This was originally a problem I noticed with the 727, but I realized that it is not the aircraft, but a simulator issue. No matter what VOR I'm flying, the course given to me by my VOR indicator is slightly off from the actual course on the GPS (correct heading, but wrong positioning). This occurred on my old system and has not stopped on my new one. Is VOR navigation supposed to be a bit off? Does anybody else have this problem?

Thanks,
boeing247

boeing247,

Here is a screen capture of the CS 707 on airways to the EMI VOR.
All looks normal on the VOR display and the GPS.

http://img109.imageshack.us/img109/3558/707vorgps.jpg

Lou

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So you've never had any problem like this?

No, not as you are describing. But in the older planes such as the 727 & 707 I do not use a GPS, only VOR's. Yet, as you can see the VOR and the GPS are lined up. Maybe Mark can shed some light since I think he uses GPS in the old birds.

Lou

I don't use the GPS in old planes, but I was vectored back on course by ATC, so I checked the GPS and I was one or two (sometimes more, depending on the VOR) off course event when the HSI said I was perfectly fine. Also, this is occurring on modern prop planes, too.

LOU wrote on Jul 22^nd, 2011 at 6:36pm:

No, not as you are describing. But in the older planes such as the 727 & 707 I do not use a GPS, only VOR's. Yet, as you can see the VOR and the GPS are lined up. Maybe Mark can shed some light since I think he uses GPS in the old birds. Lou

That's nice to know Lou. When boeing247 first brought the subject up a while ago, I had the exact same problem as he did. I was offtrack by up to 2 miles and increasing. The VOR showed that it was following the track, but even when I tried it with no winds (Clear skies), you could see it wasn't going to go over the VOR. It was definitely going to miss. By more that two miles!

Mark

Try something for me...

Find a VOR that you can see or find from the air.
On VFRMAP.com plot a radial to another VOR that is not too far away, lets say 40 to 60 miles.
Fly the radial from one VOR to the other using the plotted radial and see if it takes you right over the second VOR.

I did just that, and here is what I found.

http://img94.imageshack.us/img94/2396/ottvor.jpg

I plotted a course from the OTT VOR to the SBY VOR.
The radial from OTT is 120 degrees.
When the needle indicated station passage I froze the sim and took these captures.

http://img39.imageshack.us/img39/3166/ottvorinside.jpg

http://img708.imageshack.us/img708/7537/ottvoroutside.jpg

http://img192.imageshack.us/img192/1153/ottvorgps.jpg


The GPS is dead on as is the VOR.
The depiction of the plane in the GPS is facing the wrong way because
I hit the "Y" key to bring the plane down in altitude.
The distance from OTT to SBY is about 50 miles.
At 60 miles, one degree is one mile wide.

I have not seen a problem with the VOR vs GPS.
Lets see what you all find.

Lou


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Lou is that just a black 727?

That is my super stealthy 727-100 !  :o

No Peter, it is indeed black.
That happens sometimes when
I pop in and out of FSX and
use several other programs
at the same time.

Lou

I've found something interesting: while flying, I was looking at the HSI, which was directing me off-course. I hadn't looked at the VOR indicator, which was giving me the correct course.

Here's the screenshot, it's actually from a Cessna C340, not the 727. (Does the 727 have a VOR indicator like this, or is it just the HSI?)

---

boeing247, are these displays from two different VOR's?

http://img819.imageshack.us/img819/1879/vor2x.jpg

If so, could be one of your VOR's needs to be calibrated.  :D

Just asking???

Lou

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No, they're the same. I have both VHF radios tuned to the same frequency.

You miss the point, you have two radios and two displays......
which one is feeding which instrument.

That is why I used two different colors.
Usually, one radio feeds the HSI and
the other feeds the second VOR dial.

Lou

No, I see what you're saying, I think I just phrased my response incorrectly.  ;) Yes, the top one controls the HSI and the bottom one controls the VOR indicator. However, they are bothed tuned to the same VOR station.

LOU wrote on Jul 23^rd, 2011 at 2:58pm:

Try something for me... Find a VOR that you can see or find from the air. On VFRMAP.com plot a radial to another VOR that is not too far away, lets say 40 to 60 miles. Fly the radial from one VOR to the other using the plotted radial and see if it takes you right over the second VOR.

Hi Lou.

I did a similar flight with the 727 yesterday. It worked perfectly.

http://i669.photobucket.com/albums/vv58/Markoz958/CS721_VOR_Tracking.jpg

Mark

Now I know why one was working and was wasn't--the working one was tuned to the wrong heading by one degree. So neither work.  :-/

Wow. Never heard of your problem. Does the Aircraft turn Earlier/Later and put you off course than the GPS?

What do you mean? (Sorry) The VOR is simply about 2 miles off of the GPS.  :-/

boeing247 wrote on Jul 26^th, 2011 at 7:52pm:

Now I know why one was working and was wasn't--the working one was tuned to the wrong heading by one degree. So neither work.  :-/

I do not think that that was the problem. The reason I say this is because when I changed my HSI to track the VOR along the correct heading, it was taking me away from the VOR and the course heading. In the end, I believe I would have missed the VOR by more than 2 miles. I was already 2 miles, and growing, off course. It was only getting worse.

I'm going to go and have another look at that Topic. I want to see if it still happens since I reinstalled FSX.

Mark

Folks, the problem is you're mixing apples and oranges.

http://img838.imageshack.us/img838/4615/vor1.jpg

The VOR is different than the GPS, in that the VOR is more accurate the closer you get to the station. At sixty miles from the VOR the width of one degree is one mile wide. If you make just a small error in placing the course in the OBS that will give you an error as well. GPS and inertial navigation do not have this problem.  Each VOR in the RW needs to be calibrated every so often. The VOT at certain airports will give you a check on the status of the VOR receiver and the display.

If you're flying a VOR radial on a high altitude VOR using Jet airways, you could have legs that are pretty far apart and thus have slight errors in tracking the airway. You cannot compare the VOR and GPS when you are a long distance from the VOR.

Lou

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Oh, okay. Then how do you stop ATC from correcting your path?

If you fly the VOR's properly - correct radial, and change at the change over point - you should be close enough to the center line of the airway to be OK.

Lou.

I believe that the one in another Topic is an FSX error (and again just now). I flew it again last night. Flying this VOR to VOR route:
KMSP MSP DWN ABR DPR GCC DNW IDA HLE BOI KBOI
The problem is between DWN and ABR. Look at the 3 images to see what is going on.

http://i669.photobucket.com/albums/vv58/Markoz958/DWN-ABR_1.jpg
The first one, I am heading for DWN using HDG mode. I am 5 miles away and the VOR track from DWN to ABR is supposed to be 276^o.
My VOR is set to ABR and the course is 276. Notice that according to the PFD shows the track over to my left?

http://i669.photobucket.com/albums/vv58/Markoz958/DWN-ABR_2.jpg
In this one, I'm in NAV mode (not GPS mode). My aircraft is heading on a course of 244 to intercept the track. I am 6.31 nm from the GPS track between the two VOR, and I have not intercepted the VOR track yet.

http://i669.photobucket.com/albums/vv58/Markoz958/DWN-ABR_3.jpg
In this third one, I am 13.6 nm from the GPS track, and my aircraft is trying to track the VOR, but it can never quite reach it.

The question is this. IF the tracjk between DWN and ABR is 276^o, why can I not intercept the track until I am 13.6 nm to the left of where it should be?

Everything you tell us is true and correct, but in this instance, the VOR track in FSX must be wrong and following you guide;lines will not fix this.

Boein247 pointed this out in this Topic (same link as berfore). Can you try it to see if we are wrong? I also had problems in the following aircraft 727-100 (Captain Sim), C-130 (Captain Sim), Baron B58 (Carenado), C340 II (Carenado), Lear45 (MS) and the F-14 Tomcat (Iris). I do not beleive it is Captain Sim or other developers fault. It must be FSX at fault.

Mark

Mark,

Sorry To take so long to get back. The BB messed up my account so I am operating on a "new" account. CS-2 is attempting to correct the problem.

I do not know anything about this Nav Log. I would have to get a real chart and see if the routing is the same on paper as it is in this Log.

If the routing is the same, then there is a bug in FSX (big surprise).  :o

When I fly from place to place, I use either a VFR map or an IFR chart and make up my own routing. Since I don't use VATSIM or FSX ATC, I never seem to have a problem navigating, I still fly the center line of the airway and cross check with objects on the map or the GPS. If the data in FSX is correct, the VOR and GPS should be the same - within a small margin of error (slightly off on the OBS, etc.)

Try http://vfrmap.com/ and use either a VFR map or use a IFR low or high chart and fly the routing using one of these charts. Check it with the GPS. If you find you are not on the proper course I guess it is then something in FSX.

Lou