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TChapman500

VOR Navigation Issues

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Here's the situation.

 

1) I create a flight plan to go from the Dallas-Ft Worth airport to the Denver International Airport for FL350 with IFR.

2) I use the VORs that are used in FS98 instead of having them auto-assigned by FSX.

3) I use the headings listed in the flight plan and tune the radios to the correct VOR frequencies, navigating by what the results are.

4) The headings listed in the flight plans take me almost 10 degrees off course (according to the GPS) to the left or right seemingly in random order..

5) ATC does not like what I'm doing and they take me off of my intended course.

 

What happened?! How is it that I end up off course by 10 degrees when using the VORs to navigate when the flight plan tells me to fly those headings. EG: On one leg of the flight, the flight plan says to fly a heading of 317 towards the VOR. As it turns out, it's 309 that puts me on course. 309 is not a heading that is listed anywhere in the flight plan. There is a 310 on the final leg of the flight to get me lined up with the runway, but the headings listed are:

 

NUM - VOR ID - FREQ - HEADING IN/OUT

1) SPS - 112.7 - 305/317

2) LAA - 116.9 - 317/303

3) HGO - 112.1 - 303/310

4) FQF - 116.3 - 310/333

 

These headings do not give me the course that the GPS gives me. In fact, it seems that if I were to go strictly by these headings, I would have to make a large turn to one direction, then the other, just to center the HSI. Is there a better way to get the headings required so that the outbound portion of a leg from a VOR puts me directly in line with the inbound portion of the next VOR? What FSX gave me does not line up the VORs correctly.

 

According to the FS98 help for the flight, the headings are as followed:

 

Num - VOR ID - HDG IN/OUT

1) SPS - 320/313

2) LAA - 308/298

3) HGO - 298/300 (just before FQF)

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If you fly inbound to a VOR and this VOR is also a GPS waypoint you will be right on the spot.

 

But remember - the further away you are from the VOR the bigger the error (in miles) may be for 1 degree plus or minus. The flight plan only gives you the next whole number. Let's say the GPS path is actually at 278.3092 degrees and the plan says 278 degrees!

 

This could be approx. 11 miles at a 80 miles distance.

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Magnetic declination or variation, http://en.wikipedia.org/wiki/Magnetic_declination , and cross wind correction can both contribute to what you are seeing. I don't know which plane you are flying but, in most cases, you can press and momentarily hold the "d" key to adjust your HSI for magnetic variation. If you are flying a G1000 or some of the Garmin GPS's, you can see the cross wing indicator on the screen. ti's explanation and either or both of these can give you the kinds of errors you are seeing.

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Its a tricky subject, the VORs are aligned to magnetic north, are you using magnetic north? The HSI should be aligned to magnetic north though, It could just be that its all out of date and out of sync, i.e. the VORs are pointing to what was magnetic north 7 years ago but your using a flight planning software with todays variation. I have never noticed it as a problem in the sim with the VORs though.

 

There is often a difference between the runway headings and what modern plates will show.

 

What are you flying? a modern 737 actually automatically uses a combination of INS (and I think GPS) for positioning and only cross references with the VORs to chek for inertial drif, so use the FMC for navigation.

 

If you are flying a GA type such as a Baron then you probably would be daisy chaining VORs together into a route, then your a bit stuffed.

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Boeing 737-800. I compensated for wind direction. I'm talking about the course heading, not aircraft heading for the VORs.

 

Outbound on SPS, the HSI told me I was on course while the GPS told me I was 10nm to the right of my course.

Inbound on LAA, the HSI told me I was on course (once I had turned almost perpendicular to the course to intercept and back to the course heading) while the GPS told me I was 20nm to the left of my course..

For the rest of the flight, I was only slightly off course according to the GPS, while the HSI told me that I was on course.

 

In other words, even though the HSI told me I was on course, when I switched to the inbound VOR frequency, I had to turn almost perpendicular to the course to intercept it every time just so that the HSI told me that I was back on course. The GPS however, said that I was off course almost the entire flight.

 

Is there any way to save the course that the plane took so that I can show you what is going on?

 

[EDIT]

I'm using the headings that the default FSX flight planner has told me to use.

[/EDIT]

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Too late for that, However, to give you a picture of what happened, the map shows that I'm slowly drifting off course when I'm outbound, when I switch to the next inbound VOR, it shows me cutting across the course, then slowly drifting towards it. It appears to be about a 5-degree difference between the course of the map, and the course of the HSI. For the first leg of the trip, which was the longest, I drifted ~10nm to the right of the course, then shot across it to ~22nm to the left of the course, then drifted back onto the course, landing on course it right at the VOR. For the rest of the flight, the same thing happened, but the distances were much shorter and I didn't drift towards or away from the course as much.

 

I'll send you the flight plan I used. Navigating by VOR without ATC. ATC will go by the course on the map, not the VORs. You must use the VORs to get the full extent of my problem. The ILS I used at the destination airport is 110.15, HDG 350. Descend to 7,500 before reaching the FQF VOR. Start descent outbound on HGO VOR or just before (CAUTION: Requires 2,000 fpm+ descent rate). Make sure the flight plan is loaded so that you can see where the aircraft went relative to the course displayed on the map. Cruise altitude is 35,000 feet. Again, do not use ATC. Use only the VOR radios and HSI to the frequencies and headings listed below, and look at the results.

 

SPS - 112.70 - In 305 - Out 317

LAA - 116.90 - In 317 - Out 303

HGO - 112.10 - In 303 - Out 310

FQF - 116.30 - In 310 - Out (Tune ILS 110.15 - HDG 350)

 

KDFW_to_KDEN_FL350.zip

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I will try and take a look after work but I am going to be quite busy trying to modify my setup to try out DX10 mode again.

 

Hopefully someone else will pop by with the solution shortly!

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Guest

I'm using the headings that the default FSX flight planner has told me to use.

 

Maybe you shouldn't do that but simply tune into the VOR and fly directly to it...? So tune in, turn until the CDI is centered and TO is activated and then keep the CDI centered (which may require a slightly different heading if there is wind). Seems to me that would solve the problem (although I still am not entirely sure what's going wrong where :wink: )

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Like I said, I compensated for wind. The aircraft heading does deviate a couple of degrees from the course heading when there is a wind, but the course heading itself deviates by about 5 degrees to the right of the course that's on the map.

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2) I use the VORs that are used in FS98 instead of having them auto-assigned by FSX.

 

???

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Are you using the default FSX VORs and, if not, which VORs are you actually using?

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Again, don't use the flightplans headings but use the CDI to get to the VOR. Headings created by planners aren't the actual radials you need to fly to get to a VOR. Some time ago I tried to figure out radials that would lead my to an airport (using triangulation) using Plan-G but the headings the planner gave me never were the actual radials I had to fly. It just doesn't work like that, apparently. It all has to do with magnetic north and how the deviation changes when you move around.

 

When you navigate using VOR you have to actually USE them and not rely on headings calculated in a planner. Use the VOR the way it is intended and not only as some kind of landmark to fly towards using calculated heading without actually using the radials of the VOR! It doesn't send out signals for nothing! :wink: It's a waste if you don't use the information the VOR is presenting you!

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Thats a good answer, but I think the OP is having to navigate OUT on a specific radial for a certain distance (probably it defines the airway) to the half way point, and then navigating IN on the second VOR.

 

 

e.g. I would expect (in RL) that I could dial in (for example) the 330 radial which might define a particular airway. I would head NW along that radial and at the half way point tune in the VOR at the other end of the segment and come IN along the 150 radial. In RL for the VORs would be close enough (if they were defining a airway segment) such that the difference in magnetic variation between them was negligible.

 

Tried to download the .zip but it wouldnt

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as you move along any line between any two waypoints the compass direction to/from the waypoints changes with your movement

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Thats a good answer, but I think the OP is having to navigate OUT on a specific radial for a certain distance (probably it defines the airway) to the half way point, and then navigating IN on the second VOR.

 

e.g. I would expect (in RL) that I could dial in (for example) the 330 radial which might define a particular airway. I would head NW along that radial and at the half way point tune in the VOR at the other end of the segment and come IN along the 150 radial. In RL for the VORs would be close enough (if they were defining a airway segment) such that the difference in magnetic variation between them was negligible.

 

The problem is that the OP isn't using (specific) radials but headings that come from a planner. In your example, when flying towards a certain airway, you would use published numbers to get there: an airway is specified and known and documented. You never try to fly to an airway or an intersection using headings you figured out yourself as the OP is trying to do (afaik). That won't work.

Also, figuring out where a specific point is in 'space' will lead to different results depending on where you are when you calculate that point.

And finally, "the difference in magnetic variation between them was negligible" doesn't apply when flying towards specified intersections or known points of triangulation because the people who published those numbers took note of magnetic deviation, so if for instance an approach chart says an approach fix is at a certain point where two radials intersect, you can be sure they numbers are 100% correct. :wink:

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And finally, "the difference in magnetic variation between them was negligible" doesn't apply when flying towards specified intersections or known points of triangulation because the people who published those numbers took note of magnetic deviation, so if for instance an approach chart says an approach fix is at a certain point where two radials intersect, you can be sure they numbers are 100% correct. :wink:

 

Yeah thats what I meant, but not in so many words.

 

If the OP is using the headings he calculated then that would be the source of the problem, but I was giving him more credit than that. It sounds to me like he knows very well what radials are supposed to intersect to define his airway.

 

Maybe I have misunderstood.

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Yeah thats what I meant, but not in so many words.

 

If the OP is using the headings he calculated then that would be the source of the problem, but I was giving him more credit than that. It sounds to me like he knows very well what radials are supposed to intersect to define his airway.

 

Maybe I have misunderstood.

 

Or maybe I have misunderstood. :wink:

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Tried to download the .zip but it wouldnt

Fixed it.

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Again, don't use the flightplans headings but use the CDI to get to the VOR

What is CDI?

 

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When you navigate using VOR you have to actually USE them and not rely on headings calculated in a planner. Use the VOR the way it is intended and not only as some kind of landmark to fly towards using calculated heading without actually using the radials of the VOR!

Huh? You're not making any sense! Do you even know what I mean by COURSE HEADING? It's the direction that the airplane flies to get to a specific point. NOT the direction that the nose is physically pointing towards! There are two heading selectors on the autopilot panel. One is the direction that the nose of the aircraft points to, and it's labeled "Heading." The other is the trajectory that the airplane flies, and it's labeled "Course." I put the headings listed into the flight planner into the selector labeled "Course." The HSI tells me that I'm on course, while the map shows that I'm on a ~5 degree trajectory to the right.

 

For the entire flight, outbound I'm drifting away from the course, inbound, I have to make a 90-degree turn to the left, then to the right, and now I'm drifting towards the course. The entire time, the HSI tells me that I'm on course.

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I reckon you should bin that flight plan. Dont try and emulate something from FS98 or whatever, life is complicated enough. Just get a new flight plan, a real one, use the VORs in FSX, and / or use the FMC. There are websites where you can download a real flight plan for the trip from Denver to Dallas or whatever your trying to do.

 

Real 737 pilot does not have a list of headings, at least not that he is actuallly following. He simply has a clearance; join airway ABC123 at intersection XYZ and leave at XZY. He is not flying around fiddling with the CDI. He is flying magenta line on his PFD. In fact the autpilot is doing it all in LNAV mode. So what your doing is not realistic for 737, after 200 series anyway.

 

I think you are being a bit rude to J van E, who is trying to help and has better things to do. He very well knows about courses and headings, he also knows what a CDI is.

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Huh? You're not making any sense! Do you even know what I mean by COURSE HEADING?

 

LOL It would be a bit said if I didn't know the difference after 4,557 posts on this forum. :wink: I am just trying to understand what's going wrong with your flight. If time permits I will see what happens on my PC when I try to fly towards a VOR using the heading that a flightplan is giving me instead of using the VOR itself to get there. For now I will repeat again that it's a bit odd to tune into a VOR but to NOT actually use it but to use headings from a flightplan instead...

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Do you even know what I mean by COURSE HEADING?

 

I don't. There is a course and there is a heading. There is such thing as a COURSE HEADING.

 

There aren't FS98 VORS in FSX either.

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Bold texts indicate quotes from portions of the post.

 

------------------------------------------------------------------------------------------

 

I reckon you should bin that flight plan. Dont try and emulate something from FS98 or whatever, life is complicated enough. Just get a new flight plan, a real one, use the VORs in FSX, and / or use the FMC. There are websites where you can download a real flight plan for the trip from Denver to Dallas or whatever your trying to do.

 

Real 737 pilot does not have a list of headings, at least not that he is actuallly following. He simply has a clearance; join airway ABC123 at intersection XYZ and leave at XZY. He is not flying around fiddling with the CDI. He is flying magenta line on his PFD. In fact the autpilot is doing it all in LNAV mode. So what your doing is not realistic for 737, after 200 series anyway.

 

I think you are being a bit rude to J van E, who is trying to help and has better things to do. He very well knows about courses and headings, he also knows what a CDI is.

 

"I reckon you should bin that flight plan."

What do you mean?

 

"Dont try and emulate something from FS98 or whatever, life is complicated enough."

That was my favorite flight in FS98.

 

"Just get a new flight plan, a real one, use the VORs in FSX, and / or use the FMC."

By use the VORs in FSX, do you mean the VORs that the FSX flight planner wants to assign me? What exactly do you mean by FMC? FSX just has a black screen-like object with a few dozen buttons below it for the flight management system.

 

"There are websites where you can download a real flight plan for the trip from Denver to Dallas or whatever your trying to do."

FSX compatible?

 

"Real 737 pilot does not have a list of headings, at least not that he is actuallly following. He simply has a clearance; join airway ABC123 at intersection XYZ and leave at XZY. He is not flying around fiddling with the CDI."

First, what is CDI? Second, what's the advantage for using these airways over the VORs with the in/outbound headings being put into the Course selector?

 

"He is flying magenta line on his PFD. In fact the autpilot is doing it all in LNAV mode."

There are some things about the autopilot that I do not trust. Non-VOR navigation is one of them.

 

"So what your doing is not realistic for 737, after 200 series anyway."

What I'm doing is exactly what I would do in FS98. The co-pilot would tune the NAV radios to the VORs, and input something into the course selector, and I'd follow the course indicated by the HSI. There were almost no course corrections after switching from the outbound frequency to the next inbound frequency.

 

"I think you are being a bit rude to J van E, who is trying to help and has better things to do. He very well knows about courses and headings, he also knows what a CDI is."

I'm trying to clear out what appeared to be contradictory instructions. And I was actually asking him what a CDI is.

 

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LOL It would be a bit said if I didn't know the difference after 4,557 posts on this forum. :wink: I am just trying to understand what's going wrong with your flight. If time permits I will see what happens on my PC when I try to fly towards a VOR using the heading that a flightplan is giving me instead of using the VOR itself to get there. For now I will repeat again that it's a bit odd to tune into a VOR but to NOT actually use it but to use headings from a flightplan instead...

 

 

"LOL It would be a bit sad if I didn't know the difference after 4,557 posts on this forum."

Sorry.

 

"I am just trying to understand what's going wrong with your flight."

When I put the headings into the course selector, I end up on a trajectory that is ~5 degrees off from where the map says I should be. And I'm trying to find a way to get the headings needed for the course selector right without having to repeat the flight several times and note down the new headings for the course selector.

 

"If time permits I will see what happens on my PC when I try to fly towards a VOR using the heading that a flightplan is giving me instead of using the VOR itself to get there."

Huh? I was using the VORs to get me there. The headings that I got from the planner are the headings I put into the course selector. I just left the heading selector to the default selection.

 

"For now I will repeat again that it's a bit odd to tune into a VOR but to NOT actually use it but to use headings from a flightplan instead."

What do you mean? I put all of the headings into the course selector. I was using the VORs exactly the way I'm used to using them.

 

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I don't. There is a course and there is a heading. There is such thing as a COURSE HEADING.

Thanks for clearing that up for me.

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