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ATL Airspace vs. NYC Airspace

Posted: Sun Sep 01, 2019 2:36 am
by SuseJ772
I was reviewing some charts this evening and noticed that ATL Class B goes all the way up to 12,500. This seemed high as I thought most ended at 10,000.

So I checked to see what NYC was thinking it may be 12,500 under the assumption that the "super busy" Class-B's may now go up to 12,500. To my surprise NYC ends at 7,000 - which seems remarkably low even for a "small Class-B" like Kansas City let alone NYC. The fact I could take a Cirrus at 7,500 directly through all of NYC airspace seems pretty nuts.

Even DC ends at 10,000, and yes I know they have the SFRA and FRZ up to 17,999, but the fact ATL is more restrictive than parts of DC (i.e. west of IAD) also seems out of balance.

I know ATL is the busiest airport, but it certainly isn't the busiest market (NYC for sure has more traffic in and out of it than ATL).

So three questions really.

1) Why is ATL so high?

2) Why is NYC so low?

3) What determines the max height of Class B for any market?

Re: ATL Airspace vs. NYC Airspace

Posted: Sun Sep 01, 2019 2:46 am
by GalaxyFlyer
My guess, NYC was the first Terminal Control Area, now Class B, and was rather controversial at the time, so the top was low and never changed. ATL was no long after and they learned that higher was needed. Height is determined by ATC experience and Flight Standards. Lots of public comment. It’s not by regulation.

GF

Re: ATL Airspace vs. NYC Airspace

Posted: Sun Sep 01, 2019 3:42 am
by SoCalPilot
While most Class Bravo's go up to 10K, NYC and ATL aren't the only ones who are different:

- MIA goes to just 7,000
- DEN to 12,000 (makes sense given the elevation there)
- SLC to 12,000 (again, makes sense given the elevation)
- DFW goes to 11,000
- CLE to 8,000
- MSY to 7,000
- PHX to 9,000
- STL at 8,000

It all has to do with airspace analysis and the traffic routes/patterns in and out of the airspace. If the FAA thought that New York, New Orleans, or Phoenix needed their Class Bravo's to top out at 10,000, they would.

Re: ATL Airspace vs. NYC Airspace

Posted: Sun Sep 01, 2019 1:33 pm
by spacecadet
Airspace around the country is under constant analysis. If NYC's class B is still at 7,000, then there is some continuing reason for it.

Looking at the two areas, I think the main thing is that NYC and the surrounding area is pretty much blanketed by Class E airspace down to 700 ft AGL, so that area above the Class B is still controlled airspace all the way up to 60,000 ft.

In ATL, there are a lot of gaps in the Class E airspace, so there's actually *less* controlled airspace even though the Class B tops are higher. The B tops have to be higher for that reason - otherwise that airspace would be totally uncontrolled.

There's also about a 1,000 ft. difference in the elevation of the airport and surrounding terrain, so you'd expect ATL to have slightly higher tops even without the gaps in E airspace. But most of it I think is explained by the Class E.

The real question is why is so much airspace around ATL uncontrolled.

Re: ATL Airspace vs. NYC Airspace

Posted: Sun Sep 01, 2019 8:21 pm
by timz
spacecadet wrote:
that area above the Class B is still controlled airspace all the way up to 60,000 ft.

Which doesn't mean you need permission to enter it.

Re: ATL Airspace vs. NYC Airspace

Posted: Sun Sep 01, 2019 9:03 pm
by GalaxyFlyer
Class E is not uncontrolled airspace, so there’s a hole in your argument. Uncontrolled means Class G or Class F. Class F isn’t used in the US.

GF

Re: ATL Airspace vs. NYC Airspace

Posted: Mon Sep 02, 2019 2:33 am
by bomber996
spacecadet wrote:
Airspace around the country is under constant analysis. If NYC's class B is still at 7,000, then there is some continuing reason for it.

Looking at the two areas, I think the main thing is that NYC and the surrounding area is pretty much blanketed by Class E airspace down to 700 ft AGL, so that area above the Class B is still controlled airspace all the way up to 60,000 ft. :duck:

In ATL, there are a lot of gaps in the Class E airspace, so there's actually *less* controlled airspace even though the Class B tops are higher. The B tops have to be higher for that reason - otherwise that airspace would be totally uncontrolled.

There's also about a 1,000 ft. difference in the elevation of the airport and surrounding terrain, so you'd expect ATL to have slightly higher tops even without the gaps in E airspace. But most of it I think is explained by the Class E.

The real question is why is so much airspace around ATL uncontrolled.


I just checked the chart and maybe I'm not seeing what you're seeing? While yes, there is less of an area indicating Class G only to 700' AGL, that just means that Class G goes to 1200' AGL. It's still Class E above the Class G until the overlying Class B. It's not THAT much more uncontrolled airspace.

While the Class B will typically go up to 10,000' MSL, it doesn't always have to. Each Class B is designed as needed for the specific situation it is designed to control. Not every one is the same size, or dimensions like your typical Class C or D.

Also, Class E overlies Class A, so technically there is no end to controlled airspace above ATL. :duck:

Peace :box:

Re: ATL Airspace vs. NYC Airspace

Posted: Tue Sep 03, 2019 1:29 am
by luckyone
Asking out of sheer ignorance: does this have anything to do with the presence of Dobbins Air bass in Marietta and Robins just south of Macon?

Re: ATL Airspace vs. NYC Airspace

Posted: Tue Sep 03, 2019 2:54 am
by GalaxyFlyer
No, probably not. Dobbins isn’t that busy and Robins is a huge maintenance base, not that much flying.

Re: ATL Airspace vs. NYC Airspace

Posted: Tue Sep 03, 2019 10:43 am
by N1120A
As was said, airspace is constantly being evaluated and gets redesigned. The San Francisco Class B just got massively realigned about a year ago. A look at the design of the Los Angeles and San Diego Class Bs will tell you that the upside down cake design isn't a catch all. My guess is that the difference in altitudes has everything to do with the way the departures and arrivals work in the airspace, and also the way the airports are located. Terrain is certainly a factor in Denver and Salt Lake, but the difference between NYC and ATL can't be explained that way.

Re: ATL Airspace vs. NYC Airspace

Posted: Mon Sep 09, 2019 2:57 pm
by Cubsrule
N1120A wrote:
As was said, airspace is constantly being evaluated and gets redesigned. The San Francisco Class B just got massively realigned about a year ago. A look at the design of the Los Angeles and San Diego Class Bs will tell you that the upside down cake design isn't a catch all. My guess is that the difference in altitudes has everything to do with the way the departures and arrivals work in the airspace, and also the way the airports are located. Terrain is certainly a factor in Denver and Salt Lake, but the difference between NYC and ATL can't be explained that way.


I think you are right. In west flow, arrivals from the northwest (CHPPR1 arrival) and departures to the north (PADGT2 departure) cross around the fix RAINN. That's a point that it seems pretty clear ought to be in the B, and better performing aircraft (WN 73Gs, for instance) can be in the 8-10,000 feet range there.

Re: ATL Airspace vs. NYC Airspace

Posted: Mon Sep 09, 2019 11:46 pm
by zuckie13
Isn't it just the fact that in NYC you have all those airports so close together that they transition from the airport to NY TRACON in order to manage that? It's still highly controlled airspace, just not with the tower at the airport anymore?