Can an ultralight fly within the two Class E extensions to the Class D airport?
Or are these two extensions still considered "surface areas of Class E airspace designated for an airport"
Re the phrase "within the lateral boundaries of the surface area of Class E airspace designated for an airport"--
This phraseology appears in FAR 103.17 (applies to ultralight aircraft), FAR 107.41 (applies to small unmanned aircraft systems, i.e. "drones"), and now also in the newly passed HR 302 which includes regulation of small unmanned aircraft systems which apparently now include all hobbyist radio-control aircraft.
This FAA Memorandum from January 10, 2018 makes it clear that the phrase "within the lateral boundaries of the surface area of Class E airspace designated for an airport" does NOT include the airspace above the ground surface within dashed magenta "extensions" that do NOT actually surround the airport whose approaches they protect-- like this -- .
On the other hand, the airspace above the ground surface within the dashed magenta line on this picture is an example of airspace that IS "within the lateral boundaries of the surface area of Class E airspace designated for an airport".
Here is a video from a school for commercial drone pilots that describes the distinction in plain language for the benefit of students.
The January 10 2018 Memorandum relies heavily on the specific language in FAA Order 7400.11B, "Airspace Designations And Reporting Points", which is the document that legally defines all the different airspace structures that make up the nation's airspace, and precisely delineates their boundaries. The key point is that at the beginning of the part of that document that describes the Class-E-to-surface airspaces that actually surround the airports whose approaches they protect, we find the heading "Class E Airspace Areas Designated as a Surface Area", followed by the descriptive sentence "The Class E airspace areas listed below are designated as a surface area for an airport." We don't find the same language at the beginning of the part of the document that describes the "extensions".
The January 10 2018 Memorandum is in relation to unmanned autonomous vehicles, but since FAR 103.17 uses the identical phraseology, ("within the lateral boundaries of the surface area of Class E airspace designated for an airport"), the only logical conclusion is that ultralight aircraft CAN fly over those dashed magenta Class-E-to-surface "extension" areas with no special permission.
If there are past FAA rulings/ interpretations that contradict the January 10 2018 Memorandum referenced above, or contradict the implications in relation to ultralight aircraft that I've drawn from the January 10 2018 ruling, and which would therefore suggests or rule that ultralight aircraft are NOT allowed to fly over Class-E-to-surface "extensions" that do not actually envelope the relevant airport without special permission -- please add links to those documents to this post.
The precise meaning of the phrase "within the lateral boundaries of the surface area of Class E airspace designated for an airport" also bears on where we may operate under "Special VFR", and where we must have a "Special VFR" clearance if the ceiling is below 1000' AGL. See this answer to the question "Does FAR 91.155c apply to class E surface extensions?" for more.
It is possible that we will see some FAA rulings that impact on these topics in the near future. As things stand right now, there appears to be a loophole in regulations that will go into effect in the near future (HR 302) regarding Small Unmanned Aircraft (radio-controlled airplanes and "drones"), which will allow SUA's to operate above 400' altitude without "prior authorization from Air Traffic Control" ONLY if they are in Class-E-to-surface "extensions", and nowhere else in the nation's airspace-- except perhaps in Class E not-to-surface airspace that was entered from a Class-E-to-surface "extension", or after climbing above the top of the Class E floor while flying "with prior authorization" in Class B, C, or D airspace or while flying with "prior authorization" in Class-E-to-surface airspace of the "designated for an airport" variety. It is unlikely that this is what was intended. There are at least two logical ways to fix the problem: 1) extend the 400' AGL limit (in the absence of "prior authorization") to all airspace, not just Class G, or 2) explicitly include all Class-E-to-surface airspace including "extensions" in the airspace in which "prior authorization" is needed. However, it is possible that the FAA will simply bludgeon the issue into submission and overrule the January 10 2018 memorandum, however well-founded it may be, by ruling that the meaning of "within the lateral boundaries of the surface area of Class E airspace designated for an airport" DOES include the Class-E-to-surface extensions.
Now read on for much more--
How to better understand the rationale behind the January 10 2018 Memorandum?
The January 10 2018 document explicitly cited the FAA's "Airspace Designations And Reporting Points", JO 7400.11B . (Replaced in August 2018 by Order JO 7400.11C, which has no changes of significance to this question. Page references in this answer are to the August 2018 edition.) This document clearly divides Class-E-to-surface airspace into two different types--
One type is identified on page vii: "Class E Airspace Areas Designated as a Surface Area" . On page E-1 this heading is repeated, followed by the descriptive sentence "The Class E airspace areas listed below are designated as a surface area for an airport". When one reads the actual individual airspace descriptions, it is clear that each of these particular Class-E-to-surface airspace areas actually surrounds the airport whose approaches it protects.
The other type is identified on page ix -- "Class E Airspace Areas Designated as an Extension to a Class C Surface Area" and on page x -- "Class E Airspace Areas Designated as an Extension to a Class D or Class E Surface Area". On page E-141 we find the shorter heading "Class E Airspace Areas Designated as an Extension", followed by the descriptive sentence "The Class E airspace areas listed below consist of airspace extending upward from the surface designated as an extension to a Class C surface area." Similar language is repeated on page E-156 in regard to extensions to Class E airspace areas. When one reads the actual individual airspace descriptions, it is clear that none of these Class-E-to-surface airspace areas actually surrounds the airport whose approaches it protects. Nowhere in these parts of JO 7400 do we find the phrase "designated for an airport".
And what is the precise language of FAR 103.17?
"No person may operate an ultralight vehicle 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 unless that person has prior authorization from the ATC facility having jurisdiction over that airspace."
The casual reader of FAR 103.17 and FAR 107.41 might wonder whether the phrase "designated for an airport" really has any significance. Is this phrase really meant to distinguish the type of class-E-to-surface airspace that surrounds an airport whose instrument approaches it protects, from the type that is merely an "extension" that abuts up against the airspace of the airport whose instrument approaches it protects?
In the light of the precise language of Order JO 7400 as noted above, the answer has to be an unambiguous "yes"-- and that is exactly what the FAA found in the January 10 2018 Memorandum.
The phrase "surface area" in FAR 103.17 and FAR 107.41 could be said to be a "loaded" phrase as well. Does this mean "designated as a Surface Area", as used in FAA Order JO 7400 for the title of the section that describes the type of Class-E-to-surface airspace that actually surrounds the airspace whose approaches it protects? Or are we just noting that the bottom of the airspace happens to be in contact in the ground? Regardless of which interpretation we choose, the inclusion of the phrase "designated for an airport" is enough to leave no doubt as to which type of Class-E-to-surface airspace FAR 103.17 and FAR 107.41 are referring to.
It's also worth taking a look at the AIM (Aeronautical Information Manual).
The AIM uses the phrases "designated for an airport", "surface area", and "surface area designated for an airport" ONLY in relation to the type of Class-E-to-surface airspace that surrounds the airport whose instrument approaches it protects, and NOT in relation to Class-E-to-surface "extensions".
e. Functions of Class E Airspace. Class E airspace may be designated for the following purposes:
- Surface area designated for an airport where a control tower is not in operation. Class E surface areas extend upward from the surface to a designated altitude, or to the adjacent or overlying
controlled airspace. The airspace will be configured to contain all instrument procedures.
(a) To qualify for a Class E surface area, the airport must have weather observation...
(b) A Class E surface area may also be designated to accommodate part-time operations at a Class C or Class D airspace location (for example, those periods when the control tower is not in operation).
Extension to a surface area. Class E airspace may be designated as extensions to Class B, Class C, Class D, and Class E surface areas. Class E airspace extensions begin at the surface and extend up to the overlying controlled airspace. The extensions provide controlled airspace to contain standard instrument approach procedures without imposing a communications requirement on pilots operating under VFR. Surface area arrival extensions become part of the surface area and are in effect during the same times as the surface area.
That very last sentence does seem to create some ambiguity. Bear in mind that the AIM is not a legal document in the sense that the FAR/CFR is. Stating that the surface arrival extensions "become part of the surface area" does not necessarily mean that all regulations applying to the "Surface area designated for an airport" also apply to the Class-E-to-surface airspaces "designated as extensions to Class B, Class C, Class D, and Class E surface areas". Certainly the FAA didn't see it that way when issuing the January 10 2018 Memorandum.
Now let's take a look at the FAA's Pilot Controller Glossary. Does the Pilot/Controller Glossary define a "Surface Area"? Yes it does-- "SURFACE AREA- The airspace contained by the lateral boundary of the Class B, C, D, or E airspace designated for an airport that begins at the surface and extends upward." Again, this "designated for an airport" terminology is exactly the same language that we find in Order JO 7400. This further supports the idea that the FAA intends the phrase "surface area" to be used only in relation to the type of Class-E-to-surface airspace that surrounds the airspace whose approaches it protects, and not in relation to the Class-E-to-surface "extensions".
Some have suggested that the phrase "designated for an airport" in FAR 103.17 is superfluous, and is not meant to differentiate between the two different types of Class-E-to-surface airspace, because the FAA uses similar language in some cases in reference to Class B or Class C airspace. This overlooks looks the point that the FAA's "Airspace Designations And Reporting Points", Order JO 7400, specifically uses this phrase to differentiate between the two different types of Class-E-to-surface airspace, as discussed above. The phrase "designated for an airport" does not appear in that document's description of Class B or Class C airspace, so the phrase likely is indeed superfluous in reference to such airspace. Why then does the phrase appear in any FAA material describing such airspaces? It probably was put there by someone who wanted to specifically refer to the part of that airspace whose base was at ground level, and copied from other sources language referring to Class-E-to-surface airspace, without appreciating the significance of the phrase "designated for an airport" in that context.
Is there an altitude limit to the concept of "within the lateral boundaries of the surface area of Class E airspace designated for an airport"?
The FAR's clearly specify that Class E airspace continues upward until it runs into some other higher category of airspace. It seems clear enough that the concept of "within the lateral boundaries of the surface area of Class E airspace designated for an airport" has no upward limit AT ALL. Basically we are just saying that the aircraft occupies some point in the sky that is above the ground-level "footprint" that is demarcated by the dashed magenta lines on the chart.
Some pilots seem to imagine that the phrase "within the lateral boundaries of the surface area of Class E airspace designated for an airport" means the airspace within, but NOT HIGHER THAN THE TOP OF, the lowermost vertical (cylindrical) green wall on this diagram: (taken from http://footflyer.com/PPGBibleUpdates/Chapter08/AirspaceQuestion/AirspaceQuestion.htm )
I.e. the airspace that would be "held in" within the lowermost wall depicted, as if it were the wall of a moat holding in a body of water. In other words, if the innermost wall between the class E and class G airspace were somehow made visible, the pilot would only be considered to be "within the lateral boundaries of the surface area of Class E airspace designated for an airport" if he could look out horizontally while flying, and see the lower-most, innermost wall.
That interpretation is completely implausible. It is impossible to imagine that the rules for Special VFR operations-- only one aircraft allowed to be IFR or VFR within the class-E-to-surface airspace, etc-- would be confined to this area less than 700' above the ground. And are we to imagine that under the text of FAR 107.41, which contains the EXACT SAME "within the lateral boundaries of the surface area of Class E airspace designated for an airport" verbiage, that it is perfectly legal to fly a drone at 701 feet over the surface of an airport surrounded by the dashed magenta circle, with no prior authorization? Surely not.
Also, a close look at FAA order JO 7400 reveals that in cases of Class D airspace that revert to Class-E-to-surface where the tower is not open full time, we are given two different descriptions of that airspace in JO 7400. The description in the Class D section has a prescribed altitude limit (typically around 2500' AGL), while the description in the section entitled "Class E Airspace Areas Designated as a Surface Area" has no specific prescribed altitude limit.
Finally, consider this: FAR 101.33 states:
"§101.33 Operating limitations.
No person may operate an unmanned free balloon—
(a) Unless otherwise authorized by ATC, below 2,000 feet above the surface within the lateral boundaries of the surface areas of Class B, Class C, Class D, or Class E airspace designated for an airport
If the phrase meaning of the phrase "within the lateral boundaries of the surface areas of Class E airspace designated for an airport" only extended to 700' AGL, it would be perfectly legal for an unmanned balloon to be at 701' in this area with no prior authorization, despite the regulation, and there would be no reason to include any reference to Class E airspace of any kind in the regulation.
What happens when the tower closes?
It is very clear based on FAA order
JO 7400 that in most cases where the relevant control tower in class C or class D airspace is not open full time, the "surface" portion of the class C or class D airspace reverts the type of to Class-E-to-surface airspace that is called a "Class E surface area" in the AIM or a "Class E Airspace Area[s] Designated as a Surface Area for an airport" in FAA Order JO 7400. AIM 3-2-10 indicates that it is also possible for Class C or Class D airspace to revert to Class G airspace during the hours the tower is closed, but this is rare. Whenever Class D (or higher) airspace reverts to Class-E-to-surface airspace, this airspace has NO upward limit other than the floor of the next higher airspeed class above. Since ultralights are prohibited (without special permission) from flying over the type of Class-E-to-Surface airspace that is not an "extension" but rather surrounds the airport whose approaches it protects, this has the odd consequence of prohibiting an ultralight aircraft from flying (without special permission) directly above what would have been the ceiling of the Class D airspace when the tower was open, while allowing the ultralight to fly directly over that same Class D ceiling when the tower is open.
What happens when weather at the airport is above VFR minimums?
Nothing changes-- ultralights still need "prior authorization" to enter Class-E-to-surface airspace "designated for an airport", i.e. surrounding the airport whose approaches it protects. Nothing in the FAR's or AIM supports the idea that the Class-E-to-surface airspace is only "effective" during certain weather conditions, such as when the weather is so bad that VFR aircraft need an authorization for flight under Special VFR rules. This sort of terminology may be common in the ATC community, which will tend to be focussed on the need to make sure that not more than one aircraft is operating under IFR or Special VFR rules at a time within this airspace, but it is not strictly supported by anything in the FAR's or AIM. (Note: at least one FAA official at a FSDO has responded to an ultralight pilot's request for clarification on this topic by stating something to the effect that "Class-E-to-surface airspace is only active under VFR minimums. During VFR times, act as if it doesn't exist." There is other anecdotal evidence that in the past, some FSDO's have taken this approach and had no problem with ultralight operations in Class-E-to-surface airspace in good weather. This is not particularly surprising. Consistency has not been the FAA's forte on these topics, especially on the level of the FSDO's, ATC facilities, etc. Don't take this note to mean that there have not also been interpretations, possibly even official legal interpretations, to the contrary. It's pretty clear from the FAR's and the AIM what the real truth is here. )
This is the end of the main body of the answer
But read on if you want to learn how the terminology relating to Class-E-to-Surface airspace has evolved over time
To really understand how the whole concept of Class-E-to-surface airspace came about, and how this relates to the language in FAR 103.17 and 107.41, it helps to take a trip back through time.
FAR 103 was adopted July 30 1982.
Originally, FAR 103.17 said that "No person may operate an ultralight vehicle within an airport traffic area, control zone, airport radar service area, terminal control area, or positive control area unless that person has prior authorization from the air traffic control facility having jurisdiction over that airspace".
So what was a "control zone"?
"Control Zones" first appeared on charts in the mid-1940's and consisted of a thin dashed circle enclosing an airport-- originally red, later blue. By the time of this 1974 test-prep publication, control zones had been defined to go up to the overlying "Continental Control Area" at 14,500' MSL. At that time, most (but not all) towered airports had Control Zones around them, and some non-towered airports did too. By that time, special requirements in effect within a Control Zone included 3 miles visibility and a ceiling of at least 1000', unless a pilot was granted permission to fly under "special VFR" rules. Also by that time, an "Airport Traffic" area was a different thing from a "Control Zone", requiring radio communication with the tower for entry, with a smaller, standardized diameter and a much smaller, standardized vertical height. "Airport Traffic Areas" were not even depicted on sectional charts, because they were automatically present at all towered airports, and they were standardized in diameter and height. Even though Airport Traffic Areas weren't depicted on sectional charts, they were referenced on the chart legend through at least mid 1983 in the language concerning towered airports, but by sometime in late 1988 that reference had been dropped.
Bear in mind that a "control zone" is only a small subset of the larger concept of "controlled airspace". In charts dating at least back through 1969, we can see the blue shadings and magenta shadings showing whether the floor of the "controlled airspace" starts at 700' or 1200', outside of the dashed blue "control zones"-- as well as other markings to show other cases where the floor of the "controlled airspace" is at some other, higher altitude. So staying out of "control zones" has never been synonymous with staying out of all "controlled airspace"-- at least in the time period we're discussing here. From the viewpoint of a VFR pilot, entering into the most basic level of "controlled airspace" simply imposes a change in cloud clearance and visibility requirements.
Not until mid-to-late 1992 do we see dashed magenta lines (as opposed to magenta shading) appear on sectional charts. Originally, the chart legend for the dashed magenta line read as follows: "Control Zone at airport without control tower and Control Zone extension without communications requirement". The charts now contained dashed magenta lines that encircled the airports whose instrument approaches they protected-- this would be a "Control Zone at airport without control tower"-- as well as dashed magenta extensions abutting dashed blue lines encircling airports, or abutting higher classes of airspace such as TRSA's-- these would be "control zone extensions" and not actually "control zones". Presumably the "without communications requirement" applied in both cases. So now for the first time we have two different kinds of airspace enclosed by dashed magenta lines. We also still have control zones depicted by dashed blue lines-- by this time, those control zones did have a communications requirement, since one of their functions was to fill the role of the old "Airport Traffic Area". At the same time that the control zones (and control zone extensions) depicted by dashed magenta lines appeared on the chart, the charts started showing a designated, individualized ceiling for each control zone depicted by a dashed blue line, typically around 2500 AGL. This was a step toward the evolution of the current "Class D" airspace. No specific ceiling was shown on the chart for the control zones depicted by a dashed magenta line or for the control zone extensions depicted by a dashed magenta line.
FAR 103.17 never was modified to prohibit ultralights from entering "control zone extensions" without prior authorization from ATC.
In late 1993 the nation's airspace went through a substantial change in nomenclature, along with some changes in structure-- this when the current system of Classes A, B, C, D, and E came into use. By November 1993, all reference to "control zones" and "control zone extensions" vanished from the sectional charts. Now the chart legend simply said "Class D airspace" for the dashed blue lines and "Class E airspace" for the dashed magenta lines. The latter isn't terribly descriptive, given the abundance of Class E airspace-- the pilot was simply expected to understand that this was specifically a reference to the nature of the airspace right at the very surface of the earth.
Sometime around this time was when the FAA's Order 7400, "Airspace Designations And Reporting Points", was revised to delete all references to control zones. This is when we get the awkward terminology in the headings of this document. The heading of the section describing the type of Class-E-to-surface airspaces that surround the airports they protect is "Class E Airspace Areas Designated as a Surface Area". Wouldn't they have done better to title this section something like "Class-E-to-surface airspace areas designated for an airport"? The term "Surface Area" is inherently somewhat confusing, since the Class-E-to-surface "extensions" also go all the way down to the surface. As we've already noted though, the descriptive text following the titles clears things up-- the heading "Class E Airspace Areas Designated as a Surface Area" is followed by the descriptive sentence _"The Class E airspace areas listed below are designated as a surface area for an airport". We don't find this language attached to the headings for the Class-E-to-surface "extensions".
Around the same time-- specifically on September 16, 1993-- the text of FAR 103.17 was changed to include the current "No person may operate an ultralight vehicle 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 unless that person has prior authorization from the ATC facility having jurisdiction over that airspace."
Note: where italization appears in quoted material in this answer, the italization did not appear in the original source material, but rather was added to help clarify the discussion.