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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?

quiet flyer
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  • Possible duplicate of Can the Class-E-to-surface airspace at Eagle County Regional airport KEGE be ignored when the tower is open? – Juan Jimenez May 07 '19 at 15:32
  • Dashed Class E is about protecting approaches. – Juan Jimenez May 07 '19 at 15:34
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    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 – quiet flyer May 07 '19 at 18:57
  • Class E is not about tower/no-tower. KEGE has a precision approach and that is what the Class E protects. – Juan Jimenez May 08 '19 at 08:15
  • Again, no relation to tower or tower service, just approaches. – Juan Jimenez May 08 '19 at 14:50
  • The point that I am trying to make is that since Class E's respond to approach configurations and other issues, there is no reason to expect rhyme nor reason in what they look like, etc. That is why there is no "unusual" configuration for these. They respond to the circumstances of what the FAA wants to achieve at that particular location. What the chart is depicting says that the airports do not have the same airspace configuration. – Juan Jimenez May 09 '19 at 08:31
  • This question is now answered here https://aviation.stackexchange.com/a/84358/34686 . Actually, I forgot the present question existed, when I added the "bonus question" part to the other related question. – quiet flyer Feb 17 '21 at 19:31
  • Perhaps I ought to delete the present question? – quiet flyer Feb 17 '21 at 19:31
  • Except that someone else has offered an answer, so... ? – quiet flyer Feb 17 '21 at 19:32
  • Or I could edit https://aviation.stackexchange.com/questions/63970/what-is-the-primary-reason-that-the-non-towered-airports-acv-tvl-sgu-bih-and to remove the part that duplicates this question-- – quiet flyer Feb 17 '21 at 19:54
  • But I really think https://aviation.stackexchange.com/questions/63970/what-is-the-primary-reason-that-the-non-towered-airports-acv-tvl-sgu-bih-and is a better question with the new addition. Guess I won't do anything for right now, until someone insists. – quiet flyer Feb 17 '21 at 20:52
  • PS the airspace at KTPL has now been reconfigured to a smaller size, and there is no longer any E4 "extension" airspace there. – quiet flyer Feb 17 '21 at 22:13
  • More recent changes-- the airspace at KTLV has been reconfigured to drop the extension-- see http://vfrmap.com/?type=vfrc&lat=38.894&lon=-119.995&zoom=10&api_key=763xxE1MJHyhr48DlAP2qQ. Also, the chart illustration at KACV has been changed to drop the segmented line between the core E2 circle and the E4 "extension"--see http://vfrmap.com/?type=vfrc&lat=40.978&lon=-124.108&zoom=10&api_key=763xxE1MJHyhr48DlAP2qQ -- it seems the FAA has now standardized on this method of depicting E4 "extensions" to E2 airspace in cases where no Class D (or higher) airspace is involved. – quiet flyer Jan 05 '22 at 18:31

2 Answers2

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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.

quiet flyer
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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...

MikeY
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  • 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) – quiet flyer May 07 '19 at 19:57
  • (Continuing) If you go look at the FAA interactive sUAS map ( https://faa.maps.arcgis.com/apps/webappviewer/index.html?id=9c2e4406710048e19806ebf6a06754ad ) 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. – quiet flyer May 07 '19 at 19:59
  • 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. – MikeY May 07 '19 at 20:02
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    I'd give one of their airspace guys a call and ask. – MikeY May 07 '19 at 20:04
  • 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. – quiet flyer May 07 '19 at 20:06
  • I agree the sectional looks out of sync. An interesting question, since the FAA stuff is the law, is which takes precedence when a conflict arises? Chart or airspace docs? – MikeY May 07 '19 at 20:13
  • Not the chart! The documents – quiet flyer May 07 '19 at 20:13
  • Curious what airspace designation you were able to get changed. If you care to chat a bit more I'll send you a message from a room I just created. – quiet flyer May 07 '19 at 20:18
  • Let us continue this discussion in chat. – MikeY May 07 '19 at 20:20
  • MikeY, do you possibly want to consider deleting your answer to this question? You could save to clipboard and then repost to the other related question, if you wished. The reason I'm asking is that I'd really prefer to delete this question since I've forgetfully gone and essentially added it to the related question https://aviation.stackexchange.com/questions/63970/what-is-the-primary-reason-that-the-non-towered-airports-acv-tvl-sgu-bih-and , but I don't want to delete a question with someone else's answer attached. It's up to you, no problem either way. If you are still visiting ASE... – quiet flyer Feb 17 '21 at 21:29