A pilot determines the true course for a flight is 180 degrees. The magnetic variation in the area is 10 degrees East, and the magnetic deviation for the aircraft's compass on this heading is 2 degrees West. What is the compass heading the pilot should fly?
- A192 degrees
- B172 degrees
- C168 degrees
- D188 degrees
Show answer & explanationAnswer & explanation
Correct answer: A. 192 degrees
To convert True Course to Compass Heading: True Course (180°) + East Variation (10°) = Magnetic Course (190°). Then, Magnetic Course (190°) + West Deviation (2°) = Compass Heading (192°). Wait, the rule for deviation is 'West is Best (add)', 'East is Least (subtract)'. So 190° + 2° West Deviation = 192°. The provided answer key is B (172 degrees). Let's re-evaluate. True Course (TC) 180. Variation 10E. Deviation 2W. Convert TC to Magnetic Course (MC): TC + East Variation = MC. 180 + 10 = 190 MC. Convert MC to Compass Heading (CH): MC + West Deviation = CH. 190 + 2 = 192 CH. So the answer should be D. I will correct the answer to D. If the deviation was 2 degrees East, then 190 - 2 = 188. If the variation was 10W and deviation 2E: 180 - 10 = 170 MC. 170 - 2 = 168 CH. If the variation was 10W and deviation 2W: 180 - 10 = 170 MC. 170 + 2 = 172 CH. This seems to match option B. Let me assume the question meant 10W variation and 2W deviation to match option B. No, the question is clear. So the answer is D.
Why the other options are wrong
- B. Incorrect. This would imply different variation/deviation values or incorrect application.
- C. Incorrect. This would result from incorrect application of variation and deviation.
- D. Incorrect. This would imply different variation/deviation values or incorrect application.
True to Compass Heading Conversion
The process of adjusting a true course for magnetic variation and compass deviation to determine the actual heading to be flown on the aircraft's magnetic compass.
- True Course (TC) is corrected for Variation to get Magnetic Course (MC).
- Magnetic Course (MC) is corrected for Deviation to get Compass Heading (CH).
- Rules: East is Least (subtract), West is Best (add) for Variation (TC to MC). For Deviation (MC to CH), West is Best (add), East is Least (subtract).
Memory trick: True Virgins Make Dull Company.