AIRSPACE
by Rob
McKenzie, 2018/12/3
Airspace is classified according to a
lettering system. Even though we are not allowed into Classes A, B, C, D,
Restricted or Prohibited Areas, we are allowed into nearly all of Class E and
all of Class G airspace. (as per FAR
103)
After you are done with this tutorial, a
great online source of current sectionals for anywhere in the country is
located at this site .
The Federal Aviation Administration is the
federal agency responsible to regulate aviation within the US. Most hang
gliders meet the requirements to operate as unpowered ultralight vehicles and
as such benefit from having very little in the way of regulations to follow.
Along with not needing aircraft inspections or licenses to fly them, we are
allowed to fly in most areas. Learn
more about the FAA.
Airspace
Details
Class A Airspace:
Class A airspace is not shown on your sectional. It covers the entire nation,
so all we have to remember is that its lower limit is 18,000 MSL.
The term "controlled airspace," by the way, doesn't mean that
somebody or some agency is up there controlling traffic, but controllers have
a pretty good idea of what is up there. Use of our national air traffic
control (ATC) service is mandatory in Class A airspace that begins at 18,000
feet MSL and extends upward to 60,000 feet MSL. Altitudes at 18,000 feet MSL
and above, in Class A airspace, are commonly referred to in hundreds of feet
as "Fight Levels," abbreviated FL. For example, flight level two
zero zero, or FL 200 = 20,000 feet MSL, FL 600 =
60,000 feet MSL, etc.
The United States, of course, does not own or control airspace outside its
territorial limits, but our government has extended Class A airspace out to
twelve miles from the coast of the contiguous 48 states and Alaska. By the
way, if you fly into Mexico or Canada, or if you want to rent an ultralight
overseas, do not assume that you understand their airspace system. It will be
similar, but homework is required.
Memory aid: Class A airspace = Above, as in 18,000 and Above, as in high
Above everything else.
Class
B Airspace:
Class B airspace surrounds the nation's busiest airports and usually goes as
high as 10,000 feet MSL, in some cases even higher. The uppermost level of
Class B airspace may extend horizontally with radius of up to a 15 nautical miles around the airport tower. There is,
however, no universal set of Class B dimensions since the flow of traffic,
geography and other considerations determine the exact architecture of each
Class B area. A sectional or a VFR Terminal Area Chart is very helpful in
understanding the design and lateral dimensions of each Class B airspace.
Theoretically, an ultralight might fly above Class B airspace, but that could
be extremely dangerous. Besides, you might be flying over a congested ground
area and, in certain areas, through relatively congested airspace as other
aircraft are funneled through narrow approach and departure routes.
On your sectional, horizontal Class B airspace limits are outlined in
concentric solid blue circular lines that may be indented or extended in
certain places due to geography or air traffic routes. The top and bottom of
each layer of airspace, as you can see, are given in what looks like a
fraction; for example, 90/40.
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That means that this particular layer of airspace lies
between 9,000 and 4,000 feet MSL. (SFC stands for surface) A two dimensional sectional map can only show you the
horizontal outlines of different layers, you have to use the fractions to
visualize the vertical dimensions. If it helps, close your eyes and try to
"see" the architecture of the different layers. If you try to think
in pictures rather than in words, that may help. Imagine an "inverted
wedding cake." with at least three layers.
Check your sectional and you will find that the surface area of a city lying
in Class B airspace is colored yellow as are all cities on the sectional.
Obviously, this is what the FAA would call "congested" area, and
ultralights may not fly over congested areas even if they were not in Class B
or other controlled airspace. Visual clues and good judgment are your best
guides for avoiding ground congestion.
Even though ultralights are not permitted in class B airspace without prior
permission, some operators have reported that ATC has granted permission for
individual flights. Many of the fields and airparks where ultralights fly are under overhanging layers of Class B airspace. If they
fly too high, or if they fly just above the surface toward a major city
airport, the ultralight will penetrate the Class B airspace, and that may set
off lots of alarm bells with the FAA. The inner circle of Class B airspace
extends all the way to the surface. The outskirts of cities like Portland,
Oregon and Seattle, Washington are surrounded by many delightful strips where
small planes and ultralights fly, and their pilots know pretty well what to
avoid in terms of location and altitude. Pilots who fly near major Class B
airports may prefer to use a VFR Terminal Area Chart since these depict a
smaller area with much more detail using a scale of 1:250,000. If you fly
from a field that is under or near Class B airspace, you should study your
sectional or Terminal Area Chart to memorize landmarks that might help you recognize
the locations and altitudes of various sections of Class B space.
Intruding into Class B airspace in an extremely serious matter. You may
endanger the lives of many others since a fully loaded passenger jet carries
hundreds of people. While a violation of Class D or Surface Area Class E
space (discussed below) might bring only a strong lecture, a violation of
Class B or Class C will almost certainly bring strong penalties.
In your memory, let B stand for Big Time or Big City airspace.
Class
C Airspace:
On your sectional, horizontal Class C limits are shown by solid magenta
lines. It is similar in layout to Class B but in magenta not blue.
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Altitude fractions show the upper
and lower vertical limits as they do with Class B. As with the shelves of
Class B airspace, you may fly under or over shelves of Class C airspace, but
never into the airspace itself.
If "B" stands for "Big Cities," let "C" simply
stand for Cities. The cities under class C airspace are our mid-sized cities.
The towers at these fields are equipped with radar -- something that smaller
controlled fields (Class D airspace) do not have. Ultralights may not fly in
Class C airspace without special permission from ATC, and that should be
obtained in advance by telephone (although some controllers will accept a
radio call). Although the city involved may not be as big as New York or
Washington, D.C., it will usually have heavy jet and commercial traffic
coming and going.
Class
D Airspace:
Small city airports with control towers are usually designated as Class D
airspace. Associate "D" with "Diminutive" or
"Dime-sized" cities if you like, and do not go there without
permission either. Commercial and other IFR traffic may be flying into these
fields, and there is often much general aviation activity and pilot training.
Look over your sectional and find several Class D fields. The field
silhouette itself (not the city) will be pictured in blue -- as all
controlled fields are -- with a dashed blue circle around it. By now you have
probably noticed that the runways of any airport are drawn to show their
direction in terms of the compass, and that runway length is also given.
There is more information to look for as well, but back to Class D airspace.
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The ceiling of Class D airspace
generally extends upward to 2,500 feet AGL over the airport surface but the
exact upper limit is shown with a number inside a dashed box outline. The
example at right has a "54" meaning the upper limit is 5,400' msl. Some Class D fields have little extensions, what
look like cogs on a wheel. The entire airspace may look like a key hole with
one or more extensions out from the five-mile circle. These extensions of
Class D airspace accommodate approaching and departing IFR flights that use
standard approach/departure routes.
Flying over Class D airspace may not pose problems for the experienced ultralighter unless it violates the rule that ultralights
must avoid flying over congested areas on the ground. It is customary for
general aviation traffic that is just passing over or near a Class D field,
but not planning to land there, to call the tower (the frequency is on the
sectional). Such a courtesy call lets ATC know there is traffic out there in
the general vicinity. Remember, a Class D airspace tower may have no radar
and may, except for the controllers' eyes, be blind. If you have an aircraft
frequency radio and understand radio communication procedures, it may be wise
to inform a nearby Class D tower where you are and where you plan to go.
Class
E Airspace:
Controlled airspace is officially defined by exclusion, which often does not
tell you much. By that reasoning, Class E airspace is controlled airspace
that is not Class A, B, C or D or G (explained below) airspace. Not too
helpful, but you can be sure that there is a lot of Class E airspace, so much
that one could think of it as "E" for Elemental or Everywhere
airspace, the airspace out of which all other types are carved. It is the
filler that fills in under Class A, ie; below
18,000' msl, and between Classes B,C
and D and over the top of Class G (described below). Its volume is vast. If
we ignore the upper cover of Class A airspace, it is safe to say that there is
a lot more E than all the other kinds combined. Ultralights fly freely in
most of Class E space with one exception described
below.
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Class E Surface Areas and
Floors
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Class E almost always has one of
four lower limits: those being surface, 700' AGL, 1200' AGL, or 14,500'
MSL (discussed below). Most of the country has a Class E lower limit of
1200' AGL. Where it drops to 700' AGL it is shown by a broad magenta line with
a fuzzy side. The fuzzy side is the side where the floor of Class E is 700'
AGL. The floor may also drop to the surface where it is called "Class E
Surface Area". A dashed magenta line indicates the boundary of the Class
E Surface Area. So on the image above at right, you
can see the dashed magenta line around the airport indicating the outer
boundary of the Class E Surface Area and outside of that a meandering wide
magenta line showing where the floor of Class E goes from 700' agl to 1200' agl as you go away
from the airport. Hover your mouse inside the image and then hold it still
and text will appear stating the floor of Class E at that point.
The major exception to ultralights being allowed in
Class E Airspace is: FAR, Part 103.17 -- "No person may operate an
ultralight vehicle within [snip] 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."
"Class E Surface Area," looks much like Class D but only in dashed magenta, not dashed blue.
Notice there is no upper altitude number within a box like there was in Class
D. The question then becomes... what is the upper limit? How is this airspace
boundary defined?
The FAA has a definition for "Class E Surface Area" that includes
an upper limit. It is the height of the surrounding Class E floor just
outside the lateral boundaries of the Class E Surface Area. For example in the image (above right), the upper limit of
Class E Surface Area is 700' agl meaning you could
fly your ultralight vehicle over this airport but you must remain at least
700' agl as you fly over. For reference on this
please go to this
FAA document.
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Remote areas of the country
sometimes have Class E that has a lower limit of 14,500' msl.
Where it borders between this level and 1200' agl
there is a shaded blue line. The 14,500' MSL side is the sharp
edged side and the fuzzy side is the 1200' AGL side.
Occasionally the floor of Class E is none of the usual
values. Where it is a discrete value it is shown by a staggered blue line. A
number in blue on the side of the line indicates the floor of Class E. If a
number is only on one side then the side missing a number is either 14,500'
MSL, 1200' AGL, 700' AGL or the surface depending on the other information on
the map.
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The image at right shows a summary
of our knowledge so far of the floor of Class E airspace. Hover your mouse
over the image and text should appear stating the floor of Class E in that
area. Give it a try!
Class
G airspace:
Class G airspace is a mantle of low lying airspace
beginning at the surface. Class G is airspace that is completely uncontrolled
and in which an ultralight flies most comfortably.
This low lying blanket of uncontrolled airspace only
ends when it meets Class B, C, D or E airspace.
Think of Class G as "ground" airspace. It covers almost the entire
country. In very remote areas it has an upper limit at 14,500' msl. However the vast majority
of area of the country it has an upper limit that follows the contour of the
ground. The top of Class G usually is where the floor of the overriding Class
E is. Like a coat of paint following the contour of the land. Sometimes the
depth of Class G is 700', some times it's 1200',
and where Class B,C,D or E extend to the surface there is no surface Class G.
Special
Use Airspace:
FAR 103.19 says we are not
allowed into Restricted or Prohibited areas.
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Restricted Area -- A restricted area
may be quite large and is shown on the sectional with a wide blue line of
hash marks and a sharp outer edge. The image at right shows several
Restricted Areas of various shapes all pieced together. Unseen hazards such
as artillery practice, missile firing and other activities may take place.
Travel in a Restricted Area may be possible when it is not activated, but
permission should be obtained by the controlling agency. Your sectional has a
table that gives the floor and ceiling of Restricted Areas as well as the
times of use and the controlling agency.
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Prohibited Area -- A prohibited area, as shown and clearly
marked with the words "Prohibited Area" on your sectional, is an
area enclosed in a unique wide blue border with a sharp outer edge. No one
flies there, neither regular aircraft nor ultralights, without specific
permission. These prohibited areas involve national security and sometimes
environmental protection. They are not to be ignored under any circumstances.
Victor Airway -- A Victor Airway is a special kind of Class E airspace.
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We are allowed to fly there but
it's a good idea to know where they are and avoid them if you wish to reduce
the amount of air traffic you are flying in. Victor Airways are like highways
in the sky. Many powered aircraft follow these routes. The routes connect
radio navigation beacons called "very high frequency omnidirectional
range" or VOR stations that radiate a signal in all directions. These
stations are usually located at or near airfields. North-south Victor Airways
have odd numbers while east-west airways have even numbers. These federal or
Victor Airways are used by both IFR and VFR aircraft. The airspace set aside
for a Victor Airway is eight miles wide with a floor at 1200 AGL; they extend
up to FL 180 (18,000' msl). Victor Airways are
shown on your sectional by faint blue lines in which is printed the V
designation along with the airway number. The image at right is of the local
Crestline area. Note the two Victor Airways that run diagonal, V-442 and
V-137. Also note the hang glider symbol (glider with an H inside a diagonal
box. And also note the communication info at the lower left which indicates
that arriving aircraft are talking to ATC on 127.25.
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Military Training Routes -- MTRs
are depicted as thin, light gray lines on the sectional. Each has its own
identification, and the identifier has two parts. "VR" means that
pilots flying the training routes will be flying under visual flight rules.
"IR" means the pilots will be flying under instrument flight rules
(look out for these guys). The second part of the identifier is either a
three or a four-digit number. Four digits means the route will be flown at or
below 1500 feet AGL, an especially dangerous level for ultralight encounters.
A three-digit number means the route will be flown both below and above 1500
feet AGL so there's a possibility that they too are to watch out for. Thus,
VR-1260 means a training route flown under VFR at a relatively low level.
IR-141 would be a route flown under IFR conditions at any level. A jet
fighter traveling toward you at over 300 miles per hour can be very hard to
see, so it's a great idea to keep any local MTRs fixed in the back of your
mind, and to be especially alert when crossing an MTR.
Warning Area -- This is a hazardous area that lies over international waters,
beyond the three mile coastal limit. Long, over
water flights by ultralights into these areas are unlikely.
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Military Operations Area (MOA) -- These
large areas of the country are shown on your sectional as enclosed by a line
of magenta hash marks with a sharp outer edge. Military operations such as
training exercises come and go. Permission to fly in an
MOA is not required, but a pilot may determine the hours of any current
activity by calling the nearest Flight Service Station (FSS). Dial
1-800-WXBRIEF.
Alert Area -- Bordered the same as a Restriced and
Prohibited area, the identifier is not with a R or P but with an A. We are
allowed into Alert Area without prior permission. An Alert Area may involve
high general aviation traffic, unusual air operations or frequent student
training. The area will be marked with a blue border with a word or two of
explanation.
Things Change -- Presidents and other important people who require high
security show up everywhere from time to time, air shows open and close,
natural disasters (like forest fires) suddenly command attention, runways
close for repairs, etc. Be aware of current events in your area, events that
might change airspace demands. If you have a question, a call to your local
Flight Service Station will answer it. 1(800) WX-BRIEF. Ask for any NOTAMS
that may affect flying under Part 103. An online source for Temporary Flight
Restrictions is available at this website.
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