# Is this the correct sequence of steps to convert from true course to compass heading?

I wanted to confirm my understanding of VFR Flight Planning/Dead Reckoning with relation to heading and course calculation. Is the below correct?

1. Using a plotter, draw a line from departure airport to arrival airport
2. Using the same plotter, get the true course (TC)
3. Using an E6B or similar calculator, calculate the Wind Correction Angle (WCA) which is based on Wind Direction and Speed
4. + or - the WCA to/from the TC and the result will be True Heading (TH)
5. Using the chart, see what the Magnetic Declination is and + or - the value (West is Best [add], East is Least [subtract])
6. The result will be Magnetic Heading (MH)
7. On the day of flight, check the Compass Deviation Card to + or - the deviation from the Magnetic Heading and this will give us the Compass Heading (CH)

# Yep, that's how it's done!

(If you fly the same airplane all the time, one other thing you could do is take a photo of the compass card. That way, you have the deviation already handled and you save a step at the airport.)

• Thanks @steve-v. I do have a question about the compass deviation though. Given the following deviation card, is there are formula to calculate the deviation for a given heading if that heading is not exclusively listed? E.g. our MH is 153, do we just go to the closest number on the card which is 'for 150, steer 148'. What if our MH is 165? Do we go to the deviation of 150 or 180? Dec 19, 2017 at 3:56
• FYI, I asked the above comment on Reddit as well Dec 19, 2017 at 3:59
• @Dan You could use the average of the 150 and 180 numbers.
– Ralph J
Dec 19, 2017 at 9:33

For those interested in a formula to directly compute True heading from True course, here it is:

$$T_H =T_C + \mathrm{arcsin}\left(\frac{W_S}{\mathrm{TAS}}\cdot\mathrm{sin}(W_ D-T_C)\right)\tag{1}$$

where:

• $$T_H$$ is the true heading
• $$T_C$$ is the true course
• $$W_S$$ is the wind speed
• $$W_D$$ is the wind direction (measured with the usual convention of the direction where the wind originates from, not blow to)
• $$\mathrm{TAS}$$ is the true airspeed

Once you've computed $$T_H$$ you can use it to compute ground speed $$G_S$$ as:

$$G_S=\frac{\mathrm{TAS}\cdot\mathrm{sin}(T_H)-W_S\cdot\mathrm{sin}(W_D)}{\mathrm{sin(T_C)}}\tag{2}$$

I know you're asking for magnetic heading but that's extremely complicated to compute mathematically so once you have $$T_H$$ you simply need to look up the magnetic deviation in your sectional chart and add it to the True heading $$T_H$$ (like you already mention in your question)

• Aren't you making it more complicated? The E6B does this for you, and you are simply applying wind before converting to magnetic. Dec 9, 2022 at 17:48
• As far as I'm concerned this is quicker for me. I can do it with a calculator in a matter of seconds. With a flight computer it takes more time (at least it does for me): you have to slide/rotate to find wind. Then mark it with a pencil (a-ha you have to have a pencil too). Then move it to account for TAS and sort of guess where that point falls at. Then erase the dot you made with the pencil (a-ha you have to have an eraser) . With a calculator is just one formula. Hit "=". There you have it :)
– fab
Dec 9, 2022 at 18:29
• Anyway, this is just for reference, in case someone needs a precise calculation. I understand most people will favor a E6B.
– fab
Dec 9, 2022 at 18:31