Radio Navigation and Area Navigation Systems
Ground-based and satellite navigation
This domain tests understanding of VOR, DME, NDB/ADF, ILS, and area navigation including GNSS and RNAV/RNP. Candidates must know how a VOR radial is defined (magnetic bearing from the station), how to determine which side of a radial the aircraft is on, the cone of confusion overhead a station, and how DME provides slant range rather than ground distance. For ILS, know the localizer and glideslope frequencies, the meaning of the critical and sensitive areas, and the differences between CAT I, II, and III minima.
Traps
Questions often confuse "from" and "to" indications, or ask for the heading to intercept a radial without accounting for wind. Another trap is treating DME distance as ground distance; at high altitude the slant-range error is significant. RNAV questions may test the difference between RNAV and RNP (RNP includes on-board performance monitoring and alerting) and the meaning of "RF" legs. Also expect questions on RAIM availability and the effect of satellite geometry on accuracy.
Worked example
You are on the 090 radial and the CDI shows a full-scale deflection with a "FROM" flag; the OBS is set to 090. A "FROM" indication with the needle centered means you are on the radial. If the needle deflects left, the radial lies to your left; turn left to intercept.
Rule of thumb
VOR radials are magnetic bearings from the station; RNP adds on-board performance monitoring to RNAV.