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This question specifically is about non-towered airports surrounded by round circles of E2 airspace, with one or more "extensions" of E4 airspace that abut the E2 airspace. Therefore it is not the same as the related question that may be noted above. Also the question noted above is about how certain airspace functions when the tower is open versus closed, not about why it is drawn a certain way on the sectional chart.

Note that this configuration-- a non-towered airport surrounded by a round circle of E2 airspace, with one or more "extensions" of E4 airspace that abut the E2 airspace -- is a somewhat unusual airspace configuration. In the vast majority of cases where a non-towered airport is surrounded by Class-E-to-surface airspace that has one or more rectangular projections, the entire Class-E-to-surface airspace is designated as E2 airspace. No E4 "extensions" are designated. Examples: KONP, KSHR. This question is not about that airspace configuration.


The question:

According to the FAA's "Airspace Designations and Reporting Points" document Order 7400.11C ( https://www.faa.gov/documentLibrary/media/Order/JO_7400.11C.pdf ) , KACV, KTLV, KSGU, KBIH, and KTPL all share the same airspace configuration: a round E2 circle around the airport, with one or more E4 "extensions".

Why then on the aeronautical sectional charts is the Class-E-to-surface airspace near KACV and KTLV depicted differently than the Class-E-to-surface airspace near KSGU, KBIH, and KTPL?

The first two are depicted with a dashed magenta circle going all the way around the airport, while the last three are not. In the case of the last three the charts give the impression that all the Class-E-to-surface near the airport may be E2, with no E4 "extensions".

KACV: California Redwood Coast Humboldt County near Arcata -- http://vfrmap.com/?type=vfrc&lat=40.978&lon=-124.108&zoom=10

E2 described on page E-127 of the "Airspace Designations and Reporting Points" document, E4 described on page E-211

KTLV South Lake Tahoe -- http://vfrmap.com/?type=vfrc&lat=38.894&lon=-119.995&zoom=10

E2 described on page E-135, E4 described on page E-220

KSGU -- St. George Regional Airport, UT -- http://vfrmap.com/?type=vfrc&lat=37.036&lon=-113.510&zoom=10

E2 described on p. E-84, E4 described on p. E-190

KBIH -- Bishop Airport, Bishop CA -- http://vfrmap.com/?type=vfrc&lat=37.373&lon=-118.364&zoom=10

E2 described on p. E-130, E4 described on p. E-211-212

KTPL -- Temple, Draughon-Miller Central Texas Regional Airport, TX -- http://vfrmap.com/?type=vfrc&lat=31.152&lon=-97.408&zoom=10

E2 described on on p. E-127, E4 described on p. E-209

It seems that it would be good for the chartmakers to standardize on the notation used at KACV and KTLV rather than the notation used at KSGU, KTPL, and KBIH, since there appear to be some functional differences between the E2 and E4 airspaces, as explored in the related question linked below.

Related question with links to additional related content -- What is the primary reason that the non-towered airports KACV and KTLV have E4 extensions to E2 airspace?

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  • $\begingroup$ Dashed Class E is about protecting approaches. $\endgroup$ – Juan Jimenez May 7 at 15:34
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    $\begingroup$ It's not a duplicate because KEGE is a towered airport and towered airports almost always have a different configuration to the Class-E-to-surface airspace than KEGE. KEGE is an oddball and doesn't really shed light on the present question $\endgroup$ – quiet flyer May 7 at 18:57
  • $\begingroup$ Class E is not about tower/no-tower. KEGE has a precision approach and that is what the Class E protects. $\endgroup$ – Juan Jimenez May 8 at 8:15
  • $\begingroup$ Right but the Class-E-to-surface airspace is designated exactly the same at all 5 airports listed here so why the difference in depiction on the maps? None of them have towers. $\endgroup$ – quiet flyer May 8 at 14:14
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It looks like the answer is "it's a mistake or inconsistency in the sectional charts". Whether or not it's an outright mistake is debatable, but it certainly appears to be an inconsistency, and one can argue that the depiction used for KACV and KTLV provides some useful information that the depiction used for KSGU, KBIH, and KTPL does not.

It is the case that at KTLV-- but not at KACV or the other 3 airports mentioned here-- the description of the E4 airspace in the "Airspace Designations and Reporting Points" document has a note to see the A/FD for effective hours, while the E2 airspace has no such note. The sectional chart has a similar notation, with an arrow pointing specifically to the E4 airspace. (It also is the case that the current A/FD entry for KTLV simply reads "Airspace: Class E".) It seems possible that the policy of the charting agency is to depict the adjoined E2 and E4 Class-E-to-surface areas as two distinct areas in any case where there is a possibility why their effective hours may be different. If this is true, it doesn't explain why that style of depiction was also used for KACV.

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  • $\begingroup$ Yes, I answered my own question, but any other insights are most welcome. s $\endgroup$ – quiet flyer May 8 at 0:47
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If the bumpout is fully enclosed by the magenta line, then it is part of the "Class E airspace designated for an airport". If it is truly an extension, then it is outside the main circle (which is usually a Class D or higher, but can be Class E) and is not part of the Class E airspace designated for the airport. Extensions have different rules for when they revert down to Class G, and different rules for special VFR and whether UAS need permission to fly in them (they don't). Big topic of discussion in the drone world.

http://goldsealgroundschool.com/uav-library/surface-E-authorizations.pdf

EDIT: there does appear to be a conflict between the charts and docs on this one. Not the first time...

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  • $\begingroup$ What you wrote in your answer is exactly what is the normal practice and exactly what I thought was always the case until about a week ago. However, if you look closely at the "Airspace Designations and Reporting Points" document linked in the question, you'll find that at KSGU, KBIH, and KTPL, the airspace in the rectangular parts of the Class-E-to-surface airspace is actually designated as E4 not E2, even though it is FULLY ENCLOSED by the very same magenta line that encloses the airport, with no separation. If you go look at the FAA interactive sUAS map you'll see you need no (ctd) $\endgroup$ – quiet flyer May 7 at 19:57
  • $\begingroup$ (Continuing) If you go look at the FAA interactive sUAS map ( faa.maps.arcgis.com/apps/webappviewer/… ) you'll see you need no special permission to fly in the part of the Class-E-to-surface that in the rectangular part of the shape at these three airports, even though you'd never know it by looking at the sectional charts. That's basically what this question is all about, among other things. $\endgroup$ – quiet flyer May 7 at 19:59
  • $\begingroup$ I see what you mean...I've worked with the FAA to change a Class E Surface airspace, and wouldn't be surprised if there was simply an error here. They juggle a lot of space. $\endgroup$ – MikeY May 7 at 20:02
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    $\begingroup$ I'd give one of their airspace guys a call and ask. $\endgroup$ – MikeY May 7 at 20:04
  • $\begingroup$ You mean an error on the interactive map ? Maybe but the thing is the interactive map exactly matches the FAA's "Airspace Designations and Reporting Points" document Order 7400.11C which is the gold standard. The depiction on the sectional charts is the red herring here it seems. $\endgroup$ – quiet flyer May 7 at 20:06

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