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David_FFC

VOR Inconsistencies - Long Post

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Does anyone know why not all VOR's are aligned with their 0 (zero) degree radial pointing to magnetic north ? I'm refering to the sectional charts. I've asked my CFI, another CFI, the Atlanta area FSDO (no response from them yet), one regional commercial pilot, and three other single-engine-land pilots, and none of them have an answer to this question. They all thought that all VOR's have their zero aimed at mag north. That's what we'll all been taught. But a quick look at a chart will tell a slightly different story. I never noticed this either during the last 5 years of using sectionals for simming, because I never corrected my courses for true/mag. But, one day a couple of weeks ago I had to plot a course to Columbus, GA, from FFC, and had to correct the true course for winds and mag deviation, and Columbus' VOR was just staring right at me, not jiving with the isogonic line right next to it. On our first cross country, the VOR's were not very close to a flight path, or else I would have seen this sooner.Examples of a few that are not quite right -- Columbus (CSG), LaGrange (LGC) and Macon (MCN), GA, Tuskegee (TGE), AL, and, Choo Choo (GQO - Chattanooga, TN). They all have zero aimed a little to the east of true north, from 1 to 2 degrees, while the isogonic lines in the last few years in the areas of these VOR's have been from 2W to 3W !!! That's a 3 to 4 degree difference, which isn't a whole lot, granted, and for IFR purposes, your aircraft's VOR can legally vary +/- 4 on the ground, and +/- 6 in the air. But still, that means if you start towards CSG on its 300 radial, say, about 60 miles away, if you fly on a 300 mag heading, you won't stay on, but you'll stray from, the 300 radial. You'll need to fly a 304 heading, or else you'll go to the south of the VOR.PP99 also apparently has at least the same VOR alignments for TGE and CSG, because I flew from TGE to CSG (no wind) on the 76 TO of the CSG radial, on a mag heading of 76, which eventually made me fly towards the north of the VOR center. I had to have a mag heading of, sure enough, around 80 degrees to stay on the 76 radial. Two VOR's in the surrounding area that appear to be better aligned with mag north : Spartanburg (SPA), SC, and Charlotte (CLT), NC -- at least they're pointing to the left (west) of true north. There are a host of others that are real close.And, there are others that aren't. I've looked at the Atlanta, St. Louis, Kansas City and Omaha sectionals. It's real easy to spot the ones that are off (without a plotter) in these areas because the real mag deviation from true north is only a couple of degrees, and it's real easy to eyeball the VOR's zero line with a longitude line. The Seattle area might not be so obvious.I realize it is obviously easier to change the position of the isogonic lines on the charts from one issue to the next, but not so easy to realign the VOR's across the country. But the first group of VOR's I've mentioned would have the North mag pole in the direction from GA towards Lake Huron and the East side of Hudson Bay (unknown pole location - just the general direction), instead of around 75 North Latitude, due North of North Dakota, where it's been, roughly, since at least 1963, although it does move a bit. In fact, I've read recently that the North mag pole's movement has been accelerating towards Siberia, taking it on a path between Alaska and the True North Pole.So, in summary, since the VOR's are not all aligned correctly, and haven't appeared to be for who knows how many years, I'm wondering when was the last time the VOR's were aligned, and why in the direction that is currently represented ?Call me "wondering" Dave H. inFayetteville, GA

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Your whole issue of VOR alignment may be a moot point soon. The goal is to make GPS the dominant navigation system in the future. Jerry K. ThorneEast Ridge, TN.

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>Your whole issue of VOR alignment may be a moot point soon. >The goal is to make GPS the dominant navigation system in >the future. >>Jerry K. Thorne >East Ridge, TN. Jerry, did you see this year's AVweb's AVfalsch ?Here's a relevant excerpt - could this piece of fiction actually come close to real life (the 2nd paragraph actually happening after the 1st)? Man, I hope not !(For those that don't know, www.avweb.com publishes a Mon and Thu aviation news summary called AVflash. For April 1, they call it AVfalsch ("falsch" is German for "false"), and some of the stories look pretty normal until you get a few lines into them.)****************************************************************ALL U.S. VORS TO BE DECOMMISSIONED THIS SUMMER...The FAA announced last week that it has decided to stop operating andmaintaining the nation's VOR navigation system. Citing extensive useof GPS by general aviation and INS/IRS by air carriers, the agency hasdecided to phase out the navaids five years earlier than previouslyannounced. "Nobody uses VORs anymore anyway," said Nora Fitzpatrick,FAA acting deputy associate administrator for navigation services.According to Fitzpatrick, TVORs are scheduled be switched off by May31, LVORs by July 31, and HVORs by August 31 (except in Alaska).Localizers will remain unaffected until WAAS becomes operational....WHILE TWO-DAY GPS OUTAGE PLANNED FOR AUGUSTIn a related story, the DOD notified the DOT last week that it wouldshut down the GPS satellite array August 1-3 to install upgrades insecurity software. The Pentagon says the new security software willhave the ability to determine which GPS receivers are being used forterrorist purposes and transmit bogus navigation signals to them. Anew FDC NOTAM cautions pilots to use alternate means of navigation tocross-check their GPS-derived positions during August.**********************************************************************Alright! One of my favorite words ! : "moot"Do you mean it in the non-legal, or legal sense, which are BTW quite different ? When someone says "that's a moot point", I'll often reply, "well, then, let's debate it since it is debatable", and they haven't a clue what I mean.adjective1. Subject to debate; arguable: a moot question.2. a. Law. Without legal significance, through having been previously decided or settled. b. Of no practical importance; irrelevant.Usage Note: As an adjective moot has come to be widely used to mean "no longer important, irrelevant," as in "It's a purely moot question which corporation you make your rent check out to; Brown will get the money in either case." This usage may be originally the result of a misinterpretation of its legal sense in phrases such as a moot question. A number of critics have objected to this use, but it was accepted by 59 percent of the Usage Panel in the sentence "The nominee himself chastised the White House for failing to do more to support him, but his concerns became moot when a number of Republicans announced that they, too, would oppose the nomination."FROM :The American Heritage Dictionary of the English Language, Third Edition is licensed from Houghton Mifflin Company. Copyright

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Dave,Did you notice that the date on that was April 1st? The five-year phase-out of VOR's is still the plan last I heard. The feds have been talking about offering to the public the same stuff they use to prevent jamming of GPS receivers. Without that little fix, GPS would not be reliable. I know, I flew through an area west of Orlando a year or so ago and the GPS I was using went dead until I got near to Ocala. The GPS went out while I was traversing that area in both directions that day.Jerry K. ThorneEast Ridge, TN.

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From www.airnav.com, for Columbus, GA Airport and NAVAID :(I've read the included caveat at the web site that states "This information may not be accurate or current", but the info which includes dates, matches what I know to be true on all the latest charts.)CSG - COLUMBUS METROPOLITAN AIRPORTCOLUMBUS, GAAIRPORT INFORMATION AS PUBLISHED ON 21 FEBRUARY 2002Location Lat/Long: 32-30-58.800N / 084-56-19.900W (32.5163333 / -84.9388611) (estimated) Elevation: 397 ft. / 121.0 m (surveyed) Variation: 02W (1990) 80.0 kts. We expect some deviation there. If a runway is marked 27, we should know that its real mag direction can be from 265 to 274, which is a total of 10 different degrees. But if someone says a VOR's zero radial is oriented to mag North, and we know a VOR has resolution to one degree, we kind of expect that to be more of an absolute.My whole point in this little exercise is to show that even though we're told that a VOR's zero radial is aligned with mag North, and is presented as though it is an absolute (as evidenced by many "experienced" people I've talked to that did not know there were these inconsistencies - I talked to another airline Captian today during lunch, and he didn't know this), the VOR's alignment may be many years old, which means it can be up to at most 4 degrees off (the most I've found to date) of the latest isogonic lines on the same chart.So, whether sim or real, unless you know about these little variation inconsistencies, don't be surprised when you are flying towards a VOR on a given TO radial, on the same numbered heading, that you may find yourself constantly correcting your heading by as much as 4 degrees to stay on your original radial. This is even AFTER you've corrected for wind, regardless of speed. Your course will look something like this :* * * * * * * * * * * * * * 300 HDG. A few minutes go by. Oops, I'm not on the 300 radial anymore; well, I'll wait a minute or so. Oops, off even more - turn to 302, no 304 -- not enough - maybe 306 to get back on ? Ok, back on - now back to 300 HDG. Don't know why I couldn't stay on the radial - can't be the wind - there isn't any. A few minutes go by. What, off the 300 radial again ? Well, turn to 302 ... etc. Ya know, I just better forget my intended HDG and fly straight to the VOR. But that's what I thought I was doing !! How do I know what the HDG should be ? It's certainly not 300 !!! More like 304 - my VOR instrument must be getting a little inaccurate - surely the real VOR wouldn't be that much off.* * * * * * * * * * * * * * You'll end up doing a lot of very small s-turns, weaving back and forth. Oh, well -- at least you'll stay awake.Just another one of the many fine points of aviation.Dave H.Fayetteville, GA

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>Dave, >>Did you notice that the date on that was April 1st? The >five-year phase-out of VOR's is still the plan last I heard. Yes, sir - that's why I mentioned that it was from the "AVfalsch" version (the April Fool's version). This year, because April 1 was also on a day they issue a "real" set of stories (Mon), one had to be careful which one was being read -- although the content of the "false" version gives it away -- like reopening Mueller in Austin: "Austin's demographic has changed a lot since Mueller closed in 1999," Austin's mayor said. "The dot-coms have folded and no one has any money for luxury lofts and jazz bars anymore, so we might as well let the pilots have the airport, and pick up some tax revenue somewhere."Oh, if only Austin's mayor and city council and land developers could be so reasonable.> The feds have been talking about offering to the public the >same stuff they use to prevent jamming of GPS receivers. >Without that little fix, GPS would not be reliable. I know, >I flew through an area west of Orlando a year or so ago and >the GPS I was using went dead until I got near to Ocala. >The GPS went out while I was traversing that area in both >directions that day. Yikes ! Not very comforting for those IFR pilots! I still like the NDB's - kinda like having a plethora of little magnetic poles.Dave H.Fayetteville, GA

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Now I am getting scared, Dave. I had such faith in the F.A.A. And now you bring up this whole can of worms. No more VOR for me; it's ded. reckoning from now on. But, don't the commercial airliners use VOR? Oh well, pull out the train schedule - let's see, Santo Domingo to New York on Amtrak. At least the rails never vary from their destination.Best regards.Luis

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>>>And now you bring up this whole can of worms. But, don't the commercial airliners use VOR? Oh well, pull out the train schedule - let's see, Santo Domingo to New York on Amtrak. At least the rails never vary from their destination. >>Best regards. >>Luis Yeah, I'm real good at worm bringing-up. Can we say "over-analyze?"I prefer to think of it as "adequately" analyze.But, I've been burned so many times by not delving further into a subject. When I see something a little out of kilter, a little red flag always seems to go up when I ask someone to explain it, and they say, "oh, that's not inmportant", or "I'm not sure why", or I get an explanation where I get a feeling I'm not getting the whole story. And almost always, just like Paul Harvey, I discover there really is a "rest of the story."The Airlines use VOR's somewhat, but rely heavily on GPS, as indicated by Uncle Sam wanting to remove the VOR's in 5 years, and by the improvement of the accuracy of the GPS's about a year ago (actually, the accuracy was already there - the US simply removed a "restriction" of the signal). This is what scares "me" ! What if something happens to the satellites ? Either by a terrorist thing, or unusually large "bad" solar activity, or a few stray meteors. They'd only rip through the satellite at 25,000 mph or so - nothing real bad.I'm kinda like you - give me dead reckoning, plus an NDB, and the stars at night, and I'll be fine.Amtrak from Santo Domingo to NY ! Maybe it could go underwater like a Disney ride ? Sounds pretty cool, Luis ! Guess we can take up a collection right now, eh ?Call me "Analyze it 'til it squeals" Dave, fromFayetteville, GA

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Luis, strange you should mention Amtrak :(APR 18)CRESCENT CITY, Fla. (AP) - An Amtrak train en route from suburban Orlando to theWashington, D.C.-area derailed Thursday. There were no immediate word of deaths or injuries. Television reports said at least 17 cars on the Autotrain derailed shortly after it left Sanford. Video from television helicopters showed passengers climbing on the sides of the cars. The train carries automobiles and passengers between the Orlando area and Virginia. Crescent City is 61 miles north of Orlando.Like they say, the only thing you can depend on is death and taxes.(And there's gotta be a couple of other things, but not many).Dave H.Fayetteville, GA

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Thanks, Dave. You really know how to make a guy feel better.Scratch the Amtrak - I am staying home this weekend.Luisnot scared, just prudent

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You forgot to mention inertial navigation. That is actually used more on the airlines than GPS. The new CRJ commuter jets come standard with GPS in the panel. GPS is not standard equipment on most Delta Airlines jets.I am off to Portugal again on Saturday, April 20th, and returning next Friday.Jerry K. ThorneEast Ridge, TN.

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Dave et al.,One other thing: if I'm drifting off course that much, I would think (and prolly have thought actually) all this time that the course drift was caused by a steady wind at altitude which the forecasters hadn't picked up on. Magnetic deviations would be about my last guess. Also, maybe it's an interesting question to ask Canadian high-time arctic fliers vs Santo Domingeu

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Roger on the inertial navigation, Jerry. I remembered that a couple of hours after I posted.>I am off to Portugal again on Saturday, April 20th, and >returning next Friday. >Hope you have better luck with the luggage/equipment this time.Dave H.Fayetteville, GA

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>One other thing: if I'm drifting off course that much, I >would think (and prolly have thought actually) all this time >that the course drift was caused by a steady wind at >altitude which the forecasters hadn't picked up on. >Magnetic deviations would be about my last guess.You are definitely correct about the winds - and I'll be the first one to concede that they'll play games with you straying off course more than the VOR "can-o-worms" I dug up.If the forecast winds vary from observed, just remember the forecast is usually for several hours, and therefore it's not so much that the different winds have been unforseen, but rather it is just to be expected that they're gonna vary. I subscribe to a WX site where you can get very current, "every 6 minutes" winds every 1000 ft MSL from any NEXRAD site (if the sky is really, really clear it can't figure them out, though). About an hour ago I was looking at our area at 3000 ft, and 1 hour prior to the latest data, for 3 6-min "snapshots" of the winds, they were 270/10. The next 5 6-min periods they were more like 240-250 / 15.Maybe you've seen a text forecast, but for those that haven't, here's a "short" list for a "NINE" hour period. Guess how much the winds'll see-saw in "that" time frame ?FDUE04 KWBC 200223DATA BASED ON 200000ZVALID 201200Z FOR USE 0900-1800Z. TEMPS NEG ABV 24000FT 3000 6000 9000 12000 18000 24000 30000 34000 39000EYW 0607 0520+12 0615+09 0517+05 0226-07 0139-19 014735 014945 025156JAX 2913 3012+13 3309+08 3411+03 3322-08 3338-19 344235 343946 355157MIA 1006 0612+13 0615+08 0518+03 0125-08 0140-19 014035 024445 035556BTW, www.weathertap.com is the site, $6/mo. Really current radar - comes in handy working SKYWARN. Really good flexible Java tools for the radar. It is not a site for official wx briefings, yet it does provide just about everything one needs: TAFS, Freezing LVL, SIGMETS, etc., etc. I use it before checking DUAT (which Weathertap even has a link to) because it's just so quick. For those who know about Trade-A-Plane (TAP), Weathertap is an offshoot of theirs.Dave H.Fayetteville, GA

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From AVweb, 22 Apr :"Alaskan pilots better brush up on their VOR work. From Tuesday through Friday, the Air Force will be trying to jam GPS signals in the area of the Big Delta vortac. In case they're successful, the tests could disrupt GPS signals in a 310-nm area. The Air Force hasn't officially notified Alaskan pilots but AOPA found out about it and has been spreading the word. Pilots who encounter GPS interruptions are encouraged to report them to ATC or flight service and monitor 121.5."Dave H.Fayetteville, GA

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