Navigation (General Navigation, Radio Navigation)
What this paper tests
Navigation combines general navigation - the Earth, magnetism, dead reckoning, wind triangles, map reading - with radio navigation (NDB/ADF, VOR, DME, ILS, GNSS). Expect conversions between true, magnetic and compass headings and simple in-flight corrections.
General navigation
- One minute of latitude equals one nautical mile; latitude and longitude fix position; a rhumb line keeps a constant track, a great circle is the shortest distance.
- Conversions: true to magnetic applies variation ('variation east, magnetic least'); magnetic to compass applies deviation from the deviation card.
- The wind triangle links heading and TAS, track and ground speed, and wind; drift is the angle between heading and track.
- The 1-in-60 rule: 1 nm off track in 60 nm equals 1°, so degrees = (distance off track × 60) ÷ distance flown.
Radio navigation
- NDB/ADF: relative bearing from the needle plus magnetic heading gives the magnetic bearing to the station (QDM); the tail of the needle gives the QDR.
- VOR: radials are magnetic and radiate from the station; the OBS selects the radial, the CDI centres on track, and TO/FROM shows whether you track to or from the beacon. Full-scale CDI deflection represents about 10°.
- DME gives slant range in nautical miles - accurate at long range, increasingly in error directly overhead.
- ILS: the localizer gives azimuth, the glideslope a nominal 3° path, markers and DME give range; localizer sensitivity increases near the threshold.
- GNSS: confirm RAIM and the integrity of the approach; a handheld GPS is a supplemental aid, not a substitute for pilotage.
Worked example
You are 30 nm along a 60 nm leg and 2 nm right of track. Track error = (2 × 60) ÷ 30 = 4°. With 30 nm to run the closing angle is also (2 × 60) ÷ 30 = 4°, so turn left 8° to arrive overhead. If instead 40 nm were gone with 20 nm to run, the correction would be 3° + 6° = 9°.
Traps that cost marks
- Applying variation or deviation to VOR radials, which are already magnetic.
- Mixing relative bearings and magnetic bearings from an ADF.
- Twisting the OBS instead of turning the aircraft when correcting a CDI deflection.
- Using TAS where ground speed is required for ETA and fuel.