11.1 Magnetic Course
A number of FAA knowledge test questions ask you to determine the magnetic course for a specific flight.
Magnetic course (MC), is the True Course (TC) adjusted for magnetic variation. Magnetic course is the course that would take you directly from origin to destination if there was no wind along the route of flight.
Determine the True Course (TC) by placing the straight edge of a navigational plotter or protractor along the route, with the hole in the plotter on the intersection of the route and a meridian, or line of longitude (the vertical line with small tick-marks).
- The TC is measured by the numbers on the protractor portion of the plotter (semi-circle) at the meridian.
- Note that up to four numbers (90° apart) are provided on the plotter. You must determine which is the direction of the flight, using a common sense approximation of your direction.
Alternatively, you can use a line of latitude (horizontal line with small tick-marks) if your course is in a north or south direction.
- This is why there are four numbers on the plotter. You may be using either a meridian or line of latitude to measure your course and be going in either direction along the course line.
To determine the Magnetic Course (MC) for your route of flight, adjusted the True Course (TC) by adding or subtracting the charted magnetic variation.
- On sectional charts, a long dashed line provides the number of degrees of magnetic variation (angle between true north and magnetic north).
The variation is either East or West and is signified by "E" or "W," for example, 3°E or 5°W.
- If the variation is East, subtract the variation from the TC; if the variation is West, add the variation to the TC.
Use this saying as a memory aid: "East is least. West is best".
If you determine your course using the compass rose around a VOR, the compass rose is already adjusted for the magnetic variation, so your course is already a magnetic course and no adjustment is needed from TC to MC. The compass rose surrounds VORs and has every 30° labeled, as well as tick marks for every 5°.
Remember to use the reciprocal heading of radials when flying TO the VOR. For example, if your course is toward an airport is on the 090° radial, the your heading to the airport, which is your MC, is 270°, not 090°.
Question 1: (Refer to figure 27.) Determine the magnetic course from Breckheimer (Pvt) Airport (area 1) to Jamestown Airport (area 4).
Question 2: (Refer to figure 21.) Determine the magnetic course from First Flight Airport (area 5) to Hampton Roads Airport (area 2).
Question 3: (Refer to figure 22.) What course should be selected on the omnibearing selector (OBS) to make a direct flight from Mercer County Regional Airport (area 3) to the Minot VORTAC (area 1) with a TO indication?
Question 4: (Refer to figure 24.) On what course should the VOR receiver (OBS) be set to navigate direct from Hampton Varnville Airport (area 1) to Savannah VORTAC (area 3)?
Question 5: (Refer to figure 25.) Determine the magnetic course from Airpark East Airport (area 1) to Winnsboro Airport (area 2). Magnetic variation is 6°30'E.
Question 6: (Refer to figure 25.) On what course should the VOR receiver (OBS) be set in order to navigate direct from Majors Airport (area 1) to Quitman VORTAC (area 2)?
11.2 Magnetic Heading
Magnetic Heading (MH) is Magnetic Course (MC) adjusted for wind correction angle. Remember, magnetic heading would keep you on your desired course only if there is absolutely no wind. Your wind correction angle is the angle that you must "crab" into the wind in order to track along your magnetic heading.
Determine your wind correction angle using the wind side of the E6-B, and a given :
- Align the magnetic wind direction on the inner scale under the true index at the top of the computer.
- Wind directions are normally given in relation to true north, not magnetic. So, you must adjust the wind direction from true to magnetic by adding or subtracting magnetic variation.
- Find the magnetic variation on the navigation chart. Just as you did above for course corrections, add westerly variation and subtract easterly variation.
- For example, if given a wind of 350° and a 10°E variation, the magnetic direction of the wind is 340° (350° – 10°).
- Slide the grid through the computer until the grommet (the hole in the center) is on the 100-kt. wind line. Measure up the vertical line the amount of wind speed in knots and put a pencil mark on the plastic.
- Rotate the inner scale so that the MC lies under the true index.
- Slide the grid so that your pencil dot is superimposed over the true airspeed (TAS). The location of the grommet will indicate the groundspeed. This is needed for time en route calculations.
- The pencil mark will indicate the wind correction angle (WCA). If the marks is on the left, it is a negative wind correction. If it is on the right, it is a positive wind correction.
To determine your MH, add or subtract your WCA to or from your MC
- Add the number of WCA degrees if the pencil mark is on the right of the centerline
- Subtract the number of WCA degrees if it is on the left.
Converting your True Course (TC) to Magnetic Course (MC), and converting your winds to from true to magnetic means that you do not have to convert your final answer to magnetic since both components (course and winds) have already been adjusted to magnetic before you began using the wind side of your E6-B. Many courses for cross-country flights are to or from VORs, which allow you to use the compass rose to determine MC directly, allowing you to skip the plotter routine for determining TC and adjusting it to MC. Just remember, the compass rose around VORs is already adjusted to magnetic north.
Question 1: (Refer to figure 22.) Determine the magnetic heading for a flight from Mercer County Regional Airport (area 3) to Minot International (area 1). The wind is from 330° at 25 knots, the true airspeed is 100 knots, and the magnetic variation is 10°E.
Question 2: (Refer to figure 23.) What is the magnetic heading for a flight from Priest River Airport (area 1) to Shoshone County Airport (area 3)? The wind is from 030° at 12 knots and the true airspeed is 95 knots.
Question 3: (Refer to figure 23.) Determine the magnetic heading for a flight from St. Maries Airport (area 4) to Priest River Airport (area 1). The wind is from 340° at 10 knots and the true airspeed is 90 knots.
Question 4: (Refer to figure 23.) Determine the magnetic heading for a flight from Sandpoint Airport (area 1) to St. Maries Airport (area 4). The wind is from 215° at 25 knots and the true airspeed is 125 knots.
Question 5: (Refer to figure 24.) Determine the magnetic heading for a flight from Allendale County Airport (area 1) to Claxton-Evans County Airport (area 2). The wind is from 090° at 16 knots, and the true airspeed is 90 knots.
Question 6: (Refer to figure 26.) Determine the magnetic heading for a flight from Fort Worth Meacham (area 4) to Denton Muni (area 1). The wind is from 330° at 25 knots, the true airspeed is 110 knots, and the magnetic variation is 7°E.
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