77.1 dB and the event was 40 seconds long. (Runway 1R is the southern short runway that is closest to Burlingame at its origin).
As part of our on-going legal action that has yielded a partial "win" as described here, one of the challenges we have is convincing a judge that "substantial changes" in airport operations have occurred. If that can be shown, then the idea that only people who have owned their homes since before 1980 can claim damages becomes invalid. So I read with some interest the SF Chronicle article from Sept. 13 about pilots transposing the runway numbers that they punch into their computers that then determine from the runway length how fast to get airborne. It's a fascinating and somewhat scary read, but the part that might shed some light on our run-up and back-blast concerns is
By registering runway 10L instead of 01L, the pilot made the computer system think it had 4,220 feet more runway than it actually had, investigators found. Runway 10L is 11,870 feet long; 01L is 7,650 feet. The computer alerted the captain to use the lowest thrust and flap settings, common for longer runways to reduce impact and wear on engines, the memo stated.
It resulted in a “takeoff with 400 feet of usable takeoff distance remaining,” the FAA memo concluded. A typical commercial airliner is traveling at 184 mph at liftoff, meaning the plane had about 1.5 seconds before reaching the end of the SFO runway.
After the incident, the airline reconfigured its planes’ computer systems, such as removing the slowest takeoff speed as an option at SFO.
That seems like a relevant change to highlight to the judge--which we will do as Round 2 of the complaints take place in Redwood City on November 5th.
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