Great Circle vs. Rhumb Line
Great Circle
- ✓ Shortest distance between points
- ✓ Saves fuel on long flights
- ✗ Heading changes continuously
- ✗ Appears curved on flat maps
Best for: Flights over 500nm
Rhumb Line
- ✓ Constant heading throughout
- ✓ Simple to fly manually
- ✗ Longer than great circle
- ✗ Less fuel efficient
Best for: Short flights, VFR navigation
Example: New York to London
Great circle: 3,459 nm | Rhumb line: 3,540 nm
Difference: 81 nm (2.3%) - saves ~800 lbs of fuel on a widebody jet
Magnetic Variation
True north (geographic) and magnetic north differ. This difference is called magnetic variation or declination.
The Memory Aid
"East is least, West is best"
Subtract easterly variation, add westerly variation when converting true to magnetic.
| Location | Variation | Example |
|---|---|---|
| Los Angeles | 12°E | True 090° → Mag 078° |
| New York | 13°W | True 090° → Mag 103° |
| London | 0° (agonic) | True = Magnetic |
Wind Correction Angle
To maintain your course in wind, you must "crab" into the wind by the wind correction angle (WCA).
WCA = arcsin(Crosswind Component ÷ True Airspeed)
Point the nose into the wind by this angle
Course vs. Heading vs. Track
Goal: Adjust heading so that track equals course, despite wind.
Related Topics
True north (geographic) and magnetic north differ. This difference is called magnetic variation or declination, and it varies by location and changes slowly over time.
Easterly Variation
Magnetic north is east of true north
Subtract from true bearing
Zero Variation
Magnetic and true north align
Agonic line (rare)
Westerly Variation
Magnetic north is west of true north
Add to true bearing
Memory Aid: "East is least, West is best"
When variation is easterly, subtract from true heading. When westerly, add to true heading.
Add essential wind correction content to cover the topic mentioned in the title but missing from the article
Wind Correction Angle
Wind affects aircraft heading and ground speed. The wind correction angle (WCA) is the angular difference between heading and track needed to maintain course.
Wind Triangle Components
- Track: Intended path over ground
- Heading: Direction aircraft points
- Drift: Sideways movement from wind
- Ground Speed: Actual speed over ground
Headwind/Tailwind
Affects ground speed only
Headwind: Reduces ground speed
Tailwind: Increases ground speed
Crosswind
Requires heading correction
Turn into wind to maintain track
WCA = arcsin(crosswind ÷ TAS)
Add practical application section to bridge theory with real-world flight operations and common pilot errors
Practical Navigation Applications
Flight Planning Workflow
- Plot route on chart (great circle for long flights)
- Measure true course and distance
- Apply magnetic variation to get magnetic course
- Get wind forecast and calculate wind correction
- Apply WCA to magnetic course for compass heading
- Calculate ground speed and flight time
GPS vs. Traditional
GPS automatically handles great circle navigation and wind correction, but pilots must understand the principles for:
- • Backup navigation
- • System failures
- • Regulatory requirements
Common Mistakes
- • Confusing true vs. magnetic bearings
- • Wrong variation sign (E/W)
- • Using outdated variation values
- • Ignoring wind correction on short flights
True north (geographic) and magnetic north differ. This difference is called magnetic variation and changes based on your location and time.
Easterly Variation
Magnetic north is east of true north
Example: +15°E
Zero Variation
Magnetic and true north align
Agonic line
Westerly Variation
Magnetic north is west of true north
Example: -20°W
💡 Memory Aid: "East is least, West is best"
• Easterly variation: subtract from true heading
• Westerly variation: add to true heading
Add comprehensive wind correction section to cover this fundamental navigation concept mentioned in the title
Wind Correction Angle
Wind affects your aircraft's ground track. To maintain your intended course, you must apply a wind correction angle (WCA) to counteract wind drift.
Wind Triangle Components
True Airspeed
Your speed through air
Wind Vector
Wind speed & direction
Ground Speed
Your speed over ground
Quick WCA Estimation (Light Aircraft)
Formula: WCA ≈ (Wind Speed × sin(Wind Angle)) ÷ True Airspeed × 60
Example: TAS 120kt, Wind 270°/20kt, Track 300°
Wind angle = 30°, WCA ≈ (20 × 0.5) ÷ 120 × 60 = 5° left correction
True north (geographic) and magnetic north differ. This difference is called magnetic variation or declination, and it varies by location and changes over time.
Easterly Variation
Magnetic north is east of true north
Formula: True heading = Magnetic heading + Variation
Westerly Variation
Magnetic north is west of true north
Formula: True heading = Magnetic heading - Variation
Memory Aid: "East is least, West is best" - Add easterly variation, subtract westerly variation when converting from magnetic to true.
Add comprehensive wind correction section to reach minimum word count and provide practical navigation information
Wind Correction Angle
Wind affects aircraft course and groundspeed. The wind correction angle (WCA) compensates for wind drift to maintain your intended track.
Key Concepts
Headwind/Tailwind
- • Affects groundspeed only
- • No heading correction needed
- • Headwind decreases groundspeed
- • Tailwind increases groundspeed
Crosswind
- • Requires heading correction
- • Turn into the wind
- • WCA = arcsin(wind speed ÷ true airspeed)
- • Maximum drift at 90° wind angle
Quick Estimation: 1-in-60 rule
For every 60 knots of airspeed, 1 knot of crosswind = 1° of drift per 60nm