FAA Sport Pilot Airplane (SPA)Airspace and NavigationMedium
An aircraft's VOR receiver has the OBS set to 270°, and the CDI is centered with a TO indication. On which radial from the VOR is the aircraft located?
- A090° radial
- B360° radial
- C270° radial
- D180° radial
Show answer & explanationAnswer & explanation
Correct answer: A. 090° radial
With a centered CDI and a TO indication, the OBS setting represents the course TO the station, which is 270°. The radial the aircraft is on is the reciprocal of that course, since a radial is always defined as a course FROM the station: 270° − 180° = 090°.
Why the other options are wrong
- B. 360° does not correspond to the reciprocal of 270°.
- C. 270° is the course TO the station, not the radial FROM it.
- D. 180° is not related to either the course or its reciprocal in this scenario.
VOR Radial Identification (TO/FROM)
A radial is always a magnetic course measured FROM the VOR station outward; a TO indication means the OBS setting is a course flying toward the station, so the radial is the reciprocal of that setting.
- Radial = course FROM the station
- TO indication + OBS = course toward the station
- Radial = OBS setting ± 180° when indication is TO
Memory trick: 'TO means you're headed toward home, so you're standing on the opposite radial.'