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7 Answers

The shape of Class E airspace

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General Aviation

Take for example class E airspace around an airport that extends upwards from 700 feet above the surface (magenta fuzzy colored circle).

Sometimes this airspace does not form a perfect circle around an airport.  Oftentimes, one side is extended outwards.  Oftentimes, two sides are extended outwards.

I've been told this shape is due to approaches. 

However, can't one approach an airport/airspace from any side?  Therefore, how do they determine which side of the class E airspace (circle) to extend outwards on a map?

Also, some class E airspace starts at the surface.  What, specifically, would cause class E airspace surrounding an airport to begin at the surface?  Airports with more traffic...?

7 Answers

  1. Jonathan Katz on Jan 27, 2011

    A good example of this is KBMG, Bloomington, IN. Follow the URL below to see the chart on skyvector..
    It’s a class D airport with class E airspace around it, and some of it sticks out for an approach. Some of it starts at 700 AGL (dashed line) and some of it at 1200 AGL (solid magenta.) We have all the “goodies” here.
    In these terms, it’s an IFR approach to KBMG that creates the “extra” area of class E around the airport that sticks out like a fat dogleg. Although in the VFR world we can approach the airport from “any angle” when making the approach IFR, the airplane will circle around to a specific checkpoint (called an intersection) and then turn to a pre-determined heading that will lead the airplane directly to the runway. For obvious reasons this space needs to be class E– better visibility requirements than G are required so VFR pilots can see airplanes who are flying IFR.

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  2. Kent Shook on Jan 27, 2011

    It is called a transition area (see AIM 3-2-6e.3) and does exist due to approaches, but as with the lower class E space existing in the first place, it is due to *instrument* approaches. Airports that do not have any instrument approaches will not have the lowered class E around them (Example – KHBW, Hillsboro, WI. Punch this into SkyVector.com if you don’t have a Chicago sectional chart).
    AIM 3-2-6 also says that the class E airspace that starts at the surface is designed to contain all instrument procedures. For example, KAMW (Ames, IA) and KLNR (Lone Rock, WI) are uncontrolled fields that have ILS approaches, which allow airplanes to fly in instrument conditions as low as 200 feet off the ground, so the 700-foot transition zones are not low enough to contain the entire approach. Those airports have class E airspace all the way to the surface.

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  3. Kent Shook on Jan 27, 2011

    One other thing I should mention – Airspace changes don’t automatically follow when procedures are changed or airports are closed, sadly – You can see the “ghosts” of airports in some spots on the chart. For example, if you punch in KVUO or KPDX, you’ll see that the Portland, OR class C airspace has a cutout for an airport that no longer exists. Another example is just southeast of KACY, where just to the southeast you can see both a transition area and a class E surface area for the now-closed Bader Field.

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  4. Stuart Stein on Jan 27, 2011

    KVUO is Pearson Field in Vancouver, Wa and does exist and is active, http://www.airnav.com/airport/KVUO. Have flown out of there myself.

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  5. Jason Schappert on Jan 27, 2011

    You’re correct to say it’s made for approaches
    Think of it like this…
    The VFR cloud and visibility requirements in class G airspace are? 1 mile and clear of clouds!
    That’s nuts! Do you really want someone goofing around in 1 mile and clear of clouds when you’re shooting an approach? No!
    So thus they’ve created these transition and surface class Echo areas making the VFR requirements our standard 3 miles and 1-5-2 (1,000 above, 500 below, and 2000 horiz from the clouds)
    I did a great video explaining all of this in better detail below

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  6. John Doe on Jan 27, 2011

    Thank you!  Great stuff!  Since I am a student pilot working on VFR, some of the “instrument procedures” allude me at this point.
    Great information!

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  7. Kent Shook on Jan 27, 2011

    I didn’t say KVUO was closed, just that it’s one of the identifiers that you can type into skyvector so that you can see the cutout on the northeast side of the PDX class C for a different airport that doesn’t exist any more.
    After some research, the field that was there was Evergreen (59S). Now, just a hole in the Charlie. 🙁

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