A multi-city and county committee tasked with finding ways to reduce overhead noise from airplanes going to and from San Francisco International Airport has released preliminary proposed recommendations.

The 12-member Select Committee on South Bay Arrivals has considered multiple suggestions from the Federal Aviation Administration (FAA), community groups and professionals since first convening in March at the invitation of U.S. Reps. Anna Eshoo, Sam Farr and Jackie Speier.

Residents in Santa Clara, San Mateo and Santa Cruz counties have been affected by the increase in flights and noise since the FAA rolled out a new nationwide air traffic program, NextGen, which was mandated by Congress to make the nation's aviation network more efficient. The Bay Area launched NextGen routes in March 2015, to the consternation of many residents -- particularly in Palo Alto, over which three flight paths converge before heading to SFO.

The Select Committee, which is chaired by Santa Clara County Supervisor Joe Simitian, was cautious in formulating potential recommendations, stressing that the 34-page document is a working paper and that the committee had not yet made recommendations; these are only proposed.

The path to making recommendations to the FAA has been contentious, with communities at times in vocal opposition to each other's proposals. In some areas of concern, the committee did not yet commit to a recommendation, instead choosing to identify the things they could agree on and leave open for discussion those where consensus is not yet reached.

The public will have a chance to weigh in on Oct. 27, when the committee will hold a public comment hearing from 1 to 4 p.m. at the Palo Alto City Council Chambers.

The committee's ideas fall into three categories: Those based on the FAA's proposals; the public's proposals ("other potential solutions"), and longer-term issues. Below are summaries of key parts of the document and possible recommendations most likely to impact Palo Alto, East Palo Alto, Mountain View and Menlo Park.

The FAA proposals:

Change restricted airspace around SFO

The Committee would recommend changing the shape of the restricted airspace around SFO, known as Class B airspace, which is designed to ensure a higher level of safety for arriving aircraft.

The FAA proposed altering the size or shape of the airspace so that pilots wouldn't need to use altitude and speed adjustments to stay in the prescribed zone.

Currently the airspace parameters forces planes arriving from the south over the Santa Cruz Mountains to have to“level off” to stay within the airspace. That requires aircraft to use speed brakes, increase thrust, and other methods that create greater noise. Communities most affected include near Capitola and the Midpeninsula.

Move the southern arrival flight path to the west, near the former Big Sur route

The Committee has not yet determined if it will recommend the alternative.

NextGen moved the flight path of planes arriving from the south at SFO more to the east, putting aircraft over some coastal residents in the Santa Cruz area who had not previously been in the flight path. NextGen removed a flight path called Big Sur. The proposed route, DAVYJ, would be similar to the Big Sur track: roughly 3-4 miles to the west of the current flight path, which is near the Santa Cruz County coastline near Capitola.

But DAVYJ, while strongly favored by some Santa Cruz County residents, is also widely opposed by many Midpeninsula residents. They point out that the FAA's own data show that decibel levels would greatly increase for many Midpeninsula residents living in the most densely populated areas, and the higher noise levels would occur over a longer swath, particularly over Palo Alto, East Palo Alto and parts of Mountain View.

Other potential solutions

Higher altitudes over MENLO waypoint

The designated point over which all of the planes from the south must pass, the MENLO waypoint, is located several city blocks south of the intersection of Willow Road and Highway 101. Planes currently cross at 4,000 feet, although by an agreement arranged more than a decade ago through Eshoo and then-Palo Alto Mayor Gary Fazzino, planes were supposed to fly no lower than 5,000 feet.

The Committee would recommend planes fly at a higher altitude at the MENLO waypoint and that the FAA assess if a different waypoint would be feasible. The committee noted it does not recommend that a different waypoint be established if it results in shifting noise to other communities.

The City of Palo Alto, which hired consultants Freytag & Associates to study the problem, suggested that a new waypoint should be located to the east and/or north of MENLO, presumably over a less populated area and at a higher altitude. Other existing waypoints located in San Francisco Bay just to the north and south of the eastern shoreline of the Dumbarton Bridge might be used. Planes crossing at these Bay waypoints would be at a higher altitude.

In June 2016, an average of 183 aircraft crossed each day over this waypoint, representing 30 percent of the arrivals into SFO over one of the Peninsula's most populated areas, according to the FAA. Currently 50 percent of the aircraft on the path are "vectored" prior to the MENLO waypoint, causing additional low-altitude noise and air traffic over these communities.

Increase altitudes and how planes descend into SFO

The Select Committee would recommend that planes come in at a slightly steeper approach that would allow them to begin their descent at a higher altitude, which would reduce noise. The committee would also recommend that, to the greatest extent possible, while still ensuring the safety of the aircraft, that the altitude be increased for all flight paths in and out of SFO.

Retrofit certain planes with wake vortex generators to reduce noise

The Committee would recommend retrofitting a certain class of aircraft, the Airbus A320 built before 2014, with wake vortex generators to reduce noise.

Airbus A320 aircraft built before 2014 make a whistling or whining sound on approach due to the design of the wing. The whine can be reduced by mounting a small air deflector on each wing. The technology reportedly costs $3,000-$5,000 per plane. The noise reduction is claimed to be two to 11 decibels, depending on flight factors. Roughly 35 percent of the aircraft arriving and departing SFO need the retrofit.

Shift northern arrivals to the Bodega "East" leg

Planes arriving from the north currently use the Bodega path, in which planes reach a point roughly over Daly City and continue south flying past SFO, using either the Peninsula (the so-called West leg) or San Francisco Bay (the East leg), to make a U-turn for landing on two runways. The Bodega East leg shares the final approach path into SFO with aircraft arriving from the east.

The Committee would recommend greater use of the Bodega East leg for planes. From 11 p.m. to 6 a.m., when air traffic is lighter, virtually all such aircraft should come in using the San Francisco Bay approach, the committee is proposing.

Planes using the East leg create a dramatically lesser noise impact versus aircraft using the West leg, which flies over the highly populated Midpeninsula, and particularly Palo Alto. Air traffic was almost evenly split between the two legs, but in May 2016 roughly 70 percent of the arriving aircraft began flying over the Midpeninsula.

Redirect southern arrivals to an eastern approach into SFO

The Committee has not endorsed this solution

SERFR is a southern arrival path into SFO approaching from the south over the Santa Cruz Mountains. Flights on the path include aircraft from the southwest, such as Phoenix and Houston.

The City of Palo Alto suggested in its Oct. 10 consultant's report that the aircraft from the southwest should removed and use an eastern approach into SFO. Aircraft would either use an existing arrival procedure used for flights arriving at SFO from the east with a flight path that enters the Bay roughly between Milpitas and San Jose, or use a new procedure, which is located at the intersection of Hostetter Road and Morrill Avenue, east of Interstate 680 in East San Jose.

The FAA said this proposed solution raises a number of potential concerns. In June 2016, the first suggested route already carried the greatest percentage of daily air traffic into SFO, an average of 253 aircraft per day, or 41 percent of the arriving traffic. The procedure also shares the final approach path into the airport with aircraft arriving from the north on the Bodega procedure), specifically the 30 percent of Bodega arrivals on the East leg.

The FAA has also said that using the new route potentially conflicts with departures out of San Jose International Airport and moves existing noise to another community. But the existence of an overnight curfew at San Jose International Airport might accommodate a new procedure using the new waypoint as a potential solution in the overnight hours. The FAA may, therefore, want to examine whether this proposed solution, or a variation thereof, could be effectively implemented without shifting noise.

Enforce 8,000 foot minimum over Woodside navigational beacon

In July 1998, a procedure was instituted that required flights over the Woodside navigational beacon to be no lower than 8,000 feet above sea level, “traffic permitting.”

The Select Committee would recommend that planes comply with the 8,000-foot altitude, traffic permitting. The altitude restriction would also apply to all vectored flights in the Woodside beacon area. Further restrictions would prohibit any overnight crossings at Woodside below 8,000 feet.

Numerous reports from the community claim the planes are currently not honoring the 1998 agreement and are flying at much lower altitudes including at night when residents are particularly sensitive to noise. Some flights are allowed to come in at 6,000 feet over this point, including overnight. An estimated 36 percent of Oceanic flights arriving at SFO between 1 a.m. and 6 a.m. fly over the Woodside point.

Develop new rules for overnight flights

The Committee would recommend that the FAA, SFO, and industry users work to establish new, additional overnight noise-abatement procedures within the next six months.

Flights are considerably reduced during night hours starting at 11 p.m., and there is considerable potential for aircraft to be rerouted over the San Francisco Bay and Pacific Ocean, instead of the Peninsula, the committee noted.

Modify where aircraft can vector

The Committee would recommend that the FAA identify locations with the most compatible land uses for vectoring, which involves turning aircraft off the assigned procedure or flight path. To vector, air-traffic-control gives orders to change speed, make a turn or alter altitude, which can cause increased noise.

New vector locations could be over the Pacific Ocean or San Francisco Bay.

Vectoring is common over Menlo Park, East Palo Alto, Palo Alto and Mountain View from east (Oceanic), north (Bodega) and south-arriving flights. Roughly 50 percent of the arrivals from the south are currently vectored so they will be sequenced and spaced properly for arrival.

If the pilot is not given a speed or altitude restriction by air-traffic control, it is unlikely that noise will result, according to the committee.

Modify arrival procedure into San Jose International Airport

The Committee has not determined a potential recommendation.

The northern arrival path into San Jose International Airport, called BRIXX, runs down the Peninsula, roughly over La Honda and Boulder Creek before turning and flying south and then east and north for a final approach. The path intersects with the southern-arrival path (SERFR) going to SFO.

Under NextGen, the arrival path became more concentrated; with vectoring moving southward. About 76 percent of the BRIXX flights are vectored or turned off the flight path prior to the point where the two flight paths intersect. These changes resulted in complaints from residents in affected areas.

Suggestions have included moving the intersection of the two flight paths farther to the north and east, potentially over the Rancho San Antonio Open Space Preserve; and increasing the altitude of the San Jose flight path so that it is above the altitude of the southern flight arrival path. But the FAA said that could move noise further into the Midpeninsula area already being impacted.

Longer-term issues

Any recommendation from the committee should not be deemed to end the discussion, or the problems. The Select Committee may also recommend establishing a permanent committee to address regional aircraft noise issues. That organization would be an adjunct committee of one of the existing community roundtables at either the San Francisco or Oakland International airports. It could include a new, independent commission devoted to airport noise or and other airport issues, and it would continue the work done by the Select Committee.

The committee also recommended noise-measurement modifications that would more accurately take into account the noise experienced by people on the ground. Noise levels currently are taken cumulatively within a 24-hour period and don't accurately measure the true impact experienced by residents.

The committee would recommend that the U.S. Congress require the FAA to adopt the new measurements. The FAA should also monitor and document noise exposure of any proposed solutions before and after they are put in place so there is a measurement of how well they are working.

The complete draft "Report of the Select Committee on South Bay Arrivals" may be viewed here.

The City of Palo Alto's recommendations can be viewed here.