Radio Navigation
Radio Navigation tests how ground and satellite aids present information in the cockpit, what their errors are, and how to turn a bearing or a deviation into a usable position or approach path.
VOR and DME
A VOR radial is a line measured from the station outwards: you fly outbound on the radial matching your track from the station. With the OBS set to the desired radial, the CDI centres when you are on it, and the TO/FROM flag tells you whether the selected course leads to or away from the station. Reverse sensing occurs when you fly a course opposite to the OBS setting. DME gives slant range, which always exceeds ground distance and becomes significantly wrong at high altitude close to the station.
NDB and ADF
The ADF needle points to the station (relative bearing); QDM is the magnetic bearing to the station, QDR the bearing from it, QTE the true bearing. Known errors are night effect, coastal refraction, thunderstorm static, mountain effect and quadrantal error.
ILS, GNSS and surveillance
ILS combines a localiser (90 Hz/150 Hz modulation for left/right) and a glide path, usually 3°, plus markers or DME for range. Typical minima are CAT I at about 200 ft and 550 m RVR; CAT II and III need specific approvals. GNSS depends on satellite geometry and RAIM; SBAS and GBAS improve integrity. Transponders use modes A/C/S with assigned squawks; TCAS and EGPWS are independent safety nets.
Worked example
On a 3.0° glide path with a 50 ft threshold crossing height, one nautical mile from the threshold the nominal height is 6,076 × tan 3° ≈ 318 ft per NM. At 4 NM DME the aircraft should be at 50 + (4 × 318) ≈ 1,320 ft.
Traps that cost marks
Confusing a radial with a bearing; ignoring the TO/FROM flag; treating DME as ground distance; and forgetting the ADF errors that appear at night or near coastlines.
Communications (VFR and IFR)
Communications tests standard radiotelephony: the correct phraseology, what must be read back, how distress and urgency calls are made, and how to handle lost communications under VFR and IFR.
Standard phraseology
Use the ICAO phonetic alphabet and standard words precisely: ROGER means received; WILCO means received and will comply; AFFIRM is yes; STANDBY means wait, I will call you; CLEARED is used only for clearances; and the word "take-off" is used only when issuing an actual take-off clearance - otherwise say "departure". Transmit the full callsign on the first contact, then the abbreviated form.
Readback requirements
Safety-related items must be read back: route clearances, altitudes and levels, headings, speeds, frequencies, SSR codes, runway-in-use, holding points and altimeter settings. Readback of a clearance is not optional politeness - it is the loop that catches errors.
Distress and urgency
Distress calls start with MAYDAY (three times) and are used when in grave and imminent danger; urgency calls use PAN PAN (three times) for a situation that is not immediately life-threatening. Both are followed by callsign, nature of the problem, intentions, position, level, and any other useful information.
Lost communications
Under IFR, a radio failure follows the filed or last acknowledged route and levels, with the appropriate timekeeping; the transponder is set to 7600. Under VFR you remain in VMC, land at the nearest suitable aerodrome and notify ATC. Squawk 7700 for a general emergency and 7500 for unlawful interference.
Worked example
Tower: "November five four two, cleared to Accra via the filed route, climb flight level one five zero, squawk four five two one." The readback must include the clearance limit (Accra), the route, the level (FL150) and the squawk (4521). Answering "Roger, November five four two" leaves ATC unsure whether you have accepted the level or the code, and is treated as an incomplete readback.
Traps that cost marks
Using ROGER for a clearance that requires readback; omitting the altimeter setting or squawk; using "take-off" in a ground or departure clearance; and confusing MAYDAY with PAN PAN.