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#1
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Newbie VOR question
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. |
#2
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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... |
#3
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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. |
#4
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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 |
#5
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"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 |
#6
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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). |
#7
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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 |
#8
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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." |
#9
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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. |
#10
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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. |
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