I was asked recently if the changes to the airspace are Good or Bad to Culver City. My answer, which we discussed at the last Culver City meeting about NextGen impacts, is “Yes, No, and We won’t know until its implemented”. The FAA has a summary of potential benefits for the entire airspace and Culver City’s changes would be a subset of those. The changes are not without precedent- Other communities have undergone a NextGen implementation and we can use their experience about what to expect.
A petition called “Stop the FAA NextGen Flights Over Culver City” cites many examples but doesn’t offer the full perspective of the potentially subtle issues of the FAA proposed implementation. Hopefully this can help inform people about what to comment about if they choose to sign that.
From a noise perspective there are no benefits, only negatives: The proposal shifts noise around [ Noise mapping ] in the areas that have noise above 45 dB DNL and increases noise in softer areas [ Noise impacts by Population ]. We cant’ even answer whether the City of Culver City has a net gain or loss of noise (note: the FAA released on 9/1/2015 the source data for the noise analysis – it will take time to analyze to find this result). The noise modeling itself has faulty components [ various comments ] and the pollution conclusions are purely theoretical.
There isn’t a rigid flight path over Culver City. LAX arrivals fly over Santa Monica Airport at 7000-8000 ft. After Santa Monica the pilots are given the instruction by Air Traffic Control to “maintain heading and descend to” either “4000”, “2600”, “2500 ft”. IRNMN. CRDHR. HUULL provide a fixed, and precise flight path.
My earlier post described how the flight paths may change [ Culver City Flight Paths ] and a potential issue [ Proposed flight path undermines LAX noise Abatement efforts ] with over-ocean operations. These would be a good primer for the discussion below.
Here is just a short breakdown of Pros and Cons just for changes over Culver City:
- The use of RNAV and Optimized profile descent (OPD) will mean that the planes will be following a more formal descent which will reduce the range of pilot chosen descent options. Possibly there will be reduced noise causing operations such as flaps and power-downs. On average the heights may be near the same but the range of higher and lower elevations will be slightly reduced.
- RNAV to the DAHJR waypoint, and RNP to the airport, will reduce the spread of airplanes farther away from the flight path- reducing noise. The spread wasn’t so wide to begin with, due to flights having to cross at SMO, so the difference won’t be as severe as when RNAV was rolled out other places. The concentration of flights are currently within 3/4 mile so narrowing into 1 /3 of a mile will only save ~ .2-.4 dB from outside the path. Other communities start with paths miles wide.
- It’s only going to initially effect 30-40% of the flights*. The same variance will still be happening just at a slightly smaller scale. Over time the nonconforming flights will reduce as the fleets get replaced/upgraded and crew trained.
- There may/or may not be a reduction in emissions / fuel use by the shortened and lowered BIGBR flight path. There is a potential of savings by the Optimized Profile Descent but that’s indeterminate until we see how the planes fly the OPD.
- When comparing against doing no changes, The FAA’s Environmental Assessment(EA) models a decrease of 0.0-0.02 dB DNL* directly under the proposed daytime flight path, and -0.4 dB DNL* decrease directly under the proposed, and lowered, late-night flight path BIGBR.
- It’s never a good idea for people under a distributed flight path to have the path narrowing above them via a single-path RNAV or RNP. It’s a concentration of noise and pollution over a smaller population that runs against environmental justice. The residents of Pheonix, Boston, Santa Cruz, Palo Alto and other communities across the country attest that living under a RNAV/RNP proposed flight path is going to have significant effects on quality of life.
- Optimized profile descent (OPD) with a flight path dictated rate of descent doesn’t work with same efficiency for all planes. One of the claims in Palo Alto’s suit is that OPD is increasing noise as planes have to flutter power, keep partial power on or engage in more side-side drift instead of a reduced power coast-down. The FAA is betting a large part of the sound analysis results on OPD’s reducing sound above 6000ft.
- The DNL* metric is used more as a measurement of expected annoyance than as a real noise metric. The averaging over the day occludes the real way we hear airplane noise- one plane at a time. A metric such as N60 or N70 ( number of airplane-related noise events over 60 or 70dB ) is a far better predictor of impacts. This data has not been released by the EA. [ Supplemental noise metrics can help public understand changes ]
- There will be more noise from the BIGBR flight path. The midnight-6:30am over ocean flight path and eastern operation flight paths are combined into one flight path. The crossing at Santa Monica’s CLIFY has dropped from 8k to 7k. The closer movement of the immediately prior waypoint [DOWNE to TOMY] means planes will overfly Culver City between 1k-800ft less. This flight path won’t be using OPD.
- If the flights over downtown Culver City are going to suspend their power-downs, flap dropping and other noise making operations until out of the RNAV at the DAHJR waypoint, that same noise will happen further east at a lower altitude. It will be worse for somebody. These specific noises are not modeled separately in the analysis.
- The flight paths have shifted slightly northward so the noise footprint will include communities that didn’t have it bad before.
- Overall the Proposed action uses .33% more fuel than without it. Emissions will increase from the Proposed action as well. The amount of fuel saving/waste for the tracks over Culver City hasn’t been itemized.
- It’s only going to initially effect 30-40% of the flights. Overtime it may include almost all. According to the FAA study team, 90% of LAX arriving aircraft is capable of RNAV.
Planes are progressively getting larger and quieter but the emissions aren’t going away. Air traffic hasn’t returned to the pre September 11th values so an increase in traffic is to be expected.
One of the complaints against the FAA is the process. Community input wasn’t invited during the design process and the results of changes are not readily understandable. The metric used to describe noise level is DNL [ Supplemental noise metrics can help public understand changes ] which tells nothing about the loudness of each plane or how many times it flies over.
The Environmental Assessment(EA) is not intended to be a rigorous process as it is performed in lieu of an Environmental Impact Report(EIR). It’s purpose is to prove the assertion that there will be no significant impacts and a more rigorous EIR is not needed.