Let's discuss-- Part 103.17-- ultralight flight in Class-E-to-surface "extensions"

[quietflyer]

How is E4 airspace described in FAA Order JO_7400.11C? ( https://www.faa.gov/documentLibrary/...O_7400.11C.pdf )?

The specific terms used to describe E4 airspace in FAA Order JO_7400.11C include "Class E Airspace Areas Designated as an Extension to a Class D or Class E Surface Area" (page x), and "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-156)."

E3 airspace is described similarly, but as an extension to Class B or C airspace rather than to Class D or E airspace.

E3 and E4 airspace are depicted by dashed magenta lines that do NOT actually surround the airports whose approaches they protect. Examples-- E4-- the airspace in the dashed magenta shapes NNW and SSE of the Medford airport-- http://vfrmap.com/?type=vfrc&lat=42.374&lon=-122.874&zoom=10 . E3-- the airspace in the small dashed magenta shape NNE of Springfield Branson International airport-- http://vfrmap.com/?type=vfrc&lat=37....93.389&zoom=10 .

Now let's look at "E2" airspace. This is another kind of Class E airspace that goes all the way to the surface. E2 airspace is denoted by a dashed magenta line that completely surrounds the airport whose approaches it protects. Example-- The dashed magenta line around Newport Oregon denotes E2 airspace-- take a look at the sectional chart-- http://vfrmap.com/?type=vfrc&lat=44....24.058&zoom=10 .


The specific terms used to describe E2 airspace in FAA Order JO_7400.11C include "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 language is kind of clunky here-- why is E2 airspace named / described as "Designated as Surface Areas" or "designated as a surface area for an airport", while E4 airspace is not, even though both types of airspace do extend all the way to the surface, and both types of airspace clearly have something to do with a nearby airport? Well, that's bureaucracy for you.


The FAA's "Airman's Information Manual" ( https://www.faa.gov/air_traffic/publ...d_10-12-17.pdf ), while not a legal document in the sense of FAA Order JO_7400.11C, also supports this distinction in terminology. On page 3-2-9, E2 airspace is described as "Surface area designated for an airport where a control tower is not in operation", while E4 airspace is described as "Extension to a surface area" or "Class E airspace extensions". Nowhere is E4 airspace described as "Designated as a Surface Area" or "Surface Area designated for an airport" or "Surface Area", or anything similar, even though E4 airspace DOES go all the way down to the surface.


The FAA's "Pilot-Controller Glossary" ( https://www.faa.gov/air_traffic/publ...G_10-12-17.pdf ) (page PCG S-8) also supports the idea that in the context of Class E airspace, the phrase "Surface Area" should be understood to mean the type of E-to-surface airspace that is "designated for an airport". I.e. E2 airspace, not the E4 "extensions", even though both types of airspace do go all the way to the surface.


This distinction also pertains to the issue of where a clearance may be granted for Special VFR operations. FAR 91.157 only allows for Special VFR operations "below 10,000 feet MSL within the airspace contained by the upward extension of the lateral boundaries of the controlled airspace designated to the surface for an airport." There's that phrase again-- "designated to the surface for an airport". The FAA holds that the phrase "designated to the surface for an airport" applies to E2 airspace and not E4 airspace, and does not offer clearance for Special VFR operations in E4 airspace. Read more about this at these three links --

https://aviation.stackexchange.com/q...ns/55806#55806

https://aviation.stackexchange.com/q...ns/55947#55947

https://aviation.stackexchange.com/q...ns/56045#56045


The last link above in particular is highly relevant and includes a response from the FAA ATO Western Service Center stating that

"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"."

FAR 107.41 uses the phraseology "within the lateral boundaries of the surface area of Class E airspace designated for an airport" to describe where small unmanned aircraft (commercial drones) may not operate without prior authorization from ATC. The January 10 2018 FAA memorandum by Scott Gardner points out that according to the language of FAA Order JO_7400.11C, this includes E2 airspace but NOT E4 airspace. Read the memo here -- and pay special attention to the three attachments-- http://goldsealgroundschool.com/uav-...orizations.pdf -- the attachments are very enlightening.

The FAA's interactive UAS map also supports this distinction-- the E3 and E4 airspaces are clearly not included in the areas where prior authorization is required for commercial drone (UAS) flight -- https://faa.maps.arcgis.com/apps/web...06ebf6a06754ad


In short, as we look over these various documents, especially FAA Order JO_7400.11C, we are forced to the conclusion that ANY of the phrases "Surface Area" , "designated as a Surface Area", "designated for an airport", or "designated as a Surface Area for an airport", or anything similar, is sufficient to indicate that we are talking about E2 airspace (shown on chart by a dashed magenta line completely encircling the airport whose approaches it protects), not the E3 or E4 "extensions" (shown on chart by a dashed magenta line that abuts up against another dashed blue or magenta line that encircles the airport whose approaches are being protected.) Even though both the E2 and the E3 / E4 airspaces do extend all the way down to the surface.

For more, see https://aviation.stackexchange.com/q...io/55714#55714 . This answer also deals with the issue of how the present system of E2, E4, and other types of airspace, and the associated terminology, evolved over time from the mid-1940's onwards.

At the end of the day it's wise to keep in mind the following-- what is the fundamental purpose of the E3 and E4 extensions? It appears that the only purpose of the E3 and E4 extensions is to extend standard Class E cloud clearance and visibility requirements all the way to the surface, for the protection of IFR traffic emerging from clouds at low altitudes. That's all they do. You can legally fly there VFR--without speaking to anyone if you so desire-- but you can't skim the cloud-tops or cloud-bases like you can in Class G. So, there's no reason that these airspaces are fundamentally incompatible with ultralight activity, so long as it is carried out in prudent manner.

S