A bad night

[flyingdrill]

Flying a simple TEC route from Burbank to Bracket. Using Carenado's Stationair in X-Plane 10.36, with current Navigraph data. Initially, I flew this on the correct VOR radial from VNY. This is shown as 095 radial on the DP chart, but V186 is shown as being on the 097 on the L4 chart. My eventual track turned out to be parallel but just to the S of the airway's magenta line on the Garmin 530. It's not a huge deal, but one is supposed to be on the centre of the airway, so whether the VOR readout (double checked on NAV 2) or the magenta line was correct, I have no idea. Never mind. I decided to go with the Garmin, and that was fine.
I was given vectors to the field, and was to report in sight, when I was cleared for the visual on 26R.

Then X-Plane went into one of its long freezes, which it always seems to do for me a few miles West of Ontario. That disconnected me from my iPad, which I use FlyQ EFB on. I was discussing the visual approach with the controller, when he informed me that I was heading for the wrong field. What a mess. After I was in violation of my clearance, I confirmed I was in VFR, and eventually spotted KPOC, with some assistance from the controller. It can be a little difficult, sometimes, to spot a field when one is low in X-Plane.

Oh boy! Well, it gave some entertainment to the others who were on frequency, and I can now hang my head in shame...... It goes to show how a distraction can throw you, when you've had a tiring day, and one is then flying at midnight.

I had also been listening to some others who were messing things up, and it was only right that I joined their club

[Nelson L.]

so whether the VOR readout (double checked on NAV 2) or the magenta line was correct, I have no idea.

I'll quote Peter:
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Welcome to the world of "declination", which is sort of like "variation" and "deviation" that most pilots are familiar with.

As you most likely know true north and magnetic north aren't in the same place, for various technical reasons aviation uses magnetic north for most navigation purposes.

What you may or may not know is that the magnetic north pole moves at a slow rate, this means that over time the course between 2 points will change as the magnetic north pole changes.

The government remaps the lines of variation every 5 years or so and updates IFR/VFR charts. However, they do NOT reprogram the magnetic north of VORs (way too much time and money to do so). Additionally, your GPS uses current (in some cases more current then the government data) magnetic variation data to determine courses between points.

So this means the VOR and your GPS are using different "magnetic north pole" points, which causes these small course errors. The "assumed variation" of a VOR is called "declination".

Using your specific example:

The true course from OCN to KELPS (first point on V23) is 316. The declination of the OCN VOR is 15E (determined in 1965...), making for a mag course of 301, hence the use of the 301 radial from V23.

Now let's look at the modern day GPS. The actual current variation near the OCN VOR is 12E (determined from the section chart which uses 2010 data). If we take our true course of 316 (which doesn't change) and take out 12, we get 304, or what your GPS is using.

So that's what's going on.

A couple of questions people have on flying this.

Using a VOR what course do I dial in? 301 (the VOR Radial)
Using a GPS what course do I dial in? 304 (what the GPS says)
What heading do I fly (assuming no wind, or to base wind correction angles off of)? 304
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Hopefully I understood you right and didn't quote something randomly that has no relation to the question Regardless, I understood everything above until we started talking about assumed variation. I've given up at this point and just go with it...

[Peter Grey]

Hopefully I understood you right and didn't quote something randomly that has no relation to the question Regardless, I understood everything above until we started talking about assumed variation. I've given up at this point and just go with it...

That's the post I would have quoted if I saw the question before you did.

[Edit: Ignore this post, I misread the original post, see below]

[RyanK]

V186 is the 095 radial from VNY, not 097. That error would put you south of the airway like your GPS showed. I'm guessing you read the 097 from the FIM-VNY segment. It happens to be the case that there's about a 2 degree difference between the declination of VNY and the local magnetic variation on the sectional, but I don't think that was the issue here.

[Peter Grey]

Actually Ryan is right here. I misread the original post, this isn't a GPS vs VOR issue, but a chart misread.

V186 is the 095 radial from VNY. It's the 097 radial from FIM to VNY.

[Nelson L.]

Don't be lazy and reply to a thread before first looking at the chart in question kids

(not skimming helps too...)

[flyingdrill]

Firstly, thank you all for not telling me what an idiot I was with the last bit of the flight. I am one of only 11 people on PE to have completed the Alphabet Challenge, after all
The controller took me off the TEC route to give me an early direct to the field, gave me a heading and told me where to expect to see the field. I saw it (or was it?), and positioned myself on the downwind, corrected a heading and then sailed past to find myself flying into Cable (I think it was). Just not paying attention. I was not paying attention to the 530 either, the large 2D window of which I had dismissed, as I thought I no longer needed it. The tiny lettering on the 3D panel screen was not what I was looking at, and my wonderful backup IEFB on the iPad was gone, because X-Plane had disconnected when it froze on me. See, fatigue, late at night, a couple of glasses of wine over dinner, and there you go. It was only when I looked a bit more carefully at the runway as the controller asked me what I was doing, that I realised I was not at KPOC, which is what he told me! Only retrieved by a beautiful approach and landing at KPOC but, by then, I was covered in embarrassment

Actually, Nelson, it was not the declination thing with me in this case - I know about that. Although it is declination at FIM and VNY that accounts for the 2 degree difference along V186, which is completely straight on the chart.

Ryan and Peter got it! I just read the chart in a hurry last night (around midnight UK), and read the 097 off the beginning of V186 at FIM, rather than the 095 which it clearly says off VNY - matching the DP chart. Simple. I then set my OBS as 097 instead of 095. My fault for not reading the L4 properly.

[Flying Penguin]

Whilst I can't offer any sage advice, I'm glad you managed to round it off in a beautiful landing

I have to admit, the running commentary you were giving made my night

Cheers

Jamie (the idiot heckling from 8DB )

[flyingdrill]

Jamie,

I just flew it again, perfectly in PE. Much better at a sensible hour.

KPOC and Cable are pretty close to each other, as are many other fields in S. Cal., as you know. That particular area of my X-Plane scenery is just a flat brown area, almost like a huge ploughed field, with very few distinguishing marks.

Very glad I gave you (and probably a few others) some entertainment

[Nelson L.]

fatigue, late at night, a couple of glasses of wine over dinner, and there you go.

Am I the only one who thought of Ty?