Navigation and Radio Navigation Aids
This domain covers dead reckoning, pilotage, and the ground-based and satellite systems used in instrument flight. Candidates must understand VOR radials and the CDI: the course selector sets the desired course, the needle shows deviation, and TO/FROM indicates whether the selected course leads to or from the station. Know that a VOR radial is a magnetic bearing from the station, so an aircraft on the 090° radial is east of the station flying a 270° course inbound. Understand NDB and ADF relative bearing, DME slant-range error, ILS localizer and glideslope sensitivity, and how GPS/RNAV waypoints and RAIM affect approach legality.
Common traps involve reverse sensing: if the selected course is more than 90° from the aircraft heading, the needle deflects opposite to the turn needed. Another trap is confusing the localizer with the glideslope-localizer is lateral, glideslope vertical-and misunderstanding that a full-scale localizer deflection at the runway threshold is only a few hundred feet. Questions also probe magnetic versus true north and the effect of magnetic variation on course calculations.
Rule of thumb: to intercept a radial, turn to a heading of about 30° to the radial and track inbound; then correct. Worked example: cleared to intercept the 180° radial inbound. The inbound course is 360°. Turning to a heading of 330° gives a 30° intercept angle; when the CDI centers with a TO indication, turn to 360° and track.