Read the radial before the needle
Select an inbound course from a known VOR radial, then interpret the CDI and TO/FROM together.
What you’ll learn
- Separate radial from heading.
- Relate OBS, CDI and TO/FROM to one selected course.
- Choose an inbound course using a consistent magnetic reference.
A radial describes position
Radial 090° extends eastwards from the station. An aircraft on it is east of the station, regardless of where its nose points. Facing the station does not turn radial 090° into radial 270°.
This lesson uses one magnetic reference for the radial, OBS and course. Earlier wind exercises used true directions. Keep those references separate rather than transferring angles blindly.
A radial runs from the station to the aircraft’s position.
Choose a direction along the line
The OBS selects a course direction. On radial 090°, OBS 090° gives a centred CDI with FROM; OBS 270° gives a centred CDI with TO. These reciprocal selections describe the same line in opposite directions.
With the CDI centred, TO means the selected course leads towards the station; FROM means it leads away. The flags do not establish actual movement. An aircraft can fly away while the instrument still shows TO.
Read the selected course, CDI and TO/FROM together.
Look along the selected course
The CDI shows displacement from the selected course line. It is not a pointer aimed at the transmitter. Imagine looking in the OBS direction before interpreting left and right.
With OBS 270°, you look west: north is on your right. If the aircraft is south of the east-west course line, the CDI deflects right towards that line. This is normal sensing. Flying opposite to the selected course reverses the simple steering interpretation.
Left and right belong to the selected course direction.
Change selection without changing position
Start with radial 090° at 5 NM and OBS 090°: centred FROM. Keep that radial and select the reciprocal course. Check for both a centred CDI and TO. You have changed the selection, not the aircraft’s position.
The scenario supplies the 5 NM distance. VOR azimuth alone does not measure range; that needs another suitable source, such as DME.
Changing OBS changes the chosen course; changing position changes the radial.
Select the inbound course
Keep radial 090° at 5 NM. Adjust OBS, observe the CDI and TO/FROM, then check your setup. The radial control changes position, not heading.
TBR · 5 NM · The VOR model uses one magnetic reference. The aircraft’s heading does not set its radial.
Type a value or use the slider. Arrow keys make small changes.
Select an inbound course giving centred TO on radial 090°.
Show a hint
Choose the reciprocal direction towards the station.
Explore the controls, then check your setup against the task.
Inbound from 5 NM east of the VOR
- Radial 090° places the aircraft east of the station.
- OBS 090° initially gives centred FROM.
- Calculate the reciprocal: 090° + 180° = 270°.
- Select OBS 270°, keeping radial 090°: centred TO.
Inbound course 270° on radial 090°. All angles use the same magnetic reference.
Check your understanding
- Radials describe position; heading describes where the nose points.
- Reciprocal OBS settings can keep the CDI centred while switching FROM and TO.
- Interpret the CDI along the selected course. Keep references consistent; a radial alone does not give distance.
Complete lesson
Solve the interactive exercise and all four checks to complete this lesson.
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Progress saved on this browserSources & syllabus
AMC1 FCL.210; FCL.215 — Navigation 9.2: radio navigation and radio aids, including VOR.
- EASA — Easy Access Rules for Aircrew, October 2026 ↗AMC1 FCL.210; FCL.215 — PPL(A) Navigation syllabus, Radio Navigation and radio aids.
- FAA — Pilot’s Handbook of Aeronautical Knowledge, FAA-H-8083-25C ↗Chapter 16, Navigation: VOR radials, OBS, course-deviation indications and TO/FROM. Used for universal instrument principles, not European operating procedures.
- FAA — Aeronautical Information Manual ↗1-1-3 VOR and 1-1-7 DME: bearing information, station identification and the distinction between VOR azimuth and separate distance measurement.
These references support the syllabus scope and the navigation principles taught here. The exercises and explanations are original Trimbrief material.
Simplified, steady-wind learning model; no live weather or operational navigation data.
Content edition: 2 November 2026