Brunei DCA CPL(A) Radio Navigation cheat sheet

Frequency and wavelength: λ (m) = 300 / f (MHz). Doubling frequency halves wavelength; VHF/UHF navaids use line-of-sight geometry because of this.

Speed of all radio waves in free space is c ≈ 3 × 10^8 m/s; in atmosphere slightly slower, so computed DME/radar ranges are marginally conservative.

Ionospheric skywave affects HF (3–30 MHz) mainly; VHF (108–137 MHz) and UHF (960–1215 MHz) navaids normally propagate by direct space wave, so range is limited by horizon.

Radio horizon ≈ 1.23 × √(height in feet) NM, or 4.12 × √(height in metres) km; add transmitter and receiver horizons for total usable range.

Refraction bends VHF/UHF waves slightly around the Earth, extending practical line-of-sight by roughly 15% above geometric horizon under standard atmosphere.

Polarisation: VOR and ILS localiser radiate horizontally polarised; ILS glidepath, DME and marker beacons use vertical polarisation. Mismatched aircraft antenna degrades reception.

Modulation types: AM (VOR, NDB, ILS, VHF voice), pulse (DME, SSR, radar), FM (some satellite links). Sideband and modulation depth determine demodulated audio quality.

Interference mechanisms: co-channel and adjacent-channel interference, cross-modulation, multipath (reflections), and precipitation static. Signal-to-noise ratio governs usable range.

VOR frequency band 108.0–117.95 MHz, 50 kHz spacing; frequencies 108.0–111.85 ending in odd tenths are shared with ILS localisers, so verify the audio ident before use.

VOR radial = magnetic bearing from the station to the aircraft. The OBS/CDI shows the selected radial; TO/FROM flag depends on aircraft position relative to the station.

CDI deflection: full-scale ≈ ±10°; each dot ≈ 2° on a 5-dot display. Fly toward the needle to intercept, then track with reference to the selected radial.

Cone of confusion: directly overhead the VOR the CDI becomes erratic; within about 40° of the station the indication is unreliable for tracking, so use other guidance.

Line-of-sight limitation: VOR usable range ≈ 1.23 × √(altitude in feet) NM, so low-level flight gives short reception; terrain and buildings cause scalloping and bending.

DME measures slant range (not ground distance) in nautical miles; error is largest directly overhead, where slant range exceeds ground distance by the aircraft altitude.

DME frequency is paired automatically with VOR/ILS (UHF 962–1213 MHz); a DME reply is a pulse pair, and the airborne unit computes range from round-trip time.

TACAN (UHF 960–1215 MHz) provides bearing and DME; military aircraft use it directly, civil aircraft normally use only the DME portion of a VORTAC.

VOR accuracy ≈ ±1–2° at the receiver in good conditions; check ident, monitor the flag, and cross-check with a second navaid or GNSS where available.

NDB frequencies 190–535 kHz (LF/MF), AM modulated with a Morse ident; ADF receiver is tuned to the station frequency and displays relative bearing.

ADF needle points to the relative bearing of the station (angle from aircraft heading), not the magnetic bearing; magnetic bearing = heading + relative bearing.

QDM = magnetic bearing to the station; QDR = magnetic bearing from the station; they differ by 180°. Use QDM for homing.

Relative bearing 0° = station ahead, 90° = right, 180° = behind, 270° = left. The fixed-card ADF dial shows relative bearing; a rotating card shows magnetic bearing.

NDB is subject to night effect (skywave ionospheric refraction), causing bearing errors at night and near dawn/dusk, especially at long range.

Coastal refraction, mountain effect and thunderstorm (sferic) interference cause bearing errors; the needle may swing or point to a false null.

ADF is susceptible to quadrantal error from the aircraft fuselage and to line-of-sight blockage; recheck the ident and use a second navaid to confirm position.

Homing to an NDB in a crosswind produces a curved track; to track a fixed QDM, apply a wind correction angle (tracking, not homing).

NDB range depends on power and propagation; typically 25–200 NM. ADF is not a precision aid; use it as a backup or for non-precision approaches.

ILS localiser band 108.10–111.95 MHz (odd tenths), glidepath 329.15–335.00 MHz; ident is a three-letter Morse code.

Localiser provides lateral guidance (course) with 90 Hz/150 Hz modulation; glidepath provides vertical guidance. Full-scale CDI deflection is ±2.5° for localiser.

Glidepath angle is normally 3° (range 2.5–3.5°); fly the published descent rate, e.g. about 300 ft/NM at 3°.

Marker beacons: outer marker (blue, 400 Hz, ~4 NM from threshold), middle marker (amber, 1300 Hz, ~3500 ft from threshold), inner marker (white, 3000 Hz).

Decision altitude/height (DA/DH) applies to ILS; at DA/DH either land or go around. Below DA/DH, only visual reference permits continuation.

Localiser sensitive area: aircraft and vehicles must not enter; ILS signals are distorted by reflections from large objects, causing scalloping or false courses.

ILS categories: CAT I (DA 200 ft, RVR 550 m), CAT II (DA 100 ft, RVR 300 m), CAT III (below 100 ft, RVR down to 0).

Glidepath is vertically polarised and more susceptible to terrain reflection; localiser is horizontally polarised. Both require clear approach paths.

Missed approach: at DA/DH with no visual reference, execute the published missed approach procedure immediately.

Primary radar (PSR) transmits pulses and detects echoes from targets; range = (c × time delay) / 2. Uses include airport surface surveillance and weather detection.

Secondary radar (SSR) interrogates transponders; replies carry Mode A (identity squawk) and Mode C (altitude). Range accuracy depends on timing, bearing on antenna.

ATC surveillance uses 1030 MHz interrogation and 1090 MHz reply; Mode S provides selective addressing and data link.

Airborne weather radar operates in X-band (~9.3 GHz) or C-band (~5.5 GHz); shorter wavelength gives better resolution but more attenuation in heavy rain.

Weather radar detects precipitation, not clear air turbulence; reflectivity depends on droplet size and density. Attenuation can hide distant storms behind near ones.

Tilt management: adjust tilt so the beam paints the storm at the correct range; over-tilt hides weather, under-tilt shows ground clutter.

Radar shadow: a strong storm attenuates the beam, producing a shadow beyond it that may conceal another cell.

Radar display is stabilised (heading or track) or unstabilised; know which mode is selected to interpret the picture correctly.

Radar altimeter (separate from weather radar) measures height above terrain using a downward beam; used for approach minimums and terrain awareness.

RNAV permits flight on any desired path within the coverage of navigation aids or GNSS, rather than direct-to-station tracking.

Waypoints: fly-by (turn anticipation, aircraft turns before the waypoint) and fly-over (aircraft overflies the waypoint before turning).

RNAV equipment types: basic RNAV (B-RNAV, ±5 NM) and precision RNAV (P-RNAV, ±1 NM); check the aircraft's approved capability.

Required navigation performance (RNP) adds on-board performance monitoring and alerting, with a specified accuracy value (e.g. RNP 1, RNP 0.3).

Track-to-track and turn anticipation depend on the flight management system; monitor the active leg and the distance to the next waypoint.

RNAV route structure uses waypoints defined by coordinates or by radial/distance from navaids; verify the database is current and the correct procedure is loaded.

When a navigation aid fails, RNAV equipment may revert to dead reckoning; monitor position and cross-check with raw data or GNSS.

RNAV approach minima depend on the equipment and the procedure; do not use RNAV minima unless the aircraft and crew are approved for them.

GNSS includes GPS (USA), GLONASS (Russia), Galileo (EU) and BeiDou (China); each constellation provides ranging signals from satellites.

GPS nominal constellation: 24 satellites in 6 orbital planes, altitude ~20,200 km, 12-hour period; at least 4 satellites needed for a 3-D fix.

Position is computed by trilateration from satellite ranges; a fourth satellite resolves receiver clock bias.

Dilution of precision (DOP) describes geometric quality; high DOP means poor geometry and degraded accuracy even with good signals.

PBN specifies navigation performance in terms of RNAV and RNP; RNP requires on-board performance monitoring and alerting.

GNSS accuracy is affected by ionospheric and tropospheric delay, multipath, satellite clock and ephemeris errors, and receiver noise.

RAIM (receiver autonomous integrity monitoring) detects a faulty satellite; with 5 satellites RAIM can detect, with 6 it can exclude.

PBN approach minima (LNAV, LNAV/VNAV, LP, LPV) depend on the augmentation and the aircraft's approved capability; do not descend below minima without the required visual reference.

GBAS (ground-based augmentation system) uses a ground station to compute corrections and integrity data, broadcast to aircraft over VHF; supports precision approach (GLS).

SBAS (satellite-based augmentation system) uses geostationary satellites to broadcast corrections and integrity data; examples include WAAS (USA), EGNOS (Europe), MSAS (Japan), GAGAN (India).

SBAS enables LPV approaches with vertical guidance; LPV minima can be as low as 200 ft, comparable to CAT I ILS.

GBAS can support CAT I and higher minima depending on the installation; it is limited to the coverage of the ground station.

Augmentation improves accuracy, integrity, continuity and availability of GNSS; without augmentation, standalone GNSS may not meet approach integrity requirements.

Integrity monitoring: SBAS broadcasts integrity information; GBAS monitors satellite signals locally and alerts users to faults.

SBAS/GBAS signals are line-of-sight; terrain and buildings can block reception, and ionospheric storms can degrade SBAS performance.

Check that the aircraft is approved and the receiver is capable of the specific SBAS/GBAS service before using associated minima.

CDI: centre = on course; full-scale deflection = 10° for VOR, 2.5° for localiser. Fly toward the needle to intercept.

HSI combines heading, CDI and bearing pointer; the course selector sets the desired track and the TO/FROM flag indicates direction.

RMI shows magnetic bearing to the station directly with a rotating card; relative bearing = magnetic bearing − heading.

OBS: rotate to select the desired radial; the CDI then shows deviation from that radial. The ambiguity resolves with the TO/FROM flag.

VOR cross-check: identify two radials from different stations, or one radial plus DME, to fix position.

ILS: localiser and glidepath needles form a cross; fly toward the needle. Do not chase large deflections; correct smoothly.

DME distance is slant range; when directly overhead, indicated distance equals aircraft altitude, not zero.

Always confirm the station ident (Morse code) and monitor navigation flags; a flagged instrument is unreliable.

VOR errors: scalloping, course bending near terrain, cone of confusion overhead, and multipath reflections from buildings.

NDB/ADF errors: night effect (skywave), coastal refraction, mountain effect, thunderstorm static, and quadrantal error from the airframe.

ILS errors: reflections from aircraft and vehicles in the sensitive area cause scalloping and false courses; glidepath is affected by terrain and snow.

DME errors: slant-range error is largest overhead; system accuracy is typically ±0.5 NM or 3% of range, whichever is greater.

GNSS errors: ionospheric delay (largest near the equator and at high latitudes), multipath, jamming and spoofing; RAIM detects but does not correct.

Interference: co-channel and adjacent-channel, cross-modulation, precipitation static, and deliberate jamming. Loss of signal triggers warning flags.

Terrain and buildings block VHF/UHF line-of-sight; expect reduced range at low altitude and in mountainous areas.

Cross-check all navaids against each other and against GNSS; a single anomalous indication should be treated as suspect until confirmed.

Before relying on a VOR, confirm the Morse ident and that the NAV flag is out of view.

Use the published radial and DME distance to fix position; compare with the charted position.

When station passage occurs, the TO/FROM flag changes and the CDI becomes erratic (cone of confusion).

For a DME arc, maintain a constant DME distance while turning to keep the bearing pointer at 90° to the station.

Confirm the correct localiser ident and that the approach is the one published for the runway in use.

At the outer marker, check altitude against the published procedure and set the missed approach altitude.

Do not descend below DA/DH unless the required visual reference is in sight.

If the localiser or glidepath flag appears, execute the missed approach.

Check the number of satellites tracked and the DOP before relying on GNSS for an approach.

Confirm RAIM is available and the receiver is approved for the intended procedure.

Cross-check GNSS position with VOR/DME or NDB where possible.

Be alert for jamming or spoofing; an unexpected position jump should be treated as suspect.