FAA Aircraft Dispatcher (ADX)Flight Planning and PerformanceHard
A dispatcher is planning an overwater flight between two points located at the same latitude but separated by a large difference in longitude, away from the equator. Which statement correctly compares the great circle route to the rhumb line route?
- AThe great circle route is shorter but requires a continuously changing true course as the flight progresses.
- BThe great circle route is longer because it curves toward the pole, increasing total distance flown.
- CBoth routes are identical in distance and course since the latitude is constant along the entire flight.
- DThe rhumb line is shorter because it maintains a constant true course throughout the flight.
Show answer & explanationAnswer & explanation
Correct answer: A. The great circle route is shorter but requires a continuously changing true course as the flight progresses.
A great circle is the shortest distance between two points on a sphere (except along the equator or a common meridian), but it requires a continuously changing true course because it crosses meridians at varying angles, unlike the rhumb line, which holds a constant course but is a longer path.
Why the other options are wrong
- B. Curving toward the pole is what makes the great circle shorter, not longer, at higher latitudes.
- C. Constant latitude does not make the routes identical; the great circle still curves toward the pole and is shorter.
- D. The rhumb line maintains constant course but is a longer distance, not shorter.
Great Circle vs Rhumb Line
A great circle is the shortest path between two points on a sphere with a constantly changing true course; a rhumb line holds a constant course but is longer except along the equator or a meridian.
- Great circle = shortest distance, changing true course
- Rhumb line = constant true course, longer distance (except equator/meridian)
- Used extensively in long-range and overwater flight planning
Memory trick: Great circle = the shortcut that keeps turning; rhumb line = the straight-course long way.