VOR navigation is a radio navigation system that helps pilots find their position and follow a chosen course using signals from a ground station. VOR stands for Very High Frequency Omnidirectional Range, and it works by sending out directional information in all compass directions. Each direction from the station is called a radial, like a spoke from the center of a wheel.
This matters because VOR lets pilots navigate accurately even when roads, landmarks, or visibility are poor.
A VOR station defines 360 radials, one for each degree on a compass, measured clockwise from magnetic north. An aircraft receiver compares signals from the station and shows the pilot whether the airplane is left or right of the selected course. The pilot can track outbound on a radial away from the station or inbound toward the station on the reciprocal course.
In the cockpit, an Omni Bearing Selector and Course Deviation Indicator help the pilot choose and follow the desired path.
Key Facts
- A VOR radial is a magnetic bearing measured outward from a VOR station.
- There are 360 VOR radials, labeled 000 through 359 degrees.
- The reciprocal course differs by 180 degrees: reciprocal = radial + 180 degrees if radial < 180, or radial - 180 degrees if radial >= 180.
- To fly outbound on the 090 radial, the aircraft tracks east away from the station.
- To fly inbound to the station on the 090 radial, the aircraft normally flies a 270 degree course.
- VOR signals use VHF radio frequencies, typically from 108.00 MHz to 117.95 MHz.
Vocabulary
- VOR
- A radio navigation system that lets aircraft determine direction to or from a ground station.
- Radial
- A magnetic direction extending outward from a VOR station, measured in degrees from magnetic north.
- Course
- The intended direction of travel of an aircraft over the ground.
- CDI
- A Course Deviation Indicator shows whether the aircraft is left or right of the selected VOR course.
- Reciprocal
- The opposite direction on a compass, exactly 180 degrees from the original direction.
Common Mistakes to Avoid
- Confusing a radial with a heading. A radial is a line from the station, while heading is the direction the aircraft nose points.
- Forgetting that radials extend outward from the station. If you are flying toward the station on a radial, your course is usually the reciprocal direction.
- Adding 180 degrees without wrapping around 360. For example, the reciprocal of 240 degrees is 060 degrees, not 420 degrees.
- Assuming the CDI shows distance from the station. The CDI shows left or right course deviation, while a separate DME system may show distance.
Practice Questions
- 1 An aircraft is tracking outbound on the 135 radial from a VOR. What general compass direction is it flying, and what is the reciprocal inbound course?
- 2 A pilot wants to fly inbound to a VOR while located on the 300 radial. What course should the pilot select to fly directly toward the station?
- 3 Explain why an aircraft flying toward a VOR on the 090 radial does not use a 090 degree course to reach the station.