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This question pertains to the airspace of the USA.

The dashed magenta shape on the sectional chart around KGUP depicts the horizontal extent of the Class-E-to-surface at KGUP. Inside this perimeter, Class E airspace extends all the way down to the surface to protect the instrument approach and departure routes at KGUP by imposing stricter visibility and cloud clearance requirements than would exist in Class G airspace. In the FAA’s “Airspace Designations and Reporting Points” document (current edition FAA Order JO 7400.11D), this airspace is listed as “E2” airspace. (See page E-116). A characteristic of E2 airspace is that it completely surrounds and includes the airport whose approaches it is designated to protect.

The dashed magenta shapes on the sectional chart near KMFR depict the horizontal extent of the Class-E-to-surface “extensions” at KMFR. Inside this perimeter, Class E airspace extends all the way down to the surface to protect the instrument approach and departure routes at KMFR by imposing stricter visibility and cloud clearance requirements than would exist in Class G airspace. In the FAA’s “Airspace Designations and Reporting Points” document (current edition FAA Order JO 7400.11D), this airspace is listed as “E4” airspace. (See page E-186). A characteristic of E4 airspace is that it does not actually include the airport whose approaches it is designated to protect.

The fundamental reason that E4 "extensions" exist at all, rather than simply being part of the adjoined Class D airspace, is to avoid to imposing a radio communications requirement on VFR pilots passing through this airspace, which may be rather distant from the airport itself, in VMC conditions. (Note how far the E4 "extensions" extend beyond the Class D circle at KMFR.) Since E2 and E4 airspace both offer down-to-ground-level protection for instrument approaches, it seems illogical that they should be treated substantially differently by the FARs, apart from the requirement for the establishment of radio communications by VFR conditions in VMC conditions.

Yet many FARs are worded in a way that does seem to leave open the possibility that they are not meant not apply to the E4 "extension" airspace, i.e. that substantially stricter conditions are imposed in E2 airspace than in E4 airspace. (And conversely, in the case of FAR 91.157(a), the possibility seems to be left open that a privilege-- the privilege to operate under "Special VFR"-- may be granted in E2 airspace but not in E4 airspace.)

The crucial issue is whether or not phrases like "within the lateral boundaries of the surface area of Class E airspace designated for an airport", "within the lateral boundaries of controlled airspace designated to the surface for an airport", "within the airspace contained by the upward extension of the lateral boundaries of the controlled airspace designated to the surface for an airport”, and "within a Class E surface area designated for an airport" should be construed to include E4 airspace, i.e. the "extensions" like we see outside the Class D airspace at KMFR.

Here are some of the specific FARs that contain one of these phrases:

  • A) Certain FARs include the phrase “within Class A, Class B, Class C, or Class D airspace or within the lateral boundaries of the surface area of Class E airspace designated for an airport". FAR 103.17 uses this phrase to indicated the airspace where prior authorization is required to operate an ultralight aircraft.

  • B) Certain FARs and other regulations include the phrase “in Class B, Class C, or Class D airspace or within the lateral boundaries of the surface area of Class E airspace designated for an airport“. FAR 107.41 uses this phrase to indicate airspace where prior authorization is required to operate a “small unmanned aircraft”. The October 2018 44809 Exception for limited recreational operations of unmanned aircraft ("Recreational Exception") uses this phrase to indicate airspace where prior authorization is required to operate a “small unmanned aircraft”, i.e. a remote-controlled model airplane, hobby "drone", etc, under the terms of the Recreational Exception.

  • C) Certain FARs include the phrase “within the lateral boundaries of the surface areas of Class B, Class C, Class D, or Class E airspace designated for an airport”. FAR 91.155(d) uses this phrase to indicate airspace where 3 miles visibility is required to take off, land, or enter a traffic pattern under Visual Flight Rules with no special VFR clearance. FAR 91.303(c) uses this phase to indicate airspace where aerobatic flight is prohibited. FAR 91.309(a)(4) uses this phrase to indicate airspace where a pilot must notify the control tower, or the appropriate the Flight Service Station, before conducting glider towing operations. FAR 101.33(a) uses this phrase to indicate airspace where prior authorization is required for operation of unmanned free balloons, if those operations are conducted below 2000’ AGL. FAR 135.205(b) uses this phrase to indicate airspace where a ½-mile daytime, 1-mile nighttime visibility requirement applies to part-135 helicopter operations.

  • D) Certain FARs include the phrase “within the lateral boundaries of controlled airspace designated to the surface for an airport”. FAR 91.155(c) uses this phrase to describe the airspace where a Special VFR clearance is required to operate under Visual Flight Rules below a 1000’ AGL ceiling.

  • E) Certain FARs include the phrase “within the airspace contained by the upward extension of the lateral boundaries of the controlled airspace designated to the surface for an airport”. FAR 91.157(a) uses this phrase to indicate the airspace where operations under 10,000’ MSL may be conducted under the relaxed cloud clearance and visibility requirements afforded by a special VFR clearance.

  • F) Certain FARs include the phrase “within the lateral boundaries of the surface areas of Class B, Class C, Class D, or Class E airspace designated for the takeoff airport”. FAR 45.22(a)(3)(ii) uses this phrase to indicate airspace where prior approval of the responsible Flight Standards Office is required to operate an aircraft bearing non-standard markings for exhibition purposes.

  • G) Certain FARs include the phrase “within Class B, Class C, or Class D airspace, or within a Class E surface area designated for an airport in which flights are intended”. FAR 121.347(a)(2) uses this phrase to indicate airspace in which aircraft operating under part 121 under VFR along routes that can be navigated pilotage must be equipped with the radio equipment necessary to communicate with appropriate ATC facilities.

  • (Note that FAR 137.43(b) has a significantly different construction than the other FARs listed above. It uses the phrase “within the lateral boundaries of a Class E airspace area that extends upward from the surface” to describe the airspace where a person may not conduct agricultural aircraft operations under weather conditions below VFR minimums without prior authorization. There seems to be no ambiguity here. Perhaps there is a specific reason why the other FARs listed above didn’t use the same construction, and included the “designated for an airport” phrase?)

The common thread in all these FARs (except for FAR 137.43(b)) is the phrase “surface area of Class E airspace designated for an airport”, or the phrase “controlled airspace designated to the surface for an airport”, or another similar phrase including the words "designated for an airport" or "designated...for an airport."

The question(s): What (if any) specific indications have the FAA given that this phrasing should be construed to include E4 Class-E-to-surface “extensions” such as those at KMFR? And what (if any) specific indications have the FAA given that this phrasing should not be construed to include E4 Class-E-to-surface “extensions” such as those at KMFR? And which is the better interpretation of the language of the Federal Aviation Regulations, including the “Airspace Designations and Reporting Points” document, FAA Order 7400.11D?

A couple of additional points may further inform the question:

  1. Here's the primary argument that phrases like "surface area of Class E airspace designated for an airport" should not be construed to include E4 airspace, i.e. the "extensions":
  • FAR 71.1 establishes that the FAA’s “Airspace Designations and Reporting Points” document, current edition FAA Order JO 7400.11D, is incorporated by reference into the Federal Register, and thus legally constitutes part of the Federal Aviation Regulations, and provides “a listing for Class A, B, C, D, and E airspace areas”. The Airspace Designations and Reporting Points document (current edition FAA Order JO 7400.11D) uses the following phrases to name or describe E2 airspace: “6002. Class E Airspace Areas Designated as a Surface Area” (page vii), and “6002. Class E Airspace Areas Designated as Surface Areas. The Class E airspace areas listed below are designated as a surface area for an airport.” (page E-1). The same document uses the following, significantly different phrases to name or describe E4 airspace: “6004. Class E Airspace Areas Designated as an Extension to a Class D or Class E Surface Area” (page x), and “6004. Class E Airspace Areas Designated as an Extension to a Class D or Class E Surface Area. The Class E airspace areas listed below consist of airspace extending upward from the surface designated as an extension to a Class D or Class E surface area.” (page E-155). Should these names and descriptions be considered to be merely supplemental, explanatory content, or do they legally designate E2 airspace as the only subclass of Class E airspace that should be considered to be “designated as a surface area”, and likewise as the only subclass of Class E airspace that should be considered to be "designated for an airport"? It certainly seems that the authors of the "Airspace Designations and Reporting Points" document went out of their way to avoid applying these phrases to E4 airspace, and to reserve them for E2 airspace.
  1. And here's an argument in support of the idea that phrases like "surface area of Class E airspace designated for an airport" should be construed to include E4 airspace, i.e. the "extensions":
  • FAR 71.71 lists and describes all Class E airspace. This is done in large part by reference to the "Airspace Designations and Reporting Points" document (current edition FAA Order JO 7400.11D). Far 71.71 states: “Class E airspace consists of (a)…, (b) The airspace areas designated for an airport in subpart E of FAA Order 7400.11D (incorporated by reference, see § 71.1) within which all aircraft operators are subject to the operating rules specified in part 91 of this chapter, (c)…, (d)…, (e)…, (f)….” E4 airspace cannot possibly be described by (a), (c), (d), (e), or (f), because these clauses all describe Class E airspace that does not extend all the way to the surface. So unless we take the absurd position that E4 airspace is actually not Class E airspace it all, it seems that we are forced to conclude that FAR 71.71 does in fact consider E4 airspace to be “designated for an airport in subpart E of FAA Order 7400.11D”, notwithstanding the titles and descriptions actually used in FAA Order 7400.11D.

What specific guidance has the FAA given on how to resolve the apparent discrepancy between the language of FAR 71.71 and the language of the "Airspace Designations and Reporting Points" document, FAA Order 7400.11D? In the eyes of the FAA, do phrases like "surface area of Class E airspace designated for an airport" apply to the E4 "extensions", or not?

Please note that this question is only intended to be about the horizontal extent of the airspace that should be considered to encompassed by the meaning of “within the “surface area of Class E airspace designated for an airport”, and other similar phrases — not the vertical extent of this airspace.

Related ASE questions--

Does FAR 91.155c apply to class E surface extensions?

Does an SVFR clearance extend to Echo surface extensions?

Which parts of class E airspace can an ultralight (part 103) fly in without prior ATC authorization?

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  • $\begingroup$ Similar questions have been asked before but never in a way that tied together all of the different FARs affected by this question. $\endgroup$ – quiet flyer Feb 20 at 17:34
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    $\begingroup$ just an observation and friendly opinion - you obviously have a great deal of knowledge and interest in the subtleties of the various sub-categories of class E airspace, (which I didn't even know existed before you pointed them out in your earlier questions!) but this is in danger of being labeled TLDR. (too long, didn't read) I get that this is probably more important for ultralight pilots and I hope you get the answers you are seeking, but I am struggling to find the relevancy. There is a lot of information in your question to sift through, and frankly I gave up trying... $\endgroup$ – Michael Hall Feb 20 at 17:53
  • $\begingroup$ Make it relevant then. I have been flying for 37 years and never once have I wondered whether I was in E2 or E4 airspace, or considered what I might need to do differently as a result. $\endgroup$ – Michael Hall Feb 20 at 20:50
  • $\begingroup$ SVFR might be relevant $\endgroup$ – quiet flyer Feb 20 at 20:53
  • $\begingroup$ Not to me it isn't. If I need to I will go IFR. $\endgroup$ – Michael Hall Feb 20 at 20:54
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Here are some indications that the FAA has given that phrases like "surface area of Class E airspace designated for an airport" do include E4 Class-E-to-surface "extensions":

  1. In the current Aeronautical Information (AIM), section 3-2-6(e)(2) contains the following sentence (italics and bolding added):

Surface area arrival extensions become part of the surface area and are in effect during the same times as the surface area.

The above sentence first appeared in the AIM in the 2016 edition, and appears to reflect no specific change in the relevant FARs or the "Airspace Designations and Reporting Point" document.

  1. In relation to item "E" in the present question, and also in relation to FAR 91.157(a) -- consider a case where E4 airspace adjoins Class D airspace with a part-time tower, and the Class D airspace (but not the E4 airspace) is specified in the Airspace Designations and Reporting Points document (FAA Order JO 7400.11D) to convert to E2 airspace during the hours that the tower is closed. (This is quite common, but see this ASE question for an alternative arrangement.) When queried by telephone about such a case, many Air Traffic Control Center personnel said during the hours the tower was closed and the E2 airspace was controlled by the Air Traffic Control Center, they would have no problem issuing a Special VFR Clearance throughout the entire “Echo Surface Area”, by which they meant all the Class-E-to-surface airspace including the E4 “extensions”. (However, some other Air Traffic Control personnel said that E4 “extensions” would generally not be included in a Special VFR Clearance in such a case, but due to operational considerations rather than a lack of regulatory authority to include them. For more details, see this related ASE question.)

And here are some indications that the FAA has given that phrases like "surface area of Class E airspace designated for an airport" do not include E4 Class-E-to-surface "extensions":

  1. In relation to item "E" in the present question, and FAR 91.157(a) -- a related ASE answer provided a (circa) 2010 response from the FAA ATO Western Service Center addressing the question of whether "Special VFR" operations may be conducted in E4 Class-E-to-surface "extensions". Although the specific example in question was complicated by the fact that the airport's Class D airspace was specified to revert to Class G airspace rather than to E2 Class-E-to-surface airspace when the tower closed for the night, and thus the local ATC Center was not to used to routinely handling requests for Special VFR Clearances for any of the airspace associated with that airport, the FAA ATO Western Service Center's response nonetheless did contain the following passage:

Our opinion is that E4 airspace is not part of the airspace designated as the surface area for an airport. The surface area for an airport is D, C, or E2. Extensions are treated differently from surface areas designated for an airport, ie there is no communication requirement. In addition extensions, by definition in 7400.9, are not airspace designated as the "surface area for an airport".

  1. As noted in item "B" in the present question, FAR 107.41 states “No person may operate a small unmanned aircraft in Class B, Class C, or Class D airspace or within the lateral boundaries of the surface area of Class E airspace designated for an airport unless that person has prior authorization from Air Traffic Control (ATC)”. A memorandum issued on January 8, 2018 by FAA staffer Scott J. Gardner, Acting Manager, Emerging Technologies, AJV-115, stated that according to the FAA's Airspace Designations and Reporting Points document, "The only type of Class E airspace that matches the language in 107.41" is E2 airspace. The memorandum stated:

In reviewing Class E Surface Area authorization requirements, we determined that the Class E authorization requirement only pertains to Class E surface areas for an airport, not the Class E extensions to Class D, C and E airspaces.

  1. In keeping with item (2) immediately above, the FAA's LAANC system for authorizing flight of Small Unmanned Aircraft under FAR 107 (and also under the October 2018 44809 Recreational Exception for limited (hobby) recreational operations of unmanned aircraft, which uses the same phrasing as FAR 107.41)) does not include any E4 Class-E-to-surface "extension" airspace in the "gridded" airspace where authorization may be requested, thus implying that no authorization is required to operate a Small Unmanned Aircraft System (sUAS) or hobby model airplane, drone, etc in this airspace under the terms of FAR 107 or the October 2018 Recreational Exception.

  2. In keeping with items (2) and (3) immediately above, this 2019 Power Point document entitled "Class E airspace", compiled by FAA Aviation Safety Inspector Kevin Morris for an FAA UAS (Unmanned Aircraft System) Symposium, contains graphics clearly indicating that no authorization is needed to operate an "unmanned aircraft" in E4 airspace-- i.e. in the "extensions" to Class D or E2 airspace-- despite the language of FAR 107.41. Note specifically the inclusion of KTVL (Lake Tahoe airport) as one of the illustrated examples.

  3. If there were no operational difference between E2 airspace surrounding an airport and E4 "extensions", it is difficult to imagine why the FAA would ever designate an E4 "extension" to full-time E2 airspace, as has been done at Lake Tahoe Airport (KTVL) and Humboldt Country Airport (KACV), rather than simply making the entire area one unified piece of E2 airspace.

The present question goes on to ask:

And which is the better interpretation of the language of the Federal Aviation Regulations, including the “Airspace Designations and Reporting Points” document, FAA Order 7400.11D?

It seems clear that the argument "2" in the present question, based on FAR 71.71 and supporting the idea that phrases like "surface area of Class E airspace designated for an airport" do include E4 Class-E-to-surface "extensions", is stronger than argument "1" in the present question, based on the "Airspace Designations and Reporting Points" document (FAA Order 7400.11D) and supporting the opposite view. Of course, even if the only practical effect of an E4 "extension" were to impose, all the way to ground level, stronger cloud clearance and visibility requirements than the standard Class G requirements, this would still provide some added protection to IFR approach and departure paths. But it's difficult to imagine that the FAA ever intended that regulations such as FAR 101.33(a), which requires prior authorization for the operation of unmanned free balloons below 2000' AGL, should not apply in the E4 "extensions" that protect the approach and departure paths.

Before the 1993 airspace re-organization that gave us the current "alphabet" classes, all of the FARs listed in the present question (except those not yet in existence) simply referred to "control zones" rather than using phrases like "surface area of Class E airspace designated for an airport". Since at that time, communications requirements were not contingent upon whether or not a given airspace was within a "control zone", there was no need for the control zones to have "extensions". The "control zones" were simply sized and shaped as needed to include all the airspace where it was desired that enhanced cloud clearance and visibility requirements be extended all the way to ground level. The FARs were written such that the same boundaries were also used in relation to SVFR authorization, the prohibition of aerobatics, the requirement for special authorization for ultralight flight or unmanned free balloon flight, etc, as per the various FARs listed in the present question. However, at the time of the 1993 "alphabet" airspace re-organization, the regulations had to be converted into new phraseology, since "control zones" no longer existed. Arguably, at this point in time there was a failure to adopt clear and consistent language that would have allowed the newly modified versions of the FARs to mesh easily with the new "Airspace Designations and Reporting Points" document, and ever since then, confusion has existed within the FAA as well as within the pilot community as to whether or not the dozen or so FARs listed in the present question do or do not apply to E4 "extensions". (Read more about this history in this related ASE answer.)

Here is one of the more astounding results of the ongoing confusion and ambiguity around this issue. It seems obvious that when the October 2018 44809 Exception for limited recreational operations of unmanned aircraft ("Recreational Exception") was created-- undoubtedly with substantial FAA input-- the authors assumed that by including the phrase "within the lateral boundaries of the surface area of Class E airspace designated for an airport" within the list of places where prior authorization was required, E4 airspace would become off-limits for recreational model aircraft, or accessible only under strict conditions, including an altitude limit prescribed at the time the authorization was issued. The legislation contains no other provision for limiting the altitude to which model airplanes, hobbyist drones, etc may be flown in E4 airspace. Therefore the FAA's assertion that E4 airspace does not fall within the meaning of "within the lateral boundaries of the surface area of Class E airspace designated for an airport" has the bizarre consequence of setting aside E4 airspace-- the airspace protecting instrument approach and departure paths-- as the only airspace in which model airplanes, hobbyist drones, etc may be flown with no altitude restriction whatsoever.1 This is not the case for part 107 operations, because part 107 contains a blanket 400' height limit, with certain well-prescribed exceptions.

Footnotes--

  1. Actually, the plot is even more twisted than that-- the case may be made that after using the E4 airspace as an "elevator shaft" to ascend from ground level to the floor of the overlying sheet of Class E airspace (typically at 700' AGL or 1200' AGL), a model airplane or hobbyist drone pilot operating under the Recreational Exception may then freely roam around the Class E airspace at any altitude above the Class E floor, without being confined to stay within the footprint of the E4 extension. The key point being that unlike the situation with Part 107, the 400' altitude limit in the Recreational Exception only applies in uncontrolled airspace.
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  • $\begingroup$ This answer would benefit from the inclusion of content related to the following: regarding the issue of the apparent lack of any altitude limit, as well as any apparent requirement for "prior authorization", for rc hobbyists' model airplanes, "drones", etc in E4 airspace (the "extensions") -- one FAA staffer attempted to resolve this issue by way of the following response -- rcgroups.com/forums/showpost.php?p=43098213&postcount=11 . (ctd...) $\endgroup$ – quiet flyer 2 days ago
  • $\begingroup$ (ctd) Note that the staffer does not argue that any prior authorization is required for operations under 14 CFR 44809 in E4 airspace. In fact, the staffer specifically writes "or surface E airspace designated for an airport (E2)", essentially acknowledging that "surface E airspace 'designated for an airport'" can be reasonably construed not to include E4 airspace, which means that no prior authorization is required for hobbyist model airplane/ drone/ etc operations in E4 airspace under either 14 CFR 4480 (the "Recreational Exception") or Part 107 . (ctd...) – $\endgroup$ – quiet flyer yesterday
  • $\begingroup$ (ctd) The rest of the staffer's response is basically non-logical-- in essence he seems to be saying "we forgot to adequately spell out what restrictions we'll impose on you if you engage in this particular activity (flight in E4 airspace) which would otherwise be allowed under 14 CFR 44809 (the "Recreational Exception"), and this oversight leads to bizarre results, so therefore you are not permitted to engage in this particular activity under 14 CFR 44809, so you are controlled by Part 107 whenever you are in E4 airspace. And Part 107 imposes a blanket 400' altitude ceiling, apart from (ctd) $\endgroup$ – quiet flyer yesterday
  • $\begingroup$ (ctd) And Part 107 imposes a blanket 400' altitude ceiling, apart from some specific exceptions." That simply doesn't compute. Just because the FAA failed to set an altitude limit for hobbyist model airplane / drone flight in a certain airspace (E4 airspace) under the terms of the "Recreational Exception", doesn't logically imply that flight in that airspace may not be conducted under the "Recreational Exception". Only if one takes it as a "given" that the regulations contain no oversights and never produce illogical results, could that sort of argument "hold water". $\endgroup$ – quiet flyer yesterday
  • $\begingroup$ This answer would benefit from the inclusion of content relating to the following-- there are instances where the FAA uses the phrase "Surface Area", even without the additional phrase "... designated for an airport", to signal that E2 airspace is being referenced and E4 airspace is not being referenced. Examples: NPRM on airspace expansion... $\endgroup$ – quiet flyer yesterday

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