Radio Navigation
Ground and satellite aids
Candidates must understand the principles of VOR, DME, NDB/ADF, ILS, radar and GNSS. Learn the meaning of radial, bearing, track and the cone of confusion, and how to intercept and track a radial. Understand the ILS components (localiser, glideslope, markers), the meaning of the decision altitude and the missed approach point, and the limitations of each aid. Also learn the principles of RNAV, RNP and the use of waypoints.
Traps in questions
A frequent trap is confusing a VOR radial with the aircraft's heading, or forgetting that the CDI shows the aircraft's position relative to the selected course, not the aircraft's track. Another is assuming that an ILS glideslope is always usable to the runway - it has a published minimum. Questions also test the difference between a localiser and a glideslope, and the effect of the cone of confusion.
Worked example
"You are on the 090 radial, tracking inbound to the station. What heading do you fly?" Answer: to fly toward the station on the 090 radial, fly approximately 270° (allowing for wind). Rule of thumb: the radial is from the station; your heading is where you point.
Key points
- A radial is measured from the station, not from the aircraft.
- The CDI shows position relative to the selected course.
- Know the ILS components and the decision altitude.
- Understand the cone of confusion.
- Know the limitations of each navigation aid.