Where are the lines on charts?

L

Lindberg

Final Approach
Joined
Sep 25, 2013
Messages
7,657
Location
North Texas
Display Name
Display name:
Lindberg
Or more specifically, where are the lines IRL that are depicted on charts? For example does Class B airspace begin at the outer edge of the line? Middle? Inside?
 
I was about to post, "If you have to ask . . ."

Sent from my SM-N960U using Tapatalk
 
If you don't know, you could just say so....;)

If it makes anyone feel better, pretend my example was Class E or a TRSA.
 
Most airports have a nominal measurement in mileage of their airspace size . Get out your plotter and find out
 
IMO if you’re within just a couple miles of the estimated boundary, you’re too close if you’re not talking with ATC.
 
There is probably an answer to your question somewhere. But a safe assumption is that the lines are drawn precisely centered where the boundaries lie and the only variable is the width of the line. In other words the center of the line... But as eluded to above, for Controlled Airspace, it's probably not a good idea to get close enough for it to matter....
 
Lindberg said:
Or more specifically, where are the lines IRL that are depicted on charts? For example does Class B airspace begin at the outer edge of the line? Middle? Inside?
Click to expand...

Outer edge.
 
The lines are .2 miles wide of a sectional chart for the thick Bravo airspace delineator or about 1000 feet. If you are touching it, you are close enough to argue incursion.
 
When you feel the pucker...your close...when it gets wet...to far.
 
Honestly this is like asking what part of the aircraft constitutes an airspace violation, the wingtip or the fuselage?
 
Lindberg said:
If you don't know, you could just say so....;)

If it makes anyone feel better, pretend my example was Class E or a TRSA.
Click to expand...

If I zoom in on ForeFlight on the sectional, the line measures about 1500ft. But if I zoom in on the aeronautical map, the line just keeps getting smaller. So go back to basic geometry definitions of a line that says (paraphrasing) a line has no width. That answer your question?
 
ATC radar is sometimes less than perfectly "calibrated", as well. I'm in the FRZ and SFRA in DC; closer than a mile feels too close to me. Two miles is more than enough room, however. Then again, I'm talking to them.
 
Man, doesn’t ANYBODY read JO 7400.11C for fun anymore?

https://www.faa.gov/regulations_pol...fm/go/document.information/documentID/1034252

If you really want to know the airspace boundaries, that’s the place to look. An example for one of the areas of the PHL Class B:

“Area A. That airspace extending upward from the surface to and including 7,000 feet MSL within an 8-mile radius of the Philadelphia International Airport (PHL), excluding that airspace bounded by a line beginning at the intersection of the PHL 8-mile radius and the 002° bearing from PHL, thence direct to lat. 39°56'14'' N., long. 75°12'11'' W., thence direct to lat. 39°55'40'' N., long. 75°08'31'' W., thence direct to the intersection of the PHL 8-mile radius and the 061° bearing from PHL, and that airspace within and underlying Areas B and C hereinafter described.”

Granted, not all of them are quite so complicated, especially Class D’s:

AGL MI D Saginaw, MI
MBS International Airport, MI
(lat. 43°31'59'' N., long. 84°04'47'' W.)
That airspace extending upward from the surface to and including 3,200 feet MSL within a 4.8- mile radius of MBS International Airport.

Enjoy some light reading!
 
RussR said:
Man, doesn’t ANYBODY read JO 7400.11C for fun anymore?

https://www.faa.gov/regulations_pol...fm/go/document.information/documentID/1034252

If you really want to know the airspace boundaries, that’s the place to look. An example for one of the areas of the PHL Class B:

“Area A. That airspace extending upward from the surface to and including 7,000 feet MSL within an 8-mile radius of the Philadelphia International Airport (PHL), excluding that airspace bounded by a line beginning at the intersection of the PHL 8-mile radius and the 002° bearing from PHL, thence direct to lat. 39°56'14'' N., long. 75°12'11'' W., thence direct to lat. 39°55'40'' N., long. 75°08'31'' W., thence direct to the intersection of the PHL 8-mile radius and the 061° bearing from PHL, and that airspace within and underlying Areas B and C hereinafter described.”

Granted, not all of them are quite so complicated, especially Class D’s:

AGL MI D Saginaw, MI
MBS International Airport, MI
(lat. 43°31'59'' N., long. 84°04'47'' W.)
That airspace extending upward from the surface to and including 3,200 feet MSL within a 4.8- mile radius of MBS International Airport.

Enjoy some light reading!
Click to expand...

So is the center of the radius from the middle of the runway or the edge of the runway?
 
eman1200 said:
So is the center of the radius from the middle of the runway or the edge of the runway?
Click to expand...

Each entry gives the coordinates of whatever is being measured to. I didn't paste that part of the entry for the first example. In the second example I gave, the "airport" is considered to be "at" the coordinates given in the heading (known as the Airport Reference Point). So, 4.8 nm radius of 43 31 59N, 84 04 47W.
 
RussR said:
Each entry gives the coordinates of whatever is being measured to. I didn't paste that part of the entry for the first example. In the second example I gave, the "airport" is considered to be "at" the coordinates given in the heading (known as the Airport Reference Point). So, 4.8 nm radius of 43 31 59N, 84 04 47W.
Click to expand...

I was just messin around, Russ. besides, I don't speak lat/lon.
 
It was actually
RussR said:
Man, doesn’t ANYBODY read JO 7400.11C for fun anymore?

https://www.faa.gov/regulations_pol...fm/go/document.information/documentID/1034252

If you really want to know the airspace boundaries, that’s the place to look. An example for one of the areas of the PHL Class B:

“Area A. That airspace extending upward from the surface to and including 7,000 feet MSL within an 8-mile radius of the Philadelphia International Airport (PHL), excluding that airspace bounded by a line beginning at the intersection of the PHL 8-mile radius and the 002° bearing from PHL, thence direct to lat. 39°56'14'' N., long. 75°12'11'' W., thence direct to lat. 39°55'40'' N., long. 75°08'31'' W., thence direct to the intersection of the PHL 8-mile radius and the 061° bearing from PHL, and that airspace within and underlying Areas B and C hereinafter described.”

Granted, not all of them are quite so complicated, especially Class D’s:

AGL MI D Saginaw, MI
MBS International Airport, MI
(lat. 43°31'59'' N., long. 84°04'47'' W.)
That airspace extending upward from the surface to and including 3,200 feet MSL within a 4.8- mile radius of MBS International Airport.

Enjoy some light reading!
Click to expand...
Thanks @RussR for actually trying to answer the question!

For everyone else, I didn't stick a wing or any other part of my airplane on any part of any line without permission. I'm just asking a technical question about the charts. Out of curiosity. No NASA form required.
 
eman1200 said:
I was just messin around, Russ. besides, I don't speak lat/lon.
Click to expand...

Yeah, I gotcha! But actually, it's a reasonable question. Circling areas, for example, are measured from the ends of each runway, not the center point of the airport.
 
This is one thing to take into consideration. The maps on ATC radar may be off by as much as a mile. This is probably the best reason to make sure you're well clear of any positive control airspace. They would show you violating it when what you have shows you are clear. Since most ATC radars are taped and if you are violated who do you think the FAA is going to believe?
 
You must log in or register to reply here.
Back
Top