Please Don’t Use the Whole Length of the Bay

As some of you may know, proposals from the mid-pen coalition (MPC), Palo Alto Sky Posse (PASP), and the City of Palo Alto (CoPA) all contain elements of “use the whole length of the bay”.

Throughout this year, while talking to residents in Palo Alto and Mid Peninsula in general, very few were aware of the details or consequences of these proposals, since the proposals were generally either unpublished or vaguely phrased. Neither MPC nor PASP published maps or anything equivalent to our “community impact matrices” that show which communities are affected by the proposals.

Below, I convert the verbiage from these proposals to simple maps, and identify the communities affected. (Original CoPA proposal, for reference)

bay10Key to understanding the ramifications of “down the bay” is the SJC departure pattern called LOUPE, shown on the right. LOUPE is a spiral, and occupies all altitudes between ground level and 15,000’.

This means that it is “impenetrable” to other traffic, and so limits how much benefit can be derived from continuing down the ILS path. LOUPE is a noise-abatement track that helps traffic remain over the industrial parts of San Jose during departures.

The LOUPE handles most of SJC’s departures on “normal flow” days, with southbound departures only performing a “half-Loupe” after taking off.

bay20Below is a map depicting CoPA proposal #1 (which is detailed in EndNote 3) – a direct line from waypoint EDDYY to the SFO ILS path (Magenta). The chart shows the path going to waypoint WETOR, which is what the consultant was describing during the Palo Alto city meeting, and according to it, traffic will cross into residential areas at altitudes starting at 6000’. (A less aggressive detour is shown dashed, which would be flown at 5000’)

Without a doubt, 6000’ is better than 4000’ but not by as much as you’d think – the difference would be about 3.5 dB. Not chump change, but certainly not “no impact”. In fact, 6000’ is about what Los Altos Hills is seeing today with SERFR, and they are certainly not happy about it.

I have said before about this plan: If we were designing the airspace from scratch, with no regard to history, then this might not be a bad way to go. (Though if we had the freedom to do this, there are other ideas that would be possible too.)

But we’re not. History exist, and moving a flight path to a new set of people, even if you’re absolutely certain that it serves universal justice, is wrong. It is also exactly how we got into this mess to begin with. The FAA thought that “if we just move SERFR by 4 miles… what harm can it do?”

To those still tempted, I’ll remind that Mountain View and Sunnyvale are already burdened with flights into SJC at 2000’ (yes, you’ve read that right) on “opposite flow” days, which are relatively frequent at SJC. And when they do, it’s the entire throughput of SJC that overflies them, not just a fraction. I encourage you to visit Sunnyvale during such an “opposite day”. It’s eye opening.

It is ironic that Palo Alto, who has lead the charge of labeling QSNC’s request to undo the ground track shift as “merely moving noise onto others”, has produced a list of proposals that is based on moving noise unto others.

PASP’s response to the FAA’s feasibility study was: “Once again, the FAA chose to move noise for some communities, …”, which is especially poignant since PASP has also rejected any solution that raises MENLO over their own skies. I also doubt that Palo Alto would be enthusiastic if Sunnyvale proposed to move those 2000’ SJC arrivals over to Palo Alto, in order to “use the whole length of the bay”.

It is also ironic that MPC, who expresses such fear and doubt about OPD arrivals over the BSUR flight path (at 6000’ – yes, the same altitude) has no similar fears about OPD over the SERFR path or over this proposed “Sunnyvale” path.

By proposing these plans, MPC and Palo Alto are invalidating their principled stand against restoring the flight path. If it’s ok by them to lobby for what they’re proposing, then they have no business raising objections to a restoration of a ground track that should never have been moved. You’ll note that they are not even demanding in their plan that the FAA commit to the same (impossible) criteria that they’ve asked for with respect to the SERFR/BSUR restoration.

To repeat the obvious: The logic of “move it elsewhere” is self-defeating. It never ends. Flight paths should not have been changed, and they need to be put back. Beyond that, things that got broken (like the implementation of OPD) need to be fixed – but not punted over to other towns. It’s as simple as that.

CoPA Proposal #2 is more ambitious, taking SERFR traffic over Milpitas and the “back” side of SJC. Flight altitudes over residential areas are now 7500’ when flown nominally – higher, but this is still not a “zero impact” solution.


From the FAA’s standpoint, this proposal changes the entry point into the Metroplex, which IMO will require re-doing the high-altitude paths between LA, PHX, and SFO.

The arrival routes (DYMND and YOSEM) are already seeing 260 flights/day (The entire eastern seaboard and hubs such as Denver), and merging the 160 flight/day of SERFR into them so late will likely create a large “vectoring cloud” similar to what we see today over the Santa Cruz mountains and mid-peninsula. (Currently, DYMND flights are merged in as much as 100 miles upstream, so there’s relatively little vectoring going on.)

But – this is all for the FAA to decide. All we can say is that this is a much longer term proposition, and so even if the FAA agrees to take this under consideration, it is years away, and we need to fix SERFR first.

From a community standpoint, however, the same issue stands as before: this proposal is overflying Milpitas, and Milpitas is not in the room discussing it.

Even though the flights are at 7500’, vectored flight will result in non idle-power descents, and will have an impact.

Even when we propose restoring the SERFR flight path to what it was last year, and even when flight altitudes over Santa Cruz are ~13,000’, we still have a representative from Santa Cruz in the room, and we still need to ask him to be gracious about it. So proposing this to a body that does not represent Milpitas is wrong.

For context, when we confronted Palo Alto Sky Posse (about half a year ago) about their plans to move traffic over a different city, their answer was that the city residents do not have to be brought into the discussion because “they have no standing in the matter”. By that logic – how does Palo Alto, or for that matter, any resident, have any “standing”?

To recap, regarding flight altitudes, this is what we’ve learned about noise impacts so far: (Note all altitudes are “above ground level”, or AGL)

  • Idle power flight above 10,000’ AGL, directly overhead, over light-urban areas, is generally harmless. This is evidenced by having no impact over Santa Cruz and Scotts Valley during BIG SUR’s existence.
  • Idle power flight above 10,000’ AGL, offset by 1-3 miles, over rural areas, is also generally harmless. This is evidenced by having no impact over SLV during BIG SUR’s existence.
  • Idle power flight, at 8000’-10,000’ AGL, directly overhead, over rural areas, seems to be ok, based on testimony of mountain residents that live under the BSUR path. However, we don’t have a wide statistical basis for that.
  • Powered level flight above 10,000’ AGL, directly overhead, over light-urban areas, has a moderate impact. This is evidenced by the current impact over Capitola.
  • Powered level flight at 10,000’ AGL, directly overhead, over rural areas, is highly disturbing. This is evidenced by the high impact over the “Happy Valley Corridor”.
  • Powered level flight at 6000’ AGL and below, directly overhead, has a harsh impact, as evidenced by Summit and the mid-pen area.
  • Departing flights, at or below 20,000’ over rural areas has a strong impact, and is surprisingly sensitive to the ground track location, suggesting the effect is amplified by mountainous environments. This is evidenced by impact on the Summit area.


By “Idle power flight” we mean “flight procedures that mostly use idle power”. In reality, except for very few flights, most flights will use some small amount of power to tweak the trajectory, in response to things like variable winds.

Even under OPD, absolute idle power the entire way is a goal, not a guarantee. However, this has always been the case, even for BIG SUR arrivals. With OPD, this is a central driving goal, so it reduces such power application to a minimum.

Addendum: various plans by PASP and MPC from the last year.

Below are more detailed maps by PASP and MPC. These maps never made it to the groups’ websites, and very few of their supporters were aware of them.

1: Palo Alto Sky Posse’s plan, presented to the City of Palo Alto a few month before NextGen even happened:


The slide shows the same “down the bay” arrival (in the inset picture) with a proposed route, in yellow, replacing BIG SUR and essentially transferring all traffic to Sunnyvale (and Ironically, to Happy Valley and Summit)

Once we discovered this deck, PASP stopped using this slide, and only used the preamble slide – conveniently ignoring (and cropping out) the affected communities.


In turn, this was  changed into the sanitized text: “use the whole length of the bay” and even this slide is no longer used, but the plan never changed.

2: This slide from MPC (Specifically, Sky Posse Los Altos) is only about a month old, and depicts another variant of the “down the bay” concept, this time going from SWELS to ROKME, overflying Mountain View at 5000’


Needless to say, the altitudes proposed for Mountain View (~5000’) are even lower than SERFR altitudes at Los Altos.