Radio Navigation
This domain tests your ability to use ground-based and satellite navigation to fix position, track, and fly approaches, and to recognise the limitations of each sensor.
VOR, DME and NDB
A VOR gives a magnetic radial, a line of position; the CDI or HSI shows deviation and TO/FROM. VOR is line-of-sight and unusable in the cone of confusion overhead. DME measures slant range, so it over-reads close in and at high altitude. NDB/ADF uses relative bearings; it suffers from thunderstorm interference, night effect, terrain and coastal refraction, and is less accurate than VOR.
ILS
An ILS provides localizer and glideslope guidance, typically on a 3° path, with markers or DME for range. Protect the critical and sensitive areas when ILS guidance is in use, and discontinue the approach if flags appear or deviation is excessive.
GNSS and PBN
RNAV and RNP rely on GNSS; RAIM prediction is required where fault detection is needed. Know fly-by and fly-over waypoints, RNP AR requirements, baro-VNAV temperature limits, and plan for GPS jamming or outage.
Worked example
At 10,000 ft, DME reads 10.1 NM. Height is 1.64 NM, so ground distance is the square root of (10.1² − 1.64²), about 10.0 NM. The 0.1 NM error is small here but grows at close range and high altitude; at 40 NM it is negligible.
Marks-losing traps
Confusing radials with bearings; reversing TO/FROM; treating DME as ground distance close in; forgetting NDB errors; launching an RNP approach without RAIM or temperature checks.