Given:
WCA: -012°
TH: 125°
MC: 139°
DEV: 002°E
What are: TC, MH and CH?
For this type of questions, the comprehension of some basic definitions is required:
- Heading is the angle from the aircraft's fore and aft axis to the north datum. True north in case of a true heading, magnetic north in the case of a magnetic heading.
- Track or Course is the aircraft's path over the ground. The path we wish to follow is called Required Track and the path we actually end up taking is called Track Made Good.
- Drift is the angle between the aircraft's heading and the track made good. It is called left drift (-) when the track made good is less than the heading and starboard (+) when tha track is greater than the heading. Drift always goes from heading to track and is due to the wind.
- Wind Correction Angle (WCA) is the correction to be made on the heading, because of the wind, so as to follow the desired track. WCA is equal to the drift, but has opposite sign. For example, when dift is 3°Right(+), then WCA is 3°Left(-). WCA goes from track to heading.
- Variation is the difference between true and magnetic heading or between true and magnetic track. Remember the rhyme: Variation East(+), Magnetic Least - Variation West(-), Magnetic Best.
- Deviation is the difference between magnetic and compass heading or between magnetic and compass track. Remember the rhyme: Deviation East(+), Compass Least - Deviation West(-), Compass Best.
For this question, proceed with the following manner:
- WCA is -012° and goes from track to heading. So, MH = MC + WCA = 139° - 012° = 127°.
- WCA is -012°, so drift is +012°.
- Drift goes from heading to course. So, TC = TH + Drift = 125° + 12° = 137°.
- Deviation is 002°E. Deviation East(+), Compass Least, so CH = MH - Deviation = 127° - 002° = 125°.
NOTES:
- TC: True Course
- TH: True heading
- MC: Magnetic Course
- MH: Magnetic Heading
- CH: Compass Heading
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This question has appeared on the real examination, you can find the related countries below.
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Austro Control