First, "degrees" and "radials" are two different things and the words are not used interchangeably. That is, the word degrees is not used in describing a radial.
I did not use "degrees" and "radials" interchangeably (that is, to mean the same thing). I didn't even use "degrees." And your "the word degrees is not used in describing a radial" is not even remotely the same as your "that" (saying the words aren't used interchangeably). Besides this, the statement is wrong. Watch this:
A "radial" (in the aeronautical sense) is a direction or "line of direction" from a radio navigational transmitter, with the direction specified in degrees of angle from the direction of the magnetic north pole from the same transmitter.
You see. The word "degrees" is used in describing a radial. I just did it. There is probably no way of describing a "radial" to someone not already steeped in aviation so that the person understands without using the word "degrees."
I think that your concern must be about my "175° radial," which when spelled out without a symbol would be "175-degree radial." I expect that flyers sitting in the cafe near the airport don't say the "degree" or "degrees" and that it's left out of aviation comms just to minimize words. All those av people understand without the "degree" or "degrees." But the intent of my post was to try to communicate to english-language-reading people with various backgrounds. I probably wouldn't be very good at writing in aviation jargon even if I wanted to. You'll have to do the translating for yourself.
The 1971 Portland chart has been duplicated so much that it is difficult to read.
I can't imagine which chart you mean, or what the point is. I don't have any difficulty reading the chart I posted. I assume you're referring to generations of copies. Copies of copies of copies, etc.
The dashed line marking an area around the Portland airport also has a specific meaning. Fortunately, the FAA publishes an excellent booklet which describes the present day meaning of everything on their charts. Just go to the faa.gov web page and search the publications until you find it. You can download it free and it should answer all of your questions.
Won't work, Robert. What we need is not "present day meaning." We're looking at older charts. All that matters is what the '71 sectional said. I have a fairly current 1 for IFR chart symbols and one for VFR. Thanks.
But in looking at the 1971 Portland chart, it appears that the only "control area" there is the "airport traffic control area", which was not printed on charts in that day, which has a specified diameter (I don't remember exactly but it was probably 10 statute miles) and a ceiling of 3000 feet above the airport elevation.
Yet, the area is on the piece of 1971 sectional I posted, marked with the long dashes, short spaces. It's not totally circular. I've attached a piece of a legend from a '71 L-1. It shows that symbology as meaning "control zone" in 1971. On the actual '71 L-1 chart the same outline as on the "FBI" plot is marked by the "T" fence for which the legend says "
Control Zones within which fixed-wing
special VFR flight is prohibited."
(emphasis added)From Wikipedia, not that they're experts:
"A control zone (CTR or Controlled Traffic Region) in aviation is a volume of controlled airspace, normally around an airport, which extends from the surface to a specified upper limit, established to protect air traffic operating to and from that airport. Because CTRs are, by definition, controlled airspace, aircraft can only fly in it after receiving a specific clearance from air traffic control. This means that ATC at the airport know exactly which aircraft are in that airspace, and can take steps to ensure aircraft are aware of each other, either using separation or by passing traffic information.
"In the USA the term control zone is no longer used and has been replaced by airspace class D.
Typically it extends 5 miles in diameter with a height of 2500 ft AGL (above ground level) around small commercial airports. Aircraft are required to establish radio contact with the control tower before entering and to maintain in contact while in class D airspace. This implies that an aircraft must be equipped with at least a portable radio to fly in Class D airspace."
I have seen that the long dash, short space thing is identified as "class D" on newer charts (like wiki sorta says). The way they put it, there could be some deviations on the radius and height.
The magenta colored area is not a control area. Rather, it specifies a visibility (in miles) and altitude (above ground level) below which VFR flight is permitted.
I think you're referring to an area outlined with a magenta band on newer charts? On the one I attached, it looks like a dim red band inside a dim blue band. Apx 39nm dia on the chart? Extends down to apx Oregon City, Lenhardt & Newberg?
But the biggest question here is, why would the airliner fly such a convoluted path around Portland when a simple straight line on the west side of Portland would be the simplest and best? Keep in mind that the airliner did not know until it was in the Portland area that it would probably be able to make it non-stop to Reno. The NWA performance engineers in Minneapolis passed the crew that information through the ARINC system. Passing Portland on the east side would have added another 10 to 15 miles to their distance. Also, the aircraft was difficult to fly including turns and changes in altitude.
They were focused on getting the guy out without the guy exploding a bomb. I can imagine that they had to work at focusing hard just to function in the midst of the fear. Getting him to leave was probably
all they cared about. It would be easy (mentally) just to fly where they had been cleared to fly. V23 Easy just to watch the deviation and the compass. If they had found that they wouldn't be able to make Reno because of 15 miles, they would have just had to try to convince the guy that they really did need to go to an alternate they had already established.