Radio Navigation
Ground-based aids
Know VOR, DME, NDB/ADF, ILS, and their principles. VOR gives radial and bearing; DME gives slant range; NDB gives relative bearing. Know the ILS components: localiser, glide path, markers, and the meaning of the decision altitude. Know the difference between a precision and a non-precision approach.
Area navigation
Understand RNAV, GNSS, and the meaning of RNP and PBN. Know the difference between a GPS and a GNSS, and the meaning of RAIM. Know the meaning of waypoints, fly-by, and fly-over.
Radar and secondary surveillance
Know primary and secondary radar, the meaning of a transponder code, and the difference between mode A, C, and S. Know the meaning of TCAS and its resolution advisory.
Traps
Questions confuse radial with bearing, or DME slant range with ground distance. Another favourite: the meaning of the ILS critical area and the effect of a false glide path.
Worked example
An aircraft at 6,000 ft reads DME 10 NM from a station at sea level. Slant range 10 NM, height 1 NM, so ground distance = √(10² − 1²) ≈ 9.95 NM - a small error at this range, but it grows at close range and high altitude.