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?

--
Transpose mxsmanic and gmail to reach me by e-mail.

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.

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.

The nominal diameter is 4.3 NM (5 SM). There
may be extensions either as class D or class E surface area that
accomodate the instrumetn approaches. They're centered on the
airport reference point.


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?


Symbols are explained more in the Aeronautical Chart User's Guide.
http://www.naco.faa.gov/index.asp?xm...ine/aero_guide

The blue line with the dots indicates a conservation area (wilelife
refuge, national park ,etc.).

Pilots are requested to stay 2000' above these (but it's not
mandatory).

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.)

Originally there was a lot less controlled airspace than there is
now. If you're out in parts of the country which is much more
desolate you'll fine the 1200' floors under airway, and the 700'
floors around airports that have instrument approaches that don't
have class E to the ground (transition areas). In most places
now, the 1200 stuff pretty much just overlaps everything and there
are magenta vignettes to take it down to 700'.

Originally, the magenta vignette was abutted with a blue vignette
showing the step up to 1200. Now they don't show the blue vignette
when it's bumping up against 700' or surface area boundaries, only
when it bumps up against uncontrolled airspace.



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.

The zig/zag class E borders are used only in bizarre mountainous
area. The side with the text is the non-standard controlled
airspace floor.

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.

--
Transpose mxsmanic and gmail to reach me by e-mail.

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

Ron Natalie writes:
Symbols are explained more in the Aeronautical Chart User's Guide.
http://www.naco.faa.gov/index.asp?xm...ine/aero_guide

The blue line with the dots indicates a conservation area (wilelife
refuge, national park ,etc.).

Pilots are requested to stay 2000' above these (but it's not
mandatory).

North of Boston you will find a large white-ground circle outlined by
a thick cyan dashed line.

The meaning of white ground or a thick cyan dashed line is not defined
in the chart legend, nor is it defined in the book you point at. Any
guess what this is? (And why the FAA thinks it is worth putting on
the chart, but not worth documenting what it means?)

Chris

In article ,
Christopher Brian Colohan wrote:

North of Boston you will find a large white-ground circle outlined by
a thick cyan dashed line.

Not anymore (look at the 74th edition of the NY sectional)


The meaning of white ground or a thick cyan dashed line is not defined
in the chart legend, nor is it defined in the book you point at. Any
guess what this is? (And why the FAA thinks it is worth putting on
the chart, but not worth documenting what it means?)

On the 73rd edition of the NY sectional there is indeed a note
that P-67 is expanded by special notam.

--
Bob Noel
Looking for a sig the
lawyers will hate