Newbie VOR question

[Bruce W.1]

I'm not a pilot but I have been reading up on VOR stations. And I'm
looking for practical information.

You can calculate your position by triangulating from two VOR stations.
How many pilots do this? Or do most just fly between omnis? When you
fly cross country do you just fly VOR to VOR, or do you draw a straight
line to your destination and constantly triangulate while enroute to see
if you are on this line?

Is it practical to fly a straight line course? Anybody do this?

Thanks for your help.

[Grumman-581]

In other words, you're trying to figure out how to navigate in MS Flight
Simulator...

VOR triangulation is learned and practiced during your initial PPL
training... Some people use it afterwards, some rely on GPS or LORAN... Once
you learn it, it's simple enough that you're not likely to forget it, so
some (perhaps many) pilots don't practice it anymore...

VFR flights are traditionally flown straight to destination using dead
reckoning and pilotage (i.e. point it in the right direction and look for
landmarks along the way)... IFR flights have tranditionally been flown VOR
to VOR... These days with IFR certified GPSs, things have probably
changed...

Flying cross country might be a direct flight if there are no airspaces that
you need to avoid...

Oh well, so much for the nickel tour...

[Jose]

> You can calculate your position by triangulating from two
> VOR stations. How many pilots do this? [...]

17,328, as of March 31.

Just kidding.

The intersections of two VORs are used for position in several ways...
one of them is finding ones position when lost. It's not much of a
"calculation" - it involves trying to draw two lines on the chart that's
half folded in your lap while flying an airplane, usually as the ceiling
is dropping, it's getting dark, and you have to go to the bathroom
really badly. A little turbulence doesn't help either. Once you find
where those lines intersect, you look down and see if you can recognize
anything that resembles what's on the map at that intersection point.
The number of pilots who have done this is pretty close to the number of
pilots that have ever gotten lost in visual conditions. This is
probably pretty close to the number of pilots.

A more common use of this triangulating technique is when flying
directly towards or away from one of the VORs; one can use the other VOR
to monitor one's position along the intended flight path. This is one
of the techniques used on an instrument approach to determine when one
is past a certain point (and thus able to descend further without
hitting anything). Every IFR(*) pilot has done this. However on an
instrument approach the intersections are predetermined on paper, and
one merely needs to know "is it soup yet?". You set the other VOR to
the desired intersecting radial, and wait for the needle to center.

The same is true when flying cross country under IFR. Very often one is
flying directly towards or away from a VOR, and intersections are used
to keep track of one's progress. Outside of a radar environment, they
are also used to report one's position to ATC, so they know when to let
other airplanes use the airspace you were just in. Sometimes one flies
to an intersection and then changes course to fly towards (or away from)
the other station. The technique is similar to that on an approach -
set the other VOR to the desired intersecting radial, and when the
needle centers, you're there.

RNAV (which can be based on VOR, DME, and/or GPS) has made it
unnecessary to actually fly directly to or from VORs - the computer
inside continuously calculates one's position based on whatever
navigation signals are being used. However air traffic control will
often require a pilot to fly the airway to keep things simple enough to
keep track of on the ground. It's easier (and safer) even in a mostly
empty parking lot to drive the lanes rather than cut across the parking
rows, especially if other people are also driving around.

When I fly VFR cross country (which means I can decide my route on my
own, without any input from ATC), I like to fly in a straight line, low,
and using pilotage (using landmarks) for navigation, so I don't pay much
attention to VORs. The practicality of a straight line course depends
on factors such as restricted airspace, terrain, and altitude. Slight
bends in the route don't add much to the flight, especially if they are
planned for (so the angular deviation is small). Note that a "straight
line" curves because the earth is round, and in most cases the compass
heading will be changing as you fly. This is an issue only over long
flights (say, several hundred miles). You can actually see this by
opening up a sectional (the VFR charts pilots use) and drawing a
straight line East to West across the entire length of the map. Compare
that line with the lines of longitude.

Flying IFR cross country, especially at the lower altitudes, I file and
fly the airways (which are generally to or from VORs) because the
minimum altitudes have been set out for me on the charts. Off the
airways, I'd have to fly higher to ensure terrain clearance, and that
might not be practical due to icing, or I might want certain altitudes
for other reasons (it's pretty to fly in and out of cloud). I monitor
my progress by tuning the other VOR to the intersections on the charts,
and watching the needle indicate their passage. At least until we got
the GPS. Now I watch the purple line, and back it up with VOR navigation.

Hope this helps. :)

(*)
IFR: instrument flight rules - the set of rules one flies by to avoid
bending aluminum when flying in IMC
IMC: instrument meteorological conditions - weather conditions that
requires one to depend on instruments to keep the dirty side down, and
requires one to depend on air traffic controllers to keep aluminum away
from you.
VFR: Visual flight rules - the set of rules used in VMC. Under VFR,
the pilot is responsible for avoiding hitting other airplanes. He or
she does so by looking out the window. And taking evasive action when
necessary.
VMC: Visual meteorological conditions - weather good enough to "see and
avoid" hitting aluminum, fiberglass, and granite.

Jose
--
Get high on gasoline: fly an airplane.
for Email, make the obvious change in the address.

[Don Tuite]

On Mon, 04 Apr 2005 02:58:18 GMT, "Bruce W.1" > wrote:

>I'm not a pilot but I have been reading up on VOR stations. And I'm
>looking for practical information.
>
>You can calculate your position by triangulating from two VOR stations.
> How many pilots do this? Or do most just fly between omnis? When you
>fly cross country do you just fly VOR to VOR, or do you draw a straight
>line to your destination and constantly triangulate while enroute to see
>if you are on this line?
>
>Is it practical to fly a straight line course? Anybody do this?

GPS has changed things. VFR, before GPS, you'd tend to look out the
window to see where you were, relative to that line you'd drawn on
your chart. Triangulation was mostly for when you'd been daydreaming
and looking out the window wasn't much help because one meandering
river looks like another meandering river.

I should say that I may have been spoiled by doing most of my flying
in the parts of the US West where landmarks are many and conspicuous.
But even on the Great Plains, I think VFR pilots would still plot a
rhumbline course. You'd have to be damned careful about following the
compass, but given that, the first thing you'd do is use landmarks or
the intersection of your course with a few VOR radials and landmarks
to work out your actual drift angle. Then you'd point your nose so as
to cancel out the drift and keep refining that.

I don't know what pilots do on the East Coast. The only time's I've
flown there, I could see for miles. But I hear that's rare.

But generally, making continually sure that what you see out the
window looks like what's on your chart is best. The worst thing, VFR,
is keeping your eyes on those round things on the panel all the time.

Don

[Happy Dog]

"Bruce W.1" > wrote in message

> I'm not a pilot but I have been reading up on VOR stations. And I'm
> looking for practical information.
>
> You can calculate your position by triangulating from two VOR stations.

Well, just calculating an intersection. Thhere's always a question or two
about this on PPL and CPL exams.

> How many pilots do this? Or do most just fly between omnis? When you
> fly cross country do you just fly VOR to VOR, or do you draw a straight
> line to your destination and constantly triangulate while enroute to see
> if you are on this line?

Very few. A 20.00 GPS is more accurate. Get two, JIC.
>
> Is it practical to fly a straight line course? Anybody do this?

VFR? Sure. IFR? With GPS, more and more.

moo

[Bruce W.1]

Don Tuite wrote:
>
>
> GPS has changed things. VFR, before GPS, you'd tend to look out the
> window to see where you were, relative to that line you'd drawn on
> your chart. Triangulation was mostly for when you'd been daydreaming
> and looking out the window wasn't much help because one meandering
> river looks like another meandering river.
>
> I should say that I may have been spoiled by doing most of my flying
> in the parts of the US West where landmarks are many and conspicuous.
> But even on the Great Plains, I think VFR pilots would still plot a
> rhumbline course. You'd have to be damned careful about following the
> compass, but given that, the first thing you'd do is use landmarks or
> the intersection of your course with a few VOR radials and landmarks
> to work out your actual drift angle. Then you'd point your nose so as
> to cancel out the drift and keep refining that.
>
> I don't know what pilots do on the East Coast. The only time's I've
> flown there, I could see for miles. But I hear that's rare.
>
> But generally, making continually sure that what you see out the
> window looks like what's on your chart is best. The worst thing, VFR,
> is keeping your eyes on those round things on the panel all the time.
>
> Don
>
================================================

GPS takes most of the challenge out of navigation, and the fun too,
depending on your perspective. In rough IFR weather to hell with the
challenge.

I used to fly with my Dad, a weekend warrior pilot, but never paid much
attention to the navigation.

If I had my way I'd have a drafting table setup in the back of the plane
(with charts all over the place) and be navigating with a sextant.

It sounds like you guys that still use VOR's fly to/from them and maybe
make course corrections when you hit a radial from another VOR. Just
seems like a zig-zag way to get around, but the easiest way (without GPS).

[Paul Tomblin]

In a previous article, "Bruce W.1" > said:
>It sounds like you guys that still use VOR's fly to/from them and maybe
>make course corrections when you hit a radial from another VOR. Just
>seems like a zig-zag way to get around, but the easiest way (without GPS).

Some people have rho-theta RNAV systems which to the calculations for you,
so you can say "I want to fly to a point that's 23DME on the 186 radial
from that VOR", and it will give you a CDI just as if you were flying
directly to the VOR.

The plane that I flew up here to where I'm currently weathered in has a
KNS-80 that can supposedly do that, but I've never found the need. In IFR
you pretty much are on the airways or going direct to a VOR, and in VFR I
just use the GPS and go direct to the destination.

--
Paul Tomblin > http://xcski.com/blogs/pt/
I've never understood why women douse themselves with things that are alleged
to smell of roses/tulips/freesias. What exactly are they trying to attract?
Bees? -- Tanuki

[William W. Plummer]

Bruce W.1 wrote:

> Don Tuite wrote:
>
>>
>>
>> GPS has changed things. VFR, before GPS, you'd tend to look out the
>> window to see where you were, relative to that line you'd drawn on
>> your chart. Triangulation was mostly for when you'd been daydreaming
>> and looking out the window wasn't much help because one meandering
>> river looks like another meandering river.
>>
>> I should say that I may have been spoiled by doing most of my flying
>> in the parts of the US West where landmarks are many and conspicuous.
>> But even on the Great Plains, I think VFR pilots would still plot a
>> rhumbline course. You'd have to be damned careful about following the
>> compass, but given that, the first thing you'd do is use landmarks or
>> the intersection of your course with a few VOR radials and landmarks
>> to work out your actual drift angle. Then you'd point your nose so as
>> to cancel out the drift and keep refining that.
>> I don't know what pilots do on the East Coast. The only time's I've
>> flown there, I could see for miles. But I hear that's rare.
>>
>> But generally, making continually sure that what you see out the
>> window looks like what's on your chart is best. The worst thing, VFR,
>> is keeping your eyes on those round things on the panel all the time.
>>
>> Don
>>
> ================================================
>
> GPS takes most of the challenge out of navigation, and the fun too,
> depending on your perspective. In rough IFR weather to hell with the
> challenge.
>
> I used to fly with my Dad, a weekend warrior pilot, but never paid much
> attention to the navigation.
>
> If I had my way I'd have a drafting table setup in the back of the plane
> (with charts all over the place) and be navigating with a sextant.
>
> It sounds like you guys that still use VOR's fly to/from them and maybe
> make course corrections when you hit a radial from another VOR. Just
> seems like a zig-zag way to get around, but the easiest way (without GPS).

Several years ago I was taking a tour of a C-130 at a USAF air show.
In the flightdeck, I looked around and asked the pilot, "What. No
GPS?". He looked at me and snorted, "No. We work for a living."

[Larry Dighera]

On Mon, 04 Apr 2005 05:59:41 GMT, "Bruce W.1" > wrote in
>::

>It sounds like you guys that still use VOR's fly to/from them and maybe
>make course corrections when you hit a radial from another VOR. Just
>seems like a zig-zag way to get around, but the easiest way (without GPS).

You'd be surprised at how little the distance increases on a VOR route
compared to a direct route.

[Paul kgyy]

If you purchase an aviation map (Sectional Chart) it will show airways
based on flying from VOR to VOR, and many pilots still use these for
navigation even when GPS is on board. In my Instrument Proficiency
Checkride last week, the instructor asked me after practicing a bunch
of maneuvers to use triangulation to figure out without looking out the
window where we were. When I showed him the general area we were
located, he asked me to fly to one of the VORs using the 260 degree
radial. This required flying north until the needle centered, then
turning to 260 degrees.

[Bruce W.1]

Larry Dighera wrote:
>
> You'd be surprised at how little the distance increases on a VOR route
> compared to a direct route.
>
>
================================================

You're probably right about the distance. But doesn't everbody flying
TO/FROM VOR stations cause air traffic problems like near misses
(collisions)? Or being aware of this do you just watch the skies very
carefully near VOR stations? Or are there altitude guidelines for each
radial?

[Dan Luke]

"Bruce W.1" wrote:
> But doesn't everbody flying
> TO/FROM VOR stations cause air traffic problems like near misses
> (collisions)? Or being aware of this do you just watch the skies very
> carefully near VOR stations? Or are there altitude guidelines for each
> radial?

Sort of. There are rules defining what the usable altitudes are based on
magnetic course being flown. Opposite direction traffic should be at least
500' apart, vertically. This offers no protection, though, for aircraft
flying in the same direction or on converging courses that are on the same
side of the compass.

http://www.faa.gov/ATPUBS/AIM/Chap3/aim0301.html#3-1-5 defines VFR cruising
altitudes, which are 1,000' apart. IFR altitudes are 1,000' apart, too, but
are 500' above or below VFR altitudes. Above FL290 the IFR cruising
altitudes are 2,000' apart.
--
Dan
C-172RG at BFM

[Don Tuite]

On Mon, 04 Apr 2005 18:58:38 GMT, "Bruce W.1" > wrote:


>You're probably right about the distance. But doesn't everbody flying
>TO/FROM VOR stations cause air traffic problems like near misses
>(collisions)? Or being aware of this do you just watch the skies very
>carefully near VOR stations? Or are there altitude guidelines for each
>radial?

Traffic may be heavier over VORs, and the closer your heading is to
due North or South (where the hemisphere[1] rule toggles, the more
alert you should be.

That said, I've never actually noticed a particularly heavy increase
in traffic over VORs.

Don
[1] Why hemiSPHERE? Semi-circle I could see, but . . . .

[George Patterson]

Bruce W.1 wrote:
>
> You can calculate your position by triangulating from two VOR stations.
> How many pilots do this? Or do most just fly between omnis? When you
> fly cross country do you just fly VOR to VOR, or do you draw a straight
> line to your destination and constantly triangulate while enroute to see
> if you are on this line?

When I navigate using the VOR network, I usually go VOR to VOR in congested
airspace and straight line for long cross-countries. When traveling straight
line, I frequently use the triangulation method to verify my location when there
are no good landmarks nearby. I frequently use triangulation to determine the
point at which I pass an intersection or waypoint (whether official or
otherwise). For example, I may fly one radial from VOR "A" to remain outside the
DC ADIZ, but I know that I can change course once I pass the point at which a
particular radial of a second VOR crosses that one. In any case, I treat the VOR
network as sort of a backup to pilotage (and I treat pilotage as a backup to
LORAN/GPS).

As Larry pointed out, in most cases, using the airways usually doesn't increase
your enroute time all that much over going direct.

George Patterson
Whosoever bloweth not his own horn, the same shall remain unblown.

[Larry Dighera]

On Mon, 04 Apr 2005 18:58:38 GMT, "Bruce W.1" > wrote in
>::

>Larry Dighera wrote:
>>
>> You'd be surprised at how little the distance increases on a VOR route
>> compared to a direct route.
>>
>>
>================================================
>
>You're probably right about the distance. But doesn't everbody flying
>TO/FROM VOR stations cause air traffic problems like near misses
>(collisions)?

Congested airways near VORs can be an issue. But the designers of the
VOR airway system had enough insight to separate east and west bound
VFR traffic by 1,000' vertically, and IFR traffic from VFR traffic by
500'. But airways, being only 4 nautical miles wide either side of
centerline can be congested over VORs.

>Or being aware of this do you just watch the skies very
>carefully near VOR stations?

Yes. That and ATC Radar Advisory Service are the principal methods
used to separate VFR flights on VFR airways.

>Or are there altitude guidelines for each radial?

Nope.

Have you spent any time reviewing this:
http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgFAR.nsf/CurrentFARPart!OpenView

[Klein]

On Mon, 4 Apr 2005 13:03:03 +0000 (UTC),
(Paul Tomblin) wrote:

>In a previous article, "Bruce W.1" > said:
>>It sounds like you guys that still use VOR's fly to/from them and maybe
>>make course corrections when you hit a radial from another VOR. Just
>>seems like a zig-zag way to get around, but the easiest way (without GPS).
>
>Some people have rho-theta RNAV systems which to the calculations for you,
>so you can say "I want to fly to a point that's 23DME on the 186 radial
>from that VOR", and it will give you a CDI just as if you were flying
>directly to the VOR.
>
>The plane that I flew up here to where I'm currently weathered in has a
>KNS-80 that can supposedly do that, but I've never found the need. In IFR
>you pretty much are on the airways or going direct to a VOR, and in VFR I
>just use the GPS and go direct to the destination.

I used to fly a plane equipped with a KNS-80. The way I used it to
straighten out my course was to dial in the radial and distance to the
(n+1)th VOR in my flight plan as soon as I came in range of the nth
VOR in my plan. This also allows you to avoid overflying the VORs
with their higher traffic density. But give me GPS any day!

Klein