VOR and reverse sensing

"Robert Perkins" wrote in message
...
On Sat, 16 Aug 2003 01:04:26 GMT, "Dan Moos"
wrote:

Some one please give me an "Amen!" if they feel as I do

Most of the VOR terminology mentioned in this thread is correct, but that
doesn't make it useful for a beginner.

You can't have one from me.

Learn and use a VOR the way it was designed: as an instrument which
tells you your *position*, *not* your course line, and you'll never
have a problem with reverse sensing.


Yes, and no. First of all, my method doesn't disagree with what you say.
Nothing I wrote suggests that I know which way the plane is pointing by
looking at a snapshot of the CDI needle. Because it doesn't.

BUT, if I have 300 degrees dialed in to the OBS and keep the needle centered
for a few minutes or more, I think the VOR is great for giving you a course
line. Thats why it is the primary instrument for IFR navigation. Of course,
you need to use other instruments to establish yourself on that course line,
and until you do, it is true that the VOR only gives you your position. And
as far as describing your position to someonelse (ATC maybe), your method
is much more proper. That is why when ATC says "Hold southeast of HUH on the
120 degree radial", it makes sense.

If you do it that way, you're not perceiving radials, you're
perceiving lines.

Precisely. Most people understand lines, whereas radials require some
simplification. Really the only difference in doing it my way is that I
don't have to deal with reciprical values. I get the same results as your
method. I have NEVER misinterpreted a VOR reading, and personally think it
is the way of describing radials that is is taght in most places that is
responsible for confusing people about a simple instrument.

If you want to follow an arrow to your course, use
an ADF. VOR's are better for position detection.


My method works equally on ADF. I just think of an ADF as a VOR that
requires me to read my compass or DG to get what I need. You CAN follows
"radials" on an ADF this way, and my imaginary line through the NDB method
is especialy usefull here because there is enough calculation going on in
your head to follow a specific course line with the ADF that you don't need
weird reciprical course values to muddle things up.

Actually, I think a VOR is a FAR superior course following instrument then
an ADF. Look at it this way. I'm enroute IFR to the IAF. Lets first suggest
that the IAF in this case is an NDB. I'm enroute, and I lose my directional
gyro. lets also say that turbulence isa makeing the mag compass unreadable.
At this point I have no concrete idea What my course line is. What is the
wind doing? Who knows, because to use the ADF for COURSE information, I need
to also know my actual heading. No DG or compass, and the wind could
eventually make my track WAY of line. And if I'm aproaching the IAF, I'll be
maybe 1000 feet or less above pattern altitude when I get there, not good if
I have no real idea from which direction I'm approaching the station.

Do the same exercise whith the VOR. No problem, because the VOR is giving
you constant COURSE information. If the wind screws with you, you will see
it.

Here lies the main problem. If you truly believe that the VOR gives you no
course line info, then your way of thinking has caused you to not really
understand the instrument.

Learn and use a VOR the way it was designed: as an instrument which
tells you your *position*, *not* your course line, and you'll never
have a problem with reverse sensing.

No, with one exception, it does not tell you your position. That single
exception is when you overfly the antenna. Then, you may presume the antenna
is some altitude dependent radius from the nadir. Otherwise, the only thing
the VOR will tell you is BEARING from the station.

"Casey Wilson" wrote:
Learn and use a VOR the way it was designed: as an instrument
which
tells you your *position*, *not* your course line, and you'll
never
have a problem with reverse sensing.

No, with one exception, it does not tell you your position.
That single
exception is when you overfly the antenna.

No. One may use a VOR receiver and CDI to compute one's position by
flying perpendicular to a radial, timing the observed deflection, and
applying a simple formula.
--
Dan
C172RG at BFM

"Dan Luke" wrote in message
...
"Casey Wilson" wrote:
Learn and use a VOR the way it was designed: as an instrument
which
tells you your *position*, *not* your course line, and you'll
never
have a problem with reverse sensing.

No, with one exception, it does not tell you your position.
That single
exception is when you overfly the antenna.

No. One may use a VOR receiver and CDI to compute one's position by
flying perpendicular to a radial, timing the observed deflection, and
applying a simple formula.

In which case the VOR did NOT give you your position. The calculation
required additional instruments: A timer and some device (compass or DG) to
fly perpendicular to a radial, not to mention the use of the ASI, and so
forth. I say again, the VOR did NOT give you your position. By the way,
flying perpendicular to one radial is NOT perpendicular to the next, so the
calculation is flawed.

"Casey Wilson" wrote:
In which case the VOR did NOT give you your position. The
calculation
required additional instruments: A timer and some device (compass
or DG) to
fly perpendicular to a radial, not to mention the use of the ASI,
and so
forth.

Silly hair splitting. You also said the VOR will give you bearing from
the station: how will it do that without the use of other equipment?
--
Dan
C172RG at BFM

Student here, following debate with interest but I don't understand the
issue at disagreement. Considering "bearing" as distinct from "relative
bearing", is not the bearing the clockwise angular direction with respect
to the meridian over its origin of a line drawn from one point to another?
And since the 0 radial of the VOR station is aligned to the magnetic
meridian, each VOR radial indicates directly the magnetic bearing from the
VOR station to an object that lies somewhere along it. To get one's bearing
from the VOR station, than, can you not just rotate the OBS until the needle
is centred? If the "from" flag is up then the OBS ring reads out directly
the magnetic bearing to the aircraft as viewed from the VOR station, and if
the "to" flag is up, the OBS is showing the reciprocal. So don't you know
you're somewhere along that line? Of course, neither indication gives the
actual aircraft position without using some other additional means to
establish distance from the station - DME, triangulation on another station,
etc. Same principle with a movable card ADF set to or slaved to one's
compass heading, except that its needle is always indicating the bearing to
whatever station that's tuned so one needs to convert that reading into the
radial bearing from the station of interest to the plane (I know that the
conversion assumes the magnetic variation at the plane's position is not
different from that at the station's position, if you want to get precise).

"Dan Luke" wrote in message
...
"Casey Wilson" wrote:
In which case the VOR did NOT give you your position. The
calculation
required additional instruments: A timer and some device (compass
or DG) to
fly perpendicular to a radial, not to mention the use of the ASI,
and so
forth.

Silly hair splitting. You also said the VOR will give you bearing from
the station: how will it do that without the use of other equipment?


--
Dan
C172RG at BFM

"Steve House" wrote in message
...
Student here, following debate with interest but I don't understand the
issue at disagreement. Considering "bearing" as distinct from "relative
bearing", is not the bearing the clockwise angular direction with respect
to the meridian over its origin of a line drawn from one point to another?
And since the 0 radial of the VOR station is aligned to the magnetic
meridian, each VOR radial indicates directly the magnetic bearing from the
VOR station to an object that lies somewhere along it. To get one's
bearing
from the VOR station, than, can you not just rotate the OBS until the
needle
is centred? If the "from" flag is up then the OBS ring reads out directly
the magnetic bearing to the aircraft as viewed from the VOR station, and
if
the "to" flag is up, the OBS is showing the reciprocal. So don't you know
you're somewhere along that line?

Yes. That was my point exactly. Only, somewhere along that line could
be anywhere within about a 200 square mile area when you factor in the
inherent accuracy of the single VOR.

Of course, neither indication gives the
actual aircraft position without using some other additional means to
establish distance from the station - DME, triangulation on another
station,
etc.

Yes. That was my point exactly.

"Casey Wilson" wrote in message
...
No, with one exception, it does not tell you your position. That
single
exception is when you overfly the antenna. Then, you may presume the
antenna
is some altitude dependent radius from the nadir. Otherwise, the only
thing
the VOR will tell you is BEARING from the station.

How is that not "position"? Granted, it's not a very accurate description
of one's position, but it certainly describes one's position to an extent.

Given that the word "position" is simply being used to contrast with
heading, course, and other related terms, your objection seems pretty silly
to me.

Pete

"Peter Duniho" wrote in message
...
"Casey Wilson" wrote in message
...
No, with one exception, it does not tell you your position. That
single
exception is when you overfly the antenna. Then, you may presume the
antenna
is some altitude dependent radius from the nadir. Otherwise, the only
thing
the VOR will tell you is BEARING from the station.

How is that not "position"? Granted, it's not a very accurate description
of one's position, but it certainly describes one's position to an extent.

Given that the word "position" is simply being used to contrast with
heading, course, and other related terms, your objection seems pretty
silly
to me.

Who is being silly? You are relating apples and oranges. Bearing is
related to heading and course, position is related to geographical
coordinates. A single VOR won't tell you squat about geographical
coordinates.
Given that the "standard service volume" (AIM 1-1-8) is at least 40
nautical miles, the definition is not a trivial thing. I have tuned into VOR
stations as much as 85 miles away. So, where am I on that line from the
station.
Let's consider that the acceptable angular error [ FAR 91.171(b)(3) ]
can be plus/minus 6 degrees. I don't have my calculator, but I think the
formula is cosine of the angle times the distance... I'm only guessing, but
I think that at the forty mile limit, the aircraft could be as much as five
to seven miles on either side of the displayed bearing angle. Hmm, let's
see: base times height divided by two [40 miles times 5 miles then divide by
2] gives 100 square miles. Wait, that was only the half-angle -- multiply
by two to cover the other side and we are up to 200 square miles of area
over which the airplane could be flying.
I like using the VOR, I like having two of them in the panel. Hell, I
even like the ADF -- got one of those too. When I triangulate any two of
those, I have a rough idea of my 'position.'

"Casey Wilson" wrote in message
...
Who is being silly? You are relating apples and oranges. Bearing is
related to heading and course, position is related to geographical
coordinates. A single VOR won't tell you squat about geographical
coordinates.

I have no idea what you're talking about.

Bearing relative to the VOR station is all about your position relative to
the station. Knowing your bearing relative to the station greatly narrows
down your geographical coordinates. You can get a lot more accurate using a
second VOR or DME, but that doesn't change the fact that even a single VOR
is telling you a lot about your geographical coordinates.

While on the other hand, the bearing relative to the VOR has NOTHING to do
with heading or course. Nothing at all. It boggles my mind that you would
say it does. The mistaken impression that it does have something to do with
heading or course is where lots of people (the original poster included) get
confused. You're just making matters worse by saying that it does.

Given that the "standard service volume" (AIM 1-1-8) is at least 40
nautical miles, the definition is not a trivial thing. I have tuned into
VOR
stations as much as 85 miles away. So, where am I on that line from the
station.

Just knowing you're on that line is useful GEOGRAPHICAL POSITION
information.

[...] and we are up to 200 square miles of area
over which the airplane could be flying.

All you're doing is bickering about just how accurate the GEOGRAPHICAL
POSITION information is. A single VOR isn't very accurate at all. Two VORs
are more accurate. A VOR with DME is even more accurate. Two VORs with DME
each are even more accurate. And a GPS receiver is even more accurate. So
what? They all still give you geographical positions.

I like using the VOR, I like having two of them in the panel. Hell, I
even like the ADF -- got one of those too. When I triangulate any two of
those, I have a rough idea of my 'position.'

No triangulation is needed to get a rough idea of your position.
Triangulation reduces the "roughness" of your position estimate, but a
single VOR receiver alone gives you a rough idea of your position. (An ADF,
of course, does no such thing...it MUST be referenced to another instrument
to provide ANY positional information at all).

Pete