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Airspace
Let's take a look at airspace and how each is seen on Sectional Charts
Overview
As seen above, in this all-to-common image (this one taken from
the 2005 AIM), certain airspaces look quite a bit like up-side-down wedding
cakes
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Around Towered/Busy airports, class Bravo airspace extends
from the surface up to 10,000 feet MSL.
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There are 'shelves' in class Bravo airspace whose bases move
progressively higher the farther out from an airport they are positioned
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Around Towered/Congested airports, class Charlie airspace
extends from the surface up to 4,000 feet MSL.
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Much like Class Bravo, there are 'shelves' in class Charlie
airspace whose bases move progressively higher the farther out from an
airport they are positioned
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The rest of controlled airspace is classified as class Echo
which can extend from the surface to 18,000 feet MSL.
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Normally class Echo airspace starts at either 700 or 1,200
AGL, but in some special circumstances, it can start at the surface.
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Uncontrolled airspace is classified as class Golf
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Can extend from the surface up to 14,500 feet MSL.
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Also exists below class Echo airspace whose base begins at
700 or 1,200 feet AGL
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Military Operation Areas
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Restricted Areas
Class Alpha (A)
As you probably already know (or maybe not), Class Alpha (A)
airspace is not shown on aeronautical charts. Here are some
characteristics of Class Alpha airspace
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The base of Class Alpha airspace is always 18,000 Feet MSL
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Class Alpha height is FL600 (60,000 feet)
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An aircraft flying in Class Alpha must be certified for IFR
flight
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To fly in class Alpha airspace an IFR flight plan MUST be
filed
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Weather Minimums
Class Bravo (B)
Class Bravo means 'BIG'!!! Large aircraft, Very busy airports, places
where general aviation planes are normally not flown.
 To
get into class Bravo airspace, you have to be cleared and able to follow ATC
directions to the 'T'.
The familiar (familiar to northern California pilots) San Francisco Class
Bravo airspace is shown here to the left. The airspace is layered sort of
like an up-side down wedding cake using heavy Blue (Big-Blue, Bravo-Blue) lines.
The layer in the center is shown as Class Bravo airspace from the surface to
10,000 feet (100/SFC). The next layer south of the airport is from 4,000
feet to 10,000 feet (100/40). The area to the west of the airport is 2,100
feet up to 10,000 feet (100/21). The base of the class bravo rises higher
as you travel away from the airport.
Class Bravo airspace also contains a Mode-C veil. This area around the
airport is 30 nautical miles in radius (60 nautical mile diameter) and 10,000
feet high where all aircraft MUST have an operable transponder with automatic
altitude reporting capabilities. This mode-C veil is shown as a solid
magenta line around the class Bravo airspace
Some characteristics of Class Bravo airspace:
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Memory trick for Bravo: Big-Blue!
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The base of Class Bravo airspace is depicted on navigation
charts
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100/30 = 10,000 height/3,000 base
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50/SFC = 5,000 height/To the Surface
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Class Bravo height is 10,000 feet MSL
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An ATC clearance is required before entering class Bravo
airspace
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A Two-way radio is required
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A Transponder with altitude reporting capabilities is
required
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Only private pilots or above are allowed into class Bravo
airspace. Student pilots are allowed in if trained and endorsed for
that particular airspace by a CFI
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Weather Minimums
Class Charlie (C)
Class Charlie airspace - 'Congested' airspace surrounds most busy airports
that have an operating control tower, radar approach control and IFR operations.
Notice north/north-east of the San Francisco airport shown above is the Oakland airport. This
airport is surrounded by class Charlie airspace (Dark Magenta Lines) and
underlies the class Bravo airspace of San Francisco.
Some characteristics of Class Charlie airspace
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Memory trick for Delta: I haven't figured one out yet
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The base of Class Charlie airspace is depicted on navigation
charts
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100/21 = 10,000 height/2,100 base
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T/SFC = Base of overlying airspace to the surface
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Class Charlie height is 4,000 feet MSL
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A Two-way radio is required
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A Transponder with altitude reporting capabilities is
required
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Two-way radio communication with the controlling agency is
required during entry into class Charlie airspace
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Normally, when departing and airport in class Charlie
airspace, you will be given a departure clearance that you are expected to
follow
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Weather Minimums
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Visibility: 3 Statute Miles
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Distance from Clouds: 1,000 feet above, 2,000 feet
horizontal, 500 feet below (1,2,5 rule)
Class Delta (D)
Class delta airspace is airspace surrounding a towered airport from the
surface to 2,500 feet AGL above that airport. These are controlled
airports, usually by a control tower. There is traffic, but not as much as
class Charlie or Bravo airspace.
Some characteristics of Class Delta airspace
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Memory trick for Delta: Dotted-Blue!
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Always towered airports
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Top of airspace is normally shown within a 'dotted' blue box
inside the airspace (in this case, 2,900 feet MSL)
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Two way radio contact is required
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Weather Minimums
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Visibility: 3 Statute Miles
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Distance from Clouds: 1,000 feet above, 2,000 feet
horizontal, 500 feet below (1,2,5 rule)
Class Echo (E)
All 0ther airspace that is controlled and not Class Alpha, Bravo, Charlie or
Delta is identified as Class
 Echo
(Everything-Else). The floor of class echo airspace normally starts at
12,000 feet AGL and extends upward to 17,999 feet MSL. Near airports,
class Echo airspace starts at 700 feet AGL.
Class echo airspace is identified by a shaded magenta bar around airports and
other areas on a sectional chart. The lighter portion of the magenta
depicts class Echo airspace beginning at 700 feet AGL while the more solid
portion of the bar shows class Echo airspace starting at 1,200 feet AGL.
Notice that Class echo begins lower to the ground nearer airports than away from
airports - for obvious reasons.
Changes in class Echo airspace that is not near airports are shown
using Differentiation lines (or 'Zipper' lines) on sectional charts. These
lines of differentiation indicate two things: 1) The base of class Echo
airspace has changed; 2) Class Echo bases are now measured in feet MSL instead
of feet AGL.
 As shown here to the right, the Differentiation lines show that the area
inside of the triangle has a floor of class Echo airspace that begins at 7,500
feet MSL instead of the normal 1,200 feet AGL. This might be because of
mountains or other obstructions that the FAA wants to keep you clear of.
If not noted on the chart, the areas outside of these differentiation lines go
back to the normal AGL measurements of class Echo airspace.
Class Echo differential lines can also interact with Class Echo/Golf
demarcation lines as well. As shown below, the class Echo differentiation
lines attach to the Echo/Golf demarcation lines.
This means that class Golf goes up to 14,500 from the ground
inside the shaded lines, but class Echo exists within the 'zippered' lines as
indicated MSL. Outside of the 'zippered' areas, class Echo is again 1,200
AGL (or 700 AGL as indicated).
There are some other 'special' class Echo airspaces which can be
 depicted
around airports. These areas are depicted as Class Echo airspace from the
base of the surrounding class echo airspace to the ground.
As can be seen here, there are two circled areas that contain magenta colored
dotted lines near the class Delta airspace. These magenta lines indicate
that the class Echo airspace around the airport goes from the base of the
surrounding class Echo airspace (700 feet in this case) all the way to the
ground. The ceiling of the class Echo airspace again goes all the way up
to 17,999 feet MSL.
In this drawing, there are two areas that are class Echo airspace to the
ground. The reason for this is that aircraft are coming in for landings at
the indicated runways quite often, so this adds additional protection the
airspace surrounding the class Delta airspace for this particular airport.
Characteristics of class Echo airspace include:
Class Golf (G)
If an airspace is not A-E, it is class Golf. Class Golf is uncontrolled
airspace and is any airspace that is not depicted as either A, B, C, D or E.
As depicted on a sectional chart, Class Golf and Class Echo are
differentiated by a blue shaded bar as
shown to the right. If you notice, the lighter shaded area of the blue bar
indicates class Echo airspace on that side of the bar. The darker shaded,
or solid portion of the bar indicates class Golf airspace from the surface to
14,500 feet MSL.
Characteristics of class Golf airspace include:
Weather Minimums in summary
This table was taken from the 2005 AIM
Special Use Airspace
Prohibited Areas
These types of areas indicated where aircraft MUST NOT travel
through. These types of areas are established for security reasons.
Restricted Areas
Areas where flight is not prohibited, but could be restricted to
certain parameters. These areas often contain unusual and often invisible
hazards to aircraft (explosions, artillery, guided missiles, extra-galactic
aliens).
Do not enter these areas unless the controlling agency allows
you to enter.
The restricted area shown here to the right is the Tracy
restricted area which is part of the Livermore laboratory in Livermore
California. The restricted area is circled in red and has a
 desgination
number of R-2531. This Blue-hatched pattern can be used to designate
Prohibited, Restricted and Warning areas. You can find this information at
the top of the chart as shown below.
This area is restricted up to (but not including) 4,000 feet MSL
with the listed times of use.
Warning Areas
This is airspace three nautical miles from the coast of the US
into ocean areas. Hazardous activity to non-participating aircraft can be
found in this zone around the U.S.
Military Operations Areas
MOAs are airspace where military operations may be taking place.
VFR aircraft can enter these areas, but must be very cautious for other aircraft
since these may be moving at high speed. MOAs are actually setup to
separate IFR traffic from participating aircraft.
The Maxwell 2 MOA (shown on the right) is an area in northern
California that might have military aircraft operating. Notice how the
airspace doesn't really tell you anything about the area, but is identified by
magenta hatched lines encircling the MOA.
As shown above, the MOA information can be found at the top of
the sectional chart which shows the MOA.
This page was last modified on
12/03/2006
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