[Skot]

I have recently bought X-Plane to assist me with IFR ground school training. However, I’m finding flight planning for navigation along federal airways a bit difficult using the X-Planes maps.

As an example, the FAA Jacksonville Sectional/Enroute L-24 charts have V157 on the 350 radial from Lakeland VORTAC. However if I refer to X-Plane’s Local Region / Low Enroute map, position the aircraft over the V157 airway (on the map) and click on the Lakeland VORTAC, X-Plane reports that I am on the 354 radial. The red compass rose that appears when you click on the VORTAC or any airport, aircraft ...etc, also shows the V157 from Lakeland at approx. 354 degrees (hard to get an exact reading). Initially I thought that the compass rose may have been aligned with True North, however applying MC = TC +W Variation (Lakeland is 4.1°W), would only produce further discrepancy to the FAA charts VOR radials.

Back to the cockpit... rotate the VOR receiver OBS, the CDI needle aligns centres on 350, fly the needle and I get to Ocala (COP Ocala 171 radial FAA charts). Interestingly, with no wind configured in the sim, I still have to maintain a magnetic heading of 355 to stay on the 350 radial in the C172 – a 5 degree yaw! (FYI – the HI was aligned with the compass). Ignoring this for the moment, I would have expected that X-Plane would display a VORTAC compass rose and reported radials aligned against the actual Lakeland VORTAC’s current configuration – ie. magnetic north when the VORTAC was last aligned (I’ve read that the FAA only re-align VORs when they get more than 6° out from magnetic north). Compass roses when selecting airports, aircraft ..etc, I would expect to be magnetic north, which seems to be the case. Alternatively, it would be useful if the X-Plane Low Enroute map, showed more information – ie. the to/from airway radials, intersection radials

Is my understanding of X-Plane’s display of VOR radials correct? –ie. they don’t match the FAA published charts

Is my expectation that X-Plane displays a VOR compass rose aligned against the actual VORTAC current configurations (ie. magnetic north when the VORTAC was last aligned) reasonable?

Other than using my paper FAA charts or www.skyvector.com, are there any x-plane plugs-in or better X-plane Low Enroute charts that can be installed which will allow me to better plan/report position during my x-plane flights?

I’m interested in whether anyone else comes up with same findings as myself – there’s a challenge for this afternoon

Cheers
Scott

[Bamboo Cougar]

Hey Skot
I have been having some of the issues that you describe as I teach myself IFR from books, tutorials and practise. It has been my assumption, with one single exception to date, that the problems I'm having are my ineptitude and not X-Plane's, but now I'm not so sure.
So the bottom line is... I can't help you with your questions so much but am keeping my eyes (computers and bberry) glued on this thread in case I too receive enlightenment .
Oh yeah... the one exception. It seems that torque and associated aero forces play a large part in drift in the simulator. I use 9.22 and its not so bad, but I hear things got real wild after 9.31... to the point where you could affect orbital trajectory of Earth if you left your Cessna tied down during a runup
Anyhow, wishing you luck and sharing. I am going to study this deeper now myself.
bc

[schufly50]

How close to the VOR are you when you get these bad readings? If your too far away from the VOR you will get bad readings just as if in real life. Thus having to switch over to the next VOR enroute for a more accurate reading. No way can x-plane be that far off. Your saying something like 6 degrees or something like that. Remember plus or minus 4 degrees VOR bearing error is legal for the FAA.

This post has been edited by schufly50: 27 February 2010 - 11:36 AM

[AndyGoldstein]

Scott - welcome to the zoo!

Actually, X-Plane is handling this situation exactly right. The issue is indeed magnetic variation, but it's going the other way. Here's the Lakeland VOR as it appears on the Tampa TAC at SkyVector:  LAL.jpg (205.82K)
Number of downloads: 30
I've extended the VOR's 360 radial to make it easier to measure. Put a plotter on it and you'll see that the VOR is set up with a 1 degree east magvar. Likewise, put a plotter on V157 and you get a true heading of 351. So that adds up. X-Plane has the correct 1 degree east magvar for the VOR in the nav database.

However... The actual magvar at this location is about 4.7 degrees west. X-Plane shows it as 4.1 west, because X-Plane's magvar table probably hasn't been updated in some years. Not too far off, though. So indeed, when you're flying the LAL 350 radial, your true heading is 351, and your magnetic heading is 355 or 356 (for X-Plane or real life, respectively). The discrepancy precisely matches the discrepancy between the VOR calibration and the actual magvar.

One final piece to the puzzle: The red compass rose that shows up when you click the VOR on the sectional chart is aligned to the local magvar. The little blue circle that is always displayed around the VOR is aligned to the VOR's magvar setting. Unfortunately it's a bit hard to read.

- Andy

[Skot]

Guys, thanks for your replies which have improved my understanding!

Summary:

Location reporting when you click on the VOR – The radial reported is based on local magvar from the compass rose, and not the VOR radial

Heading of 355 deg to stay on the Lakeland 350 radial - I’ve now found out that the Lakeland VOR was configured in 1965 when the local variation was 01E, and given the actual magvar at Lakeland is 4.1/4.7W, the magnetic course to maintain the 350 radial is 355/356 deg (Andy, as you said)

My Lessons Learnt:

Don’t assume that the radial is the magnetic course to fly, they only provide an indication of the course. There are several other factors to consider – VOR configured magvar, actual location magvar, and the FAA legal plus or minus 4 degrees VOR bearing error. Be ready to accept that the next VOR enroute radial may not be aligned with the previous for the above reasons. Use your plotter or flight planning software, and basically fly a heading appropriate to keep the needle centred.

Recommendations:

The following are my personal opinions, and if there’s mutual support I will forward to the development team -

When you click on a VOR in the Local Regional map, that X-Plane displays a VOR compass rose (blue instead of red to distinguish from local magvar) aligned against the actual VORTAC current configuration as defined in the nav database, instead of local magvar, and that the aircraft position is reported based on the VOR radials (maybe show both – ‘VOR radial’ and ‘Mag radial’, so you can determine both the mag course and OBS setting). Click any other object – airport, plane and display the current red rose showing magnetic course.

Make the existing blue VOR compass roses a bit clearer to read; alternatively the show to/from radials on the Low Enroute charts

What do you think? ... may be I should just use a flight planner

Cheers
Scott

[Guy]

I think you should use real IFR charts and forget about the X-Plane moving map.

[inktomi]

I agree that real charts are always better - but why not have the chart built into the system accurate as well?

Who wants to always be buying sectionals to fly in a simulator? I'll buy them for real world flights - and then use them in the sim - but even then, I'd want the built in charts to match..