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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 the airport whose approaches it is designated to protect. On page E-1 of the "Airspace Designations and Reporting Points" document, in the header for the section listing all the E2 airspace areas, we read "The Class E airspace areas listed below are designated as a surface area for an airport."

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. On page E-155 of the "Airspace Designations and Reporting Points" document, in the header for the section listing all the E4 airspace areas, we read "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." Nowhere in the header for the E4 section do we find the phrases "designated for an airport" or "designated as a surface area for an airport".

The fundamental reason that this E4 airspace at KMFR was designated as E4 airspace rather than as part of the Class D airspace at KMFR, is to avoid to imposing a radio communications requirement on VFR pilots passing through this airspace in VMC conditions.

  • 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” under the terms of the 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.

The common thread in all these FARs 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 has 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 has 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?

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.

The answers to these questions should ideally include references to specific FAA memoranda, letters of clarification and interpretation, other relevant documents, etc.

Here is a little more additional background information that may help to better inform these question(s)—

  1. 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?

  2. 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 to convert to E2 airspace during the hours that the tower is closed. 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”. But other Air Traffic Control personnel said that the E4 “extensions” would never be included in a Special VFR Clearance in such a case. Answers seemed to vary from region to region.

  3. 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 for an airport”, and likewise as the only subclass of Class E airspace that should be considered to be "designated for an airport"?

  4. 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. Does this mean that E4 airspace is actually not Class E airspace at all? (Surely not.) Or does this mean that E4 airspace should in fact considered 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? Or does this mean something else?

It seems that there is a contradiction between the language of FAR 71.71 and the language of FAA Order 7400.11D, which legally is a part of the FAR as well. The question being asked here, is essentially "what guidance has the FAA given on how to resolve this contradiction, in terms of whether or not E4 Class-E-to-surface 'extension' airspace should or should not be considered to included by phrases like 'surface area of Class E airspace designated for an airport', 'controlled airspace designated to the surface for an airport,'and the other similar phrase used in the FARs quoted above."

A reminder— items 1 through 4 are only meant to provide supplemental information to help understand the motivation behind the actual question(s). The actual point of the question(s) is to ask for specific FAA memorandum, letters of interpretation, documents, etc. stating that E4 “extensions” should or should not be considered to fall within the airspace described by the phrase “within the lateral boundaries of the surface area of Class E airspace designated for an airport” and the other similar phrases used in the various FARs listed above, and also to ask whether or not the interpretation given in these memorandum, letters of interpretation, etc. really seems to be the best possible interpretation of the (apparently somewhat inconsistent) language of the Federal Aviation Regulations, including FAA Order JO 7400.11D.

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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.

This 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. As noted in supplementary item 2 in the question, when queried by telephone, many air traffic controllers stated that they were willing to authorize "Special VFR" flight in E4 Class-E-to-surface "extensions". Many air traffic controllers refer to all Class-E-to-surface airspace as a "Class Echo Surface Area", without regard to whether that airspace is E2 airspace or E4 airspace, and state that they do have the authority to issue a "Special VFR" clearance that is valid throughout a given "Class Echo Surface Area". This includes cases where an E4 Class-E-to-surface "extension" adjoins an E2 Class-E-to-Surface central core area -- a situation that most commonly arises when a part-time control tower closes for the night and the Class D airspace associated with that control tower reverts to E2 Class-E-to-surface airspace.

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. A related ASE answer provided a 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. 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 recreational operations of unmanned aircraft) 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) in this airspace under the terms of FAR 107 or the October 2018 Recreational Exception.

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  • $\begingroup$ (future edit--"(and also under the October 2018 44809 Recreational Exception for limited recreational operations of unmanned aircraft) which includes identical language)" $\endgroup$ – quiet flyer Mar 17 at 17:47

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