class C and B comms on sectionals?

In the legend on sectional charts there are a number of frequencies
listed for the various class B and C airspaces and airports.

For example, the northern florida chart has jacksonville listed as
"120.75 (091-180)". Now, during my commercial checkride a month ago my
examiner asked me what the numbers in parenthesis were and I said they
were courses from that C-airspace primary airport. So if you would draw
lines from Jacksonville international and out on a magnetic course of
091 and 180 degrees, you would have as a result a pie-shaped sector on
the chart. If you're approaching the C-airspace and your location is
withing that pie-sector you should use 120.75 Mhz to get your clearance
to enter the airspace.

There is also a small COMMs box on the chart itself located southeast
of the airspace so that makes sense to me.

However, my examiner said that 091-180 in the legend are in fact
RADIALS. The airspace in question on my checkride was the B airspace
around orlando, and she said these numbers are radials from (in that
case) ORL VOR and not courses from the airport.

1. Why would they use VOR radials for this on a VFR chart, when a VOR
isn't even required for VFR flight?

2. The C airspace set up for Jacksonville international doesn't even
have a VOR.


Is there a source where I can get more information on the legend that
the sectionals have?

The Aeronautical Chart User's Guide? I couldn't find anything in it that
helps, though.

Bob Gardner

"Magnus" wrote in message
...
In the legend on sectional charts there are a number of frequencies
listed for the various class B and C airspaces and airports.

For example, the northern florida chart has jacksonville listed as
"120.75 (091-180)". Now, during my commercial checkride a month ago my
examiner asked me what the numbers in parenthesis were and I said they
were courses from that C-airspace primary airport. So if you would draw
lines from Jacksonville international and out on a magnetic course of
091 and 180 degrees, you would have as a result a pie-shaped sector on
the chart. If you're approaching the C-airspace and your location is
withing that pie-sector you should use 120.75 Mhz to get your clearance
to enter the airspace.

There is also a small COMMs box on the chart itself located southeast
of the airspace so that makes sense to me.

However, my examiner said that 091-180 in the legend are in fact
RADIALS. The airspace in question on my checkride was the B airspace
around orlando, and she said these numbers are radials from (in that
case) ORL VOR and not courses from the airport.

1. Why would they use VOR radials for this on a VFR chart, when a VOR
isn't even required for VFR flight?

2. The C airspace set up for Jacksonville international doesn't even
have a VOR.


Is there a source where I can get more information on the legend that
the sectionals have?

The radial from the VOR merely defines the airspace for that frequency. It
does not require that you use the VOR in flight to determine whether you are
in that space or not. The same is true for defining TSAs and many restricted
or prohibited airspace.

Relate the information to your sectional and then determine your position
relative to that airspace via normal pilotage.

--
-------------------------------
Travis
"Magnus" wrote in message
...
In the legend on sectional charts there are a number of frequencies
listed for the various class B and C airspaces and airports.

For example, the northern florida chart has jacksonville listed as
"120.75 (091-180)". Now, during my commercial checkride a month ago my
examiner asked me what the numbers in parenthesis were and I said they
were courses from that C-airspace primary airport. So if you would draw
lines from Jacksonville international and out on a magnetic course of
091 and 180 degrees, you would have as a result a pie-shaped sector on
the chart. If you're approaching the C-airspace and your location is
withing that pie-sector you should use 120.75 Mhz to get your clearance
to enter the airspace.

There is also a small COMMs box on the chart itself located southeast
of the airspace so that makes sense to me.

However, my examiner said that 091-180 in the legend are in fact
RADIALS. The airspace in question on my checkride was the B airspace
around orlando, and she said these numbers are radials from (in that
case) ORL VOR and not courses from the airport.

1. Why would they use VOR radials for this on a VFR chart, when a VOR
isn't even required for VFR flight?

2. The C airspace set up for Jacksonville international doesn't even
have a VOR.


Is there a source where I can get more information on the legend that
the sectionals have?

That doesn't make any sense to me. So which VOR am I supposed to use
for Jacksonvill Intl. then? It doesn't havve a VOR anywhere in the C
airspace. The only VOR in that entire region is Craig, but that's not
even close to jacksonville.

It doesn't make sense to me to have a chart that defines COMM areas
based on VORs when the chart is for VFR flights only.

If I'm flying to Jacksonville VFR I won't have a VOR to use as my point
of reference because there's none there.

Why would the makers of the chart even consider using radiostations,
all that matters is to have a point of reference from which the courses
should be drawn so you can identify which fq you should contact
approach on, and from that viewpoint using the actual airport makes
more sense than some VOR that might or might not be there.

More importantly, I have NOT found any information that actually states
how the legend on the sectional was meant to be used. Surely there must
be some source of information for these charts detailing how they
should be used? How do examiners and instructors determine that these
numbers next to the frequencies are from VORs? There's nothing on the
chart legend that suggest it.


On 2004-04-24 08:48:20 -0400, "Travis Marlatte"
said:

The radial from the VOR merely defines the airspace for that frequency. It
does not require that you use the VOR in flight to determine whether you are
in that space or not. The same is true for defining TSAs and many restricted
or prohibited airspace.

Relate the information to your sectional and then determine your position
relative to that airspace via normal pilotage.

"Magnus" wrote in message
...

In the legend on sectional charts there are a number of frequencies
listed for the various class B and C airspaces and airports.

For example, the northern florida chart has jacksonville listed as
"120.75 (091-180)". Now, during my commercial checkride a
month ago my examiner asked me what the numbers in
parenthesis were and I said they were courses from that C-airspace
primary airport. So if you would draw lines from Jacksonville
international and out on a magnetic course of 091 and 180 degrees,
you would have as a result a pie-shaped sector on the chart. If
you're approaching the C-airspace and your location is withing
that pie-sector you should use 120.75 Mhz to get your clearance
to enter the airspace.

There is also a small COMMs box on the chart itself located southeast
of the airspace so that makes sense to me.

However, my examiner said that 091-180 in the legend are in fact
RADIALS. The airspace in question on my checkride was the B
airspace around orlando, and she said these numbers are radials
from (in that case) ORL VOR and not courses from the airport.

1. Why would they use VOR radials for this on a VFR chart,
when a VOR isn't even required for VFR flight?

2. The C airspace set up for Jacksonville international doesn't
even have a VOR.


Is there a source where I can get more information on the legend that
the sectionals have?


The A/FD doesn't have any additional information. I don't recall seeing
anything that actually stated these were bearings from the field, but, like
you, I always assumed they were. Obviously, they can't be radials in
airspace without VORs, so to be consistent they'd have to be bearings from
the field. In the case of ORL, it wouldn't make a difference as the VOR is
on the field. I would've asked the examiner for her source on that.

"Travis Marlatte" wrote in message
news

The radial from the VOR merely defines the airspace for that
frequency. It does not require that you use the VOR in flight
to determine whether you are in that space or not. The same is
true for defining TSAs and many restricted or prohibited airspace.


What's a TSA?

"Magnus" wrote in message
...

That doesn't make any sense to me. So which VOR am I supposed
to use for Jacksonvill Intl. then? It doesn't havve a VOR anywhere
in the C airspace. The only VOR in that entire region is Craig, but
that's not even close to jacksonville.

It doesn't make sense to me to have a chart that defines COMM
areas based on VORs when the chart is for VFR flights only.

If I'm flying to Jacksonville VFR I won't have a VOR to use as
my point of reference because there's none there.

Why would the makers of the chart even consider using radiostations,
all that matters is to have a point of reference from which the courses
should be drawn so you can identify which fq you should contact
approach on, and from that viewpoint using the actual airport makes
more sense than some VOR that might or might not be there.

More importantly, I have NOT found any information that actually
states how the legend on the sectional was meant to be used.
Surely there must be some source of information for these charts
detailing how they should be used? How do examiners and
instructors determine that these numbers next to the frequencies
are from VORs? There's nothing on the chart legend that suggest
it.


Some facilities don't use bearings at all. Madison approach splits East and
West, and that's how it's indicated in the frequency tab on the sectional.
The Letter of Agreement with Chicago Center designates the division as the
extended centerlines of runway 18/36. They could have used VOR radials, I
suppose, as Madison VOR is on the field. But they didn't. More anecdotal
evidence that these are not radials.

A little more info:

This is all from the Chicago Sectional.

There are three VOR's located inside the Chicago Class B. The frequency
split (in degrees) is: 360 - 179, and 180 - 359.

The split for the Madison Class C is East and West.

The split for the Milwaukee Class C is Southeast and Northwest.

The split for the Moline Class C is S/SE of active runway and N/NE of active
runway.

And finally, the split for the Muskegon TRSA is N of V2 (low altitude
airway) and S of V2.

Given all of this, I think it would be a safe bet that these splits are NOT
based on VOR radials, and the level of precision required is very low.


"Magnus" wrote in message
...
That doesn't make any sense to me. So which VOR am I supposed to use
for Jacksonvill Intl. then? It doesn't havve a VOR anywhere in the C
airspace. The only VOR in that entire region is Craig, but that's not
even close to jacksonville.

It doesn't make sense to me to have a chart that defines COMM areas
based on VORs when the chart is for VFR flights only.

If I'm flying to Jacksonville VFR I won't have a VOR to use as my point
of reference because there's none there.

Why would the makers of the chart even consider using radiostations,
all that matters is to have a point of reference from which the courses
should be drawn so you can identify which fq you should contact
approach on, and from that viewpoint using the actual airport makes
more sense than some VOR that might or might not be there.

More importantly, I have NOT found any information that actually states
how the legend on the sectional was meant to be used. Surely there must
be some source of information for these charts detailing how they
should be used? How do examiners and instructors determine that these
numbers next to the frequencies are from VORs? There's nothing on the
chart legend that suggest it.


On 2004-04-24 08:48:20 -0400, "Travis Marlatte"
said:

The radial from the VOR merely defines the airspace for that frequency.
It
does not require that you use the VOR in flight to determine whether you
are
in that space or not. The same is true for defining TSAs and many
restricted
or prohibited airspace.

Relate the information to your sectional and then determine your
position
relative to that airspace via normal pilotage.

"Bill Denton" wrote in message
...

The split for the Madison Class C is East and West.

The split for the Milwaukee Class C is Southeast and Northwest.


Milwaukee's split, like Madison's, is along the extended runway centerline.
Madison's is fixed along runway 18/36, but Milwaukee's varies with runway
usage. Sometimes it's along runway 7/25, sometimes it's along runway 1/19.

"Magnus" wrote in message
...
[...]
1. Why would they use VOR radials for this on a VFR chart, when a VOR
isn't even required for VFR flight?

Someone else answered that. You don't need a VOR receiver to be able to
know where a VOR radial is, when flying VFR.

2. The C airspace set up for Jacksonville international doesn't even
have a VOR.

Is there a source where I can get more information on the legend that
the sectionals have?

I'm still trying to figure out why it matters. At an airport without a VOR,
obviously they cannot be radials from the VOR. At an airport with a VOR,
the difference between a radial and a bearing from the airport is, for the
purposes of determining which frequency to use for ATC, inconsequential. If
you are so close to the radial/bearing that it makes a difference, the right
frequency to use is the one for the sector you're about the fly into,
regardless of which side of which boundary you happen to be on.

The only boundary case I can see even coming close to mattering is if you
happen to be flying inbound or outbound right smack on the boundary itself.
My guess is that in that case, ATC doesn't care which sector you contact.
If they do, it is easy enough for them to send you over to the correct one,
if you happen to choose the wrong one.

If I had to guess, I'd guess it's bearing from the airport, for the reasons
pointed out already (that defining it as VOR radials would be meaningless at
an airport without a VOR). But in reality, the sectors can be chopped up
differently from what's on the chart anyway, due to those pesky letters of
agreement. Use the chart as a guideline as best you can, and if you get it
wrong, no big deal. ATC will straighten things out.

Pete