VOR magnetic headings don't match up

[Finalfantasy]

Hi folks,
a quick question about VOR magnetic headings that can be found on VFR charts, e.g. along Victor airways. I'm looking at V611 out of SAF VOR going towards NELGE intersection. The chart says 232 degrees magnetic. If I measure this with a protractor I get a different number, more like 237 degrees.
In fact, if I look at the compass rose on various VORs in the Albuquerque sectional, they all seem to display a 13 degrees difference from true north, rather than the expected 9 degree magnetic variation that is also on the chart.
Anyone know why? The only thing I can think of is that the VORs are not updated very often for changes in magnetic variation over the years, but I wanted to be sure of this since I have my checkride on Monday. My instructor doesn't know, so I thought I would ask here :)
FinalFantasy

[BEagle]

VOR transmissions are based on station declination promulgated at the time of commissioning, or as subsequently amended. They do not necessarily reflect actual magnetic variation at the transmitter site.

This: True course compared to VOR radials | Ask a Flight Instructor (http://www.askacfi.com/3857/true-course-compared-to-vor-radials.htm) might be of interest to you.

Good luck with your check ride!

[Gertrude the Wombat]

VOR transmissions are based on station declination promulgated at the time of commissioning, or as subsequently amended. They do not necessarily reflect actual magnetic variation at the transmitter site.

I once mentioned that the aircraft I'd just hired had a five degree difference between the indications of the two NAV receivers tuned to the same VOR.

They fell about laughing and said I'd obviously rented the plane on a good day.

[Above The Clouds]

The magnetic track between two VOR's is measured in the middle of the airway, so the outbound radial from one beacon will not be the same as the inbound track to the new beacon.

[foxmoth]

VOR magnetic headings
If you are doing a test you should make sure you get the terminology correct - Out of a VOR you have Radials - these are magnetic (sometimes true in high Northern latitudes) TRACKS away from the beacon - not headings, which are the tracks adjusted for wind!

[Cows getting bigger]

.... aaah, but the point is that the radials are not necessarily magnetic track from a beacon. They assume a constant declination which is ordinarily a mean of the variation at the facility over a period of 5 years. :eek:

If one were to peruse the ENR section of the AIP, you would notice that each VOR has a declination and variation as part of it's description. For example from the UK AIP:

JERSEY VOR/DME 1.3°W (2015) 2.14°W

In other words, the Variation in 2015 is averaged at 1.3°W but the VOR is set-up with a declination of 2.14°W; there is a 0.8° difference between VOR radial and the magnetic track required to maintain that radial. Fortunately in my part of the world that difference is ordinarily negligable. :)

[Finalfantasy]

Wow, thanks you all for your prompt replies. I learnt (and re-learnt) a lot: declination versus variation, track vs heading.

The latter mistake I am embarrassed about since I already have a JAR PPL... :rolleyes:

Anyway, on Monday I'll hopefully become the proud holder of an FAA PPL... all part of my cunning plan to then get my IR.

Thanks again,
FF

[Big Pistons Forever]

Anyway, on Monday I'll hopefully become the proud holder of an FAA PPL... all part of my cunning plan to then get my IR.


If it is a USA IR than you can forget all this nonsense and enjoy direct GPS routing to pretty much everywhere.

:)

[ChickenHouse]

We are discussing 5 degrees for VOR bearings ? If two indicators in the same cockpit agree by more then 10 degrees, I would be happy. Mine are different by about 10 to 15 degrees when tracking VORs and I don't see this as an issue. If I calibrate it lasts for about 3 month and they are off again anyways (and yes, I know KI214 don't earn best reputation).

[olasek]

>> If two indicators in the same cockpit agree by more then 10 degrees, I would be happy

I hope you meant to say by less than 10 degrees.
In the club aircraft I fly they all agree by 4 degrees or less (requirement for IFR flight) and I don't see this as a big deal in a reasonably well maintained airplane. If they agreed by more than 10 degrees .. no, I wouldn't be very happy. And by the way digital VORs are super accurate. Bu perhaps in Nairobi you may have a different expectations - even a turning propeller is a reason for joy.

[ChickenHouse]

I know the requirement for IFR, but we rarely meet ... We say, if you have a turning prop in front of you, you may have hit the flight schools cessna, 'cause I now fly small jet.

[A and C]

The reason that your VOR falls out of adjustment after about three months is due to the quality ( or lack of it ) of the adjustable resistors that are the standard King fit.

If you have a good radio shop they can fit high quality sealed adjustable resistors that will not wander off setting.

A year after having this work done the guy doing this years radio annual check remarked on how accurate both VOR units in my aircraft are.

[porterhouse]

... aaah, but the point is that the radials are not necessarily magnetic track from a beacon.
And this is the only correct answer here, VOR radials indeed don't necessarily match magnetic heading, in the western US the difference is already approaching 5 deg as it was observed above, in Florida for example it will be a smaller number.