Questions on VFR sectionals and TACs

There are some mysteries that I've encountered while learning to read
VFR charts:

1. I see airports with dashed cyan circles around them that I presume
indicate Class D airspace (based on the chart legend). However, the
circles are not always the same size, and I don't see any indication
of their radii; how do I determine how far out the Class D circle
extends (short of measuring it by hand)? Also, is there a convention
for the center of the Class D circle (tower, or whatever?)? They
don't seem to be centered on anything easily identifiable.

2. The legend doesn't appear to explain lines that consist of a solid
cyan line with cyan dots inside. It seems to outline things like
wildlife refuges or parks and stuff like that. Is this just an extra
line style used for things that don't otherwise have line styles
assigned, or what? Are there any restrictions or other things to know
about spaces enclosed by these lines, or are they for information
only?

3. I'm confused about Class E airspace. If I understand correctly,
the absence of any other indication on the chart means that Class E
starts at 1200' AGL, and extends to 18,000' MSL. If the shaded purple
border encloses an area, it's Class E starting at 700' AGL and still
extending to 18,000' MSL. If it's a shaded cyan border, it means ...
Class E starts at 1200' AGL and extends to 18,000' MSL?? (The chart
says "abuts Class G," but I'm not sure what they mean.)

4. The cyan chain-link Class E border confuses me. Which side is
inside the Class E? The altitude is the floor of the Class E and it
still extends to 18,000' MSL, right? If there are different altitudes
on each side of the chain link, what does that mean, and where do I
look for the other border of the airspace? For example, just west of
Buckeye on the Phoenix sectional, there are chain links and stuff all
over the place, and I'm having trouble figuring out what the floors
are and where. Around Western Sky airport (W 113° 40' N 33° 46'
roughly), I see the shaded cyan border for Class E at 1200' AGL, but
in that area I see 7000 MSL, and a chain link on the right and bottom.
There are chain links next to airways, too. I don't know which
altitude applies where.

Can anyone explain the above to me?

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Mxsmanic wrote:
There are some mysteries that I've encountered while learning to read
VFR charts:

1. I see airports with dashed cyan circles around them that I presume
indicate Class D airspace (based on the chart legend). However, the
circles are not always the same size, and I don't see any indication
of their radii; how do I determine how far out the Class D circle
extends (short of measuring it by hand)? Also, is there a convention
for the center of the Class D circle (tower, or whatever?)? They
don't seem to be centered on anything easily identifiable.

Dashed cyan is actually class E surface area. Class D surface is dashed
blue. The configuration of the airspace depends on the instrument
approaches at that airport. If you need to know the radius, you can
measure it by hand, but I don't see how that information is useful for
VFR navigation. You just need to know the boundaries of the airspace,
not the radius from an aribtrary center location.



2. The legend doesn't appear to explain lines that consist of a solid
cyan line with cyan dots inside. It seems to outline things like
wildlife refuges or parks and stuff like that. Is this just an extra
line style used for things that don't otherwise have line styles
assigned, or what? Are there any restrictions or other things to know
about spaces enclosed by these lines, or are they for information
only?

Yes that is the boundaries of wildlife refuges and national parks. You
need to stay 2000ft above the terrain. This information can be found on
the inside flap of the chart, not in the standard legend box.



3. I'm confused about Class E airspace. If I understand correctly,
the absence of any other indication on the chart means that Class E
starts at 1200' AGL, and extends to 18,000' MSL. If the shaded purple
border encloses an area, it's Class E starting at 700' AGL and still
extending to 18,000' MSL. If it's a shaded cyan border, it means ...
Class E starts at 1200' AGL and extends to 18,000' MSL?? (The chart
says "abuts Class G," but I'm not sure what they mean.)


This is a very typical confusion. Class E begins at 700' inside the
shaded magenta borders. It begins at 1200' inside the shaded blue
borders. It begins at 14500' outside the shaded blue borders. Now, you
may not see any shaded blue borders on your chart because you may be
completely surrounded by it. So there is no way to know whether you are
inside or outside these borders, but since the majority of the U.S. is
surrounded by these blue borders it is safe to assume that you are
inside. If you go to parts of western U.S. or coastal areas you will
see the blue borders. The top of the class E is 18000' where class A
begins.



4. The cyan chain-link Class E border confuses me. Which side is
inside the Class E? The altitude is the floor of the Class E and it
still extends to 18,000' MSL, right? If there are different altitudes
on each side of the chain link, what does that mean, and where do I
look for the other border of the airspace? For example, just west of
Buckeye on the Phoenix sectional, there are chain links and stuff all
over the place, and I'm having trouble figuring out what the floors
are and where. Around Western Sky airport (W 113° 40' N 33° 46'
roughly), I see the shaded cyan border for Class E at 1200' AGL, but
in that area I see 7000 MSL, and a chain link on the right and bottom.
There are chain links next to airways, too. I don't know which
altitude applies where.


In some areas it may not be useful to define class E as beginning at
1200' or 700' AGL because the terrain may be uneven, or there may be a
need to define class E as beginning at something other than 1200 or
700. This is where the blue chainlink is used. It is hard to tell
whether you are inside of ourside the line, but it should become
apparent once you identify the boundaries.

"Andrew Sarangan" wrote in message
oups.com...

Dashed cyan is actually class E surface area. Class D surface is
dashed blue.


Dashed cyan is a Class D surface area, a Class E surface area is dashed
magenta.

Andrew Sarangan wrote:


Dashed cyan is actually class E surface area. Class D surface is dashed
blue.

Cyan is blue-green. The other color is magenta (red-blue).

Andrew Sarangan writes:

Dashed cyan is actually class E surface area. Class D surface is dashed
blue.

The legend on the chart I'm looking at says the opposite. Magenta
dashed lines are marked as Class E; cyan dashed lines are marked as
Class D.

The configuration of the airspace depends on the instrument
approaches at that airport. If you need to know the radius, you can
measure it by hand, but I don't see how that information is useful for
VFR navigation. You just need to know the boundaries of the airspace,
not the radius from an aribtrary center location.

It's just hard to figure out whether I'm inside or outside the
boundaries without a radius and center point. IIRC, I need to contact
the tower before entering the Class D space (?).

Yes that is the boundaries of wildlife refuges and national parks. You
need to stay 2000ft above the terrain. This information can be found on
the inside flap of the chart, not in the standard legend box.

OK, I found it in the fine print (I'm looking at SkyVector).

This is a very typical confusion. Class E begins at 700' inside the
shaded magenta borders. It begins at 1200' inside the shaded blue
borders. It begins at 14500' outside the shaded blue borders. Now, you
may not see any shaded blue borders on your chart because you may be
completely surrounded by it. So there is no way to know whether you are
inside or outside these borders, but since the majority of the U.S. is
surrounded by these blue borders it is safe to assume that you are
inside. If you go to parts of western U.S. or coastal areas you will
see the blue borders. The top of the class E is 18000' where class A
begins.

OK, thanks, that clarifies things.

In some areas it may not be useful to define class E as beginning at
1200' or 700' AGL because the terrain may be uneven, or there may be a
need to define class E as beginning at something other than 1200 or
700. This is where the blue chainlink is used. It is hard to tell
whether you are inside of ourside the line, but it should become
apparent once you identify the boundaries.

OK. I confess that I don't see the logic behind so many changes in
Class E altitudes; some people at the FAA must have a lot of time on
their hands.

--
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Mxsmanic wrote:
Andrew Sarangan writes:

Dashed cyan is actually class E surface area. Class D surface is dashed
blue.

The legend on the chart I'm looking at says the opposite. Magenta
dashed lines are marked as Class E; cyan dashed lines are marked as
Class D.


Blue is class D and purple of class E. I was thinking of purple when
you said cyan. I guess I have to go back and relearn my colors.

Mxsmanic writes:
In some areas it may not be useful to define class E as beginning at
1200' or 700' AGL because the terrain may be uneven, or there may be a
need to define class E as beginning at something other than 1200 or
700. This is where the blue chainlink is used. It is hard to tell
whether you are inside of ourside the line, but it should become
apparent once you identify the boundaries.

OK. I confess that I don't see the logic behind so many changes in
Class E altitudes; some people at the FAA must have a lot of time on
their hands.

I've assumed that the reason for doing this is to identify areas in
which you can expect to find IFR planes. I would guess that you don't
want to have IFR planes going through areas too low or far away from
antennas to have radio communications with ATC. (Could someone
correct me if my guess is wrong?)

Chris

Christopher Brian Colohan writes:

I've assumed that the reason for doing this is to identify areas in
which you can expect to find IFR planes. I would guess that you don't
want to have IFR planes going through areas too low or far away from
antennas to have radio communications with ATC. (Could someone
correct me if my guess is wrong?)

Isn't IFR allowed in both Class E and Class G?

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Mxsmanic,

Isn't IFR allowed in both Class E and Class G?


Yes, but along an airway or and approach, IFR traffic is much more
likely.

--
Thomas Borchert (EDDH)

I've assumed that the reason for doing this is to identify areas in
which you can expect to find IFR planes. I would guess that you don't
want to have IFR planes going through areas too low or far away from
antennas to have radio communications with ATC. (Could someone
correct me if my guess is wrong?)

Not where you can expect to find IFR planes, but where you can
expect NOT to find VFR planes if the weather is below minimums.