On the next question - Question 6 Page 3.8 - using the same mechanism and a 9 deg right WCA I get a MH of 172 deg and a GS of 115.

The answers however in the book are saying MH should be 187 deg mag and 110kt. That is 15 degrees magnetic off and 5 knots GS off.

Think I got it - my mistake was based on my workings in step 3. Still curious about the US vs Australian thing though, as it relates to flight computers and planning.

In terms of the expression "East is Least" (subtract) and "West is Best" (add)that is in reference to the original TRUE course. So the Magnetic course has already taken this into account.

For example, if the MAGNETIC Course was 300 deg for example, and the variation was 15 deg EAST, you would NOT subtract a FURTHER 15 degrees from 300 degrees thinking east is least, since this has ALREADY been subtracted (with reference to TRUE ALREADY being 315 deg). So if you get a magnetic course, you need to use reverse psychology and ADD East and SUBTRACT West to get your original SOURCE true heading.

FYI it also appears that the answer from Q10 is not there..

Brook

You will find that if you work the exercises using all directions as degrees true, i.e. wind direction as true and course [which we call flight planned track] as true, then you will get a heading as a true heading. Since directions on flight plans are usually written as magnetic, you would need to convert the answer to a magnetic heading by applying the local variation.

The other option is to convert everything to magnetic before you begin - wind as magnetic and flight planned track as magnetic. [This is the preferred method in most Australian flying schools]. You will then get a magnetic heading. It will be the same heading. A rule often used is 'any direction written on paper is always magnetic'. One good reason for this is that all directions on instrument approach charts and on ERC and VTC charts are always magnetic. Magnetic is the 'work-bench language' of the pilot'

So when you read the wind off the area forecast, you apply the local variation to make it magnetic before you write it down. When you measure the flight planned track [or course] off the map, you keep it in your head and apply the variation to make it magnetic before you write it down. When you get into the cockpit, you take the magnetic heading off the flight plan and apply the deviation from the compass deviation card [also mentally] to decide the compass heading to fly.

The ground speed in each case will be the same.

Thanks Bob - interesting. At the UK and US flight schools I have been involved with they both went off anything written was true, anything spoken was magnetic, and that was a big point they drummed into you.

The only issues I can see here (why I got confused at the Aussie Schools as well having done both) really comes from the use of the E6B and also the use of written material.

Interesting about Aussie instrument approach charts being WRITTEN in MAGNETIC. Now it makes sense!

So for you then as you interpret the E6B - would you just fill in any of the TC and TH below with Magnetic? (I wonder why this was not made a worldwide standard by ICAO or JAA?)

TC (True Course) -L or + R WCA (Wind Correction Angle) = TH (True Heading) -E or +W VAR (Magnetic Variation)=MH (Magnetic Heading) -E or +W DEV (Compass Deviation)= CH (Compass Heading

Australia is a member of ICAO, all ICAO instrument approach charts are written in magnetic. If you check the Jepps charts and maps, they are all in magnetic.

So Bob what do we do with the computer formula (below) - its written on the working area of the E6B, and typically expects you to pencil in the variables down the bottom of the computer. Do we simply change the True Course and True Heading to Magnetic? Will that work?

TC (True Course) -L or + R WCA (Wind Correction Angle) = TH (True Heading) -E or +W VAR (Magnetic Variation)=MH (Magnetic Heading) -E or +W DEV (Compass Deviation)= CH (Compass Heading)

I haven't yet done my instrument rating, but all of the sectionals /VNC's, WAC and VTC's are true not magnetic in both countries, so its interesting that when switching to instrument it also switches to Magnetic.

To me from your statements it seems when time is of the essence, magnetic is better, in terms of less time to recompute.

If you have a look at the FAA or King Schools Flight planning sheets, they both have spaces for TRUE course instead of magnetic, and then get you to apply the variation on this. Seems like a fairly pointless extra step if its easier just to do it all in Magnetic?

The CASA pre flight planning (VFR) sheets omit this True course area. I can scan a copy of each if it helps. It mainly just for the computer I am trying to make it consistent so if in the air I can feed in the variables as per the computers requirement.

Perhaps it would be better for you if you stick with working in true as the formula says. It really doesn't make any difference to the answer.

I have never heard of a VTC or ERC in any country that publishes tracks as true directions. See attached. All OMNI radials are magnetic and all GPS bearings are magnetic in every country. It seems you are asking for trouble if you publish tracks on the chart as true.

[attachment=293]ercmagnetic.gif[/attachment]

[attachment=294]VTC-magnetic.gif[/attachment]

Thanks so much for that Bob, sorry I haven't been near a computer to reply sooner.

I have tried both the US calculations and the Australian Magnetic Calcs on my E6B and blow me down, the Aussie way is quicker and easier operationally.

Interesting. Intead of 7 Steps (USA) there are only 3 steps (Australia - BT) to achieve the same outcome. As soon as I'm near the scanner I will send over the VFR US stuff and dial of the computer by way of comparison.

I wonder why the Yanks Do convert to True all the time in the formula?

One thing I noticed - The yanks are bigger on Wind Correction Angle, Aussies on Drift which appears to be the same thing.

Hey, sorry to interrupt the conversation, but Bob, what program do you use to draw on the charts and make the diagrams for the book and stuff? If you don't mind me asking.

I was just about to ask the same question as Aviatordan..

Hi Bob,

Here is some pages directly from the US Department of Transportation FAA Pilots Handbook of Aeronautical Knowledge (FAA-H-8083-25A).

I have underlined the key points I learnt from and included a copy of the US Flight Planning Guide. In summary they appear to suggest that Magnetic headings are not accurate enough on longer, faster, or more magnetically varying flights, and therefore should be calculated in true, as well as headings.

I have also included a copy of front and back of the E6B that I use, which now makes perfect sense. In terms of approach charts for airports it makes sense to use magnetic due to the proximity of the airport, but on the cross country flights it appears that is where True Course is more relevant. See if you can see where I am coming from, I would be really interested in your educated opinion, on the forum or PM.

It relates to where I take the flight component as well, as I may well do the CPL flight rating at Flight Safety in the US, or Oxford or Brisol if I go JAA, but I'm not sure yet. I just want the best foundation I can get my hands on, and I've seen a few Uni's try to have a go as well 😉

Hi Bob,

Back when I first asked you I also (out of sheer desperation that was doing my head in) asked the question of a 74 year old Veteran Pilot ex Major Global Airlines (lastly Qantas) with 33,000 hours, 50+ Type Ratings and 5 ATP(L) of which I have personally sighted, and this is what he said to me (I only just got the email): (I'll call him to Clarify, but it tends to indicate the necessity of True Course on planning LONGER flights: (does this make any more sense to what I was suggesting or am I just being Anal Retentive (Go on - just be honest 🙂 It's just I struggled with Nav to start with and having worked with Computers and Data Processing equipment for 20 odd years in Enterprise systems, I have an interest in getting the underpinning fundamentals spot on.

Here goes:

Brook.

I could carry on With some paragraphs to answer your question and still not
be exactly sure that I have answered it to your satisfaction.

However, a brief summary is that a track measured on a WAC chart will be in
T and needs variation applied to be M. Also, area winds are T but
Terminal winds are M as are tracts on terminal charts. I won't elaborate
further now but give a call if you have any difficulty. Once you get it
right you won't have any further problems.

All the best.

JG

That's a good point for long flights in high latitudes. I can see that it might be an advantage to have the true track available when there is going to be large and rapid changes in magnetic variation enroute. It's even possible on a long flight at high latitudes to have variation changes from East to West variation.

Thank goodness you're in Australia now - you can relax at bit!!

Bob

Hey Brook,

I may not be able to answer your question but I'll try to share some insight =). I'm not sure where you are, geographically, so forgive me if I spout some information you already know!

In my experience, albeit limited, I've found it's always best to do things in magnetic. And I guess the point I have to stress is that I've only done flying training in Australia, so I can't say anything for other countries and their magnetic variations.

When I plan a flight I do everything in magnetic, just because it makes it easier in flight. I use the E6B to find wind correction angles etc, all in magnetic. The E6B says to do it in true, however, I just pretend that in stead of the word "true" it says magnetic. That was something that really confused me to start off with.

As far as flying on the true bearing, that really depends where you are (in Aus). I mean, where I am, on the East Coast, the magnetic variation is 12° E so it would be silly to use the true because you'd be pretty far off your destination (depending on the length of flight). Around here, I use the 12° E for flights of any length, I mean it's 70nm West before you hit the next isogonal and even then it only changes by 1/2 degree.
However, just east of Perth, the variation gets to 0° so around that area true = magnetic, so it's perfectly fine to use true.

I guess it just depends on where you are!

I hope that can be of some help =).