VFR Plogs and 'Magnetic Track'

[Superpilot]

I've just come across a VFR plog with a column for 'Magnetic Track', never seen this before!

True Track is what you deduce via chart plotting.
Add Winds to that and you get True Hdg
Compensate for Magnetic Variation gives you Magnetic Heading - which is what you fly

I may be overlooking something here (if so drop it to me gently!). My question, on a standard VFR plog, why would you need the Magnetic Track, what purpose does it serve?

[IO540]

Mag track is what a GPS displays.

It is also what you are tracking if tracking a VOR, or tracking an ADF.

[EGBKFLYER]

Remember "Cadbury's Dairy Milk - Very Tasty" or "True Virgins Make Dull Companions"?

Convert True to Magnetic by allowing for magnetic Variation (found on your chart).

A track is what you trace over the ground - can be true (related to true North) or magnetic (related to magnetic North)

As IO says, mag track might be useful to note if you're flying using VORs or GPS (though you can configure GPS to display True tracks btw). Personally, I only note magnetic tracks on my own plog, since they aren't much different from true tracks in the UK and it saves having lots of track figures on the plog.

Hope that helps

[bookworm]

I'm not sure that anything with a true north reference has much place on a plog. Better to use a single reference and make everything magnetic. Calculating e.g. approximate drifts is rather more complicated if you're comparing a true track with a magnetic heading.

In the UK in particular, the variation is small and the forecast wind direction is only given to the nearest multiple of 10 degrees, so it's not going to change anything to use magnetic. To the precision to which it is appropriate to make the initial plan, you can forget the difference between true and magnetic in the wind. That leaves only the measuring off a chart, which is easy to correct for variation to a degree.

IFR navigation (everything to do with VORs, airways, instrument approaches) is done using magnetic tracks. Why do it differently for VFR?

[BEagle]

My preference would be:

1. On the ground pre-flight - measure tracks in true, use true W/V, add variation, obtain planned mag hdg.

2. In flight use mag hdg and mag trk for the reasons stated above. (Unless using true on oceanic flights!).

3. If you need to measure a track on a chart in flight use the nearest convenient VOR rose and the edge of the checklist as a 'parallel rule'. Actually easier than it sounds!

[IO540]

I haven't done anything with true north for as long as I can remember. It's only in the exams one needs to do it.

There are places in the world there the mag variation is so huge they have to use different procedures, but this doesn't apply anywhere in Europe.

[Superpilot]

A question that's plaguing me then...
My Plog contains (best viewed in full screen):

From¦To¦MSA¦Alt¦True Trk¦Winds¦True Hdg¦Mag Var¦Mag Hdg¦Distance¦TAS¦GS¦ETE/ATE¦ETA/ATA¦Fuel used/rem

EGTR¦LAM¦21¦2400¦092¦180/20¦102¦2.5W¦105¦18¦105¦103¦11 / ¦ / ¦ 4.1/124.9

Direct track from EGTR to LAM is 092. I wish to track 092 (true) inbound to LAM from the West but as you say VOR's use magnetic track. Therefore what do I select for the OBS? Is it 092 (True Track) + 2.5W Mag Var, and therefore 095? Because I have flown with many a pilot who simply set the OBS to the Magnetic Hdg for that leg!

In which case, on a VFR plog, when tracking to a VOR, is it more correct to create and use a 'Mag Track' column instead of the existing Mag Hdg column?

Thanks for clearing this up for me.:ok:

EDITED TO SAY: I've just re-read something above and all makes sense now. Thanks for all your input.

[EGBKFLYER]

095 is right - see my post above...

If you have a True track on your plog, correct for variation and you will have your mag track for that line you've drawn (095 in your example). This is the number for your OBS.

Standard VOR CDIs as found in small bug smashers are not sensitive to heading, so putting a mag heading on the OBS is nonsense. You may as well pick any random number between 0 and 359!

Remember that heading is where the nose points, track is what you do across the ground. Following a line to a VOR or other point is tracking across the ground so you need a track bearing. You need a heading in order to make sure that you fly down your track.

[tmmorris]

Out of interest, Superpilot, do you have a PPL or NPPL? Am I right in thinking that in the NPPL people never learn to use a VOR?

Tim

[Whopity]

My question, on a standard VFR plog, why would you need the Magnetic Track, what purpose does it serve? Ever noticed the compass is Magnetic? Mag Hdg plus Drift =Mag Track! Why would you want to use TRUE? You can't steer it, VORs are Mag the RMI if you have one is Mag, the ADF is relative to Mag Hdg. Airways are Mag Tracks!

We used to operate C130s on Mag all the time.

[Fournicator]

Personally I have no time for the whole PLOG thing - just write tracks and timings on the map, and correct to give "winded" headings when airborne with MDR.

Saves having too many bits of paper floating around the cockpit - why have a map and a PLOG when you can put everything you need in one place?

And as for True tracks - how many GA aircraft have anything that needs True information? Surely better to keep it simple and all Magnetic?

[High Wing Drifter]

Ever noticed the compass is Magnetic? Mag Hdg plus Drift =Mag Track! Why would you want to use TRUE?
Because everything the Met says is TRUE and, with a VFR chart, one tends to align one's protractor to the lat/long lines so the two crucial bits of information you have are in TRUE until converted. Why convert two things for every leg, when simply creating a TRUE heading means you only have to do one? As mentioned, 3 degrees variation in the UK isn't exactly going to put you overhead LHR unless you got it all very wrong in the first place.

Granted, once you are comfortable with diversion planning, then it is much easier just to write everything you need on the chart directly and adjust in the air as necessary. But I doubt most will be comfortable with that until they have a few hours solo doing it the rigourous 'proper' way.

[Superpilot]

No, I have a full blown PPL, done in 2000 though. Had a break of 2 years, so forgot most things. Since then I have been maintaining it at a steady 1 hour a month (it costs a fortune around here). But thats way too little to retain knowledge! (And, that is my problem right now! :ugh: ). Hour building now for my commercial so really trying to get myself in gear, want to make sure I don't drift :p into any bad habits.

[IO540]

Standard VOR CDIs as found in small bug smashers are not sensitive to heading, so putting a mag heading on the OBS is nonsense. You may as well pick any random number between 0 and 359!

Stuff like above is going to confuse the hell out of somebody. It's also correct only if tracking a localiser!

On a standard VOR receiver instrument, called a CDI (course deviation indicator), when you are tracking a VOR conventionally (en route), you rotate the external circular bearing card so that your desired mag track as at the top.

In all normal operations the above track will be equal to your heading, plus or minus a wind correction, but normally the two will be similar.

Then, the CDI becomes a "command instrument" and the vertical bar tells you which way you should turn in order to become established on the selected track.

As you fly across the VOR (so now it is behind you) all that happens is that the TO flag changes to a FROM flag. Nothing else changes, you just fly along on the previous heading, and the bar still indicates which way to turn to stay on the track.

Because everything the Met says is TRUE and, with a VFR chart, one tends to align one's protractor to the lat/long lines

This is an irrelevant point (in Europe) but when you are passed a wind when landing, say "240/09" that is magnetic, not true.

It' s true that the lat/long lines on a map are on true N but a good way to plan (even if VFR) is with a VOR-VOR-VOR route, and the compass roses printed around each VOR are aligned on mag N. This is dead handy because you don't need a protractor; you just read the mag track straight off the printed rose.

I haven't used a protractor in years. But I must admit I use Navbox for generating plogs.

[Keygrip]

....and the semi circular/quadrantal altitude rules are based on Mag Track.

[Fournicator]

In my experience, very little of what the met man tells me is true, certainly not to the extent that I'd believe their winds so much as to worry about whether they were given as true or magnetic, at least not in blighty.

Don't get why you would have to convert two numbers to magnetic - surely true track to mag track then to mag heading = only one conversion?

And as regards writing on the map - I'd argue it's an easier technique to learn, gets people into good habits of actually looking out (a dirty concept for many PPLs I realise....), rather than faffing around with multiple scraps of paper in the cockpit. My technique is not lacking anything in "properness" or "rigourousness", it is after all taught by the oldest and most respected flying school in the world!

[High Wing Drifter]

IO540,
This is an irrelevant point (in Europe) but when you are passed a wind when landing, say "240/09" that is magnetic, not true.
Terminal wind is magnetic, because it relates to the runway (i.e. VOLMET, TAFs and METARs). Wind from met sources for flight planning is degrees true (i.e. forms 214, 414).
and the compass roses printed around each VOR are aligned on mag N. This is dead handy because you don't need a protractor; you just read the mag track straight off the printed rose.
Yup, this is part of the diversion planning technique I'm referring to. There is nowhere a pencil, a chart, 10nm thumb and a steady hand can't go :ok:

Fornicator,
Don't get why you would have to convert two numbers to magnetic - surely true track to mag track then to mag heading = only one conversion
True wind to mag wind too! You'll need that for a mag heading.
My technique is not lacking anything in "properness" or "rigourousness", it is after all taught by the oldest and most respected flying school in the world!
I agree! I thought I suggested as much. However, it is less rigourous in the sense that you don't scribe it all out in neat columns and show your workings out from begining to result. As you say, for all practical purposes it is not more/less accurate, hence the 'proper' in single quotes.

[Fournicator]

Thought I'd just made the point that, as the met man tells big pork pies anyway, i don't see much point in converting true wind to magnetic!

And as regards "showing your workings", the last time I did that was at University, it has no place in puddlejumper navigation. A quick clock rule / max drift MDR of the drift is well within the mental abilities of anyone who deserves to hold a pilot's license of any description.

[nzmarty]

Thought I'd just made the point that, as the met man tells big pork pies anyway, i don't see much point in converting true wind to magnetic!

which is fine if you're only dealing with 3 deg W, but when it's between 19 and 23 E, and 5000' winds are often 30kts, some calculation is needed, or you'll find yourself over a lot of trees, with nowhere to park

[Fournicator]

True, but let's face it, this forum is fairly well dominated with UK puddlejumper ops.

[High Wing Drifter]

It's always healthy to think generically though. However, the wind forecast is usually accurate enough that even I can arrive roughly where I should be even in a 74kts cruise puddlejumper. I don't think the issue is mental capability anyway, I think it is more to do familiarity. I can only speak for myself, but once I proved conclusively to myself that DR works very very well, well only then was I happy with trimming the process and working directly off the chart, etc.

[RatherBeFlying]

Draw line on map (airport to airport or via VORs).
Write takeoff time by departure a/p
Get on line and work heading to take out drift
Write time on map at significant points
Work out ETA to ensure sufficient fuel -- don't forget mixture. Your average digital watch has a countdown timer in hours and minutes. Set to fuel duration at planned power setting and you have an idea how long you have before you will be flying a low performance glider:p

[Fournicator]

HWD:

I take your point about thinking generically, but as long as you're aware of the assumption you're making (re: minimal change to wind vector from magnetic variation), I for one am quite happy to routinely make it.

I also agree about forecast winds, I'm just saying that I don't believe they're forecast to the accuracy where variation would make a significant difference to the accuarcy of the forecast. In addition, I definately couldn't fly a heading to an accuracy of the tiny percentage of a degree that four degrees or so would make to the calculated drift.

I still think there's a lot to be said for teaching people to mark mag tracks, timing marks, etc directly on the map, then use MDR to get a heading when airborne? If the technique works OK, and it does, why not teach the technique from the outset of navigation training?

[IO540]

What is MDR?

The winds aloft forecast is so far off, in both heading and velocity, it makes no diff whether you use true or mag bearings.

All that 1 degree precision in the nav exams is such a joke.

[Whopity]

Because everything the Met says is TRUE
Theoretically yes but its actually a Met mans guess, which is less accurate than the variation in the UK, so it matters not whether you use it as True or Mag.