Brunei DCA CPL(A) Radio Navigation flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Wavelength formula

Wavelength in metres equals 300 divided by frequency in megahertz. This relationship explains why VHF and UHF navaids are line-of-sight and why higher frequencies need shorter antennas.

Radio horizon formula

The radio horizon in nautical miles is approximately 1.23 times the square root of the height in feet. Add transmitter and receiver horizons to find total usable range.

VOR frequency band

VOR operates from 108.0 to 117.95 megahertz with 50 kilohertz spacing. Frequencies from 108.0 to 111.85 ending in odd tenths are shared with ILS localisers, so confirm the ident.

VOR radial definition

A VOR radial is the magnetic bearing from the station to the aircraft. The course selector sets the desired radial, and the TO/FROM flag indicates whether the aircraft is flying toward or away from the station.

CDI full-scale deflection

For VOR the course deviation indicator reaches full scale at about ten degrees from the selected radial, roughly two degrees per dot. For a localiser, full scale is about 2.5 degrees.

Cone of confusion

Directly overhead a VOR, within about 40 degrees of the station, the course deviation indicator becomes erratic and unreliable. Use other navigation guidance during station passage.

DME slant range

DME measures slant range, not ground distance. The error is largest directly overhead, where the indicated distance equals the aircraft altitude rather than zero.

TACAN frequency band

TACAN operates in the UHF band from 960 to 1215 megahertz and provides both bearing and distance. Civil aircraft using a VORTAC normally use only the DME portion.

ADF relative bearing

The ADF needle points to the relative bearing of the station measured from the aircraft heading. Magnetic bearing equals heading plus relative bearing, with 360 degrees subtracted if the result exceeds 360.

QDM and QDR

QDM is the magnetic bearing to the station, used for homing. QDR is the magnetic bearing from the station. The two values differ by 180 degrees.

Night effect on NDB

At night, skywave propagation through the ionosphere can cause bearing errors on NDB/ADF, especially at long range and near dawn or dusk. Cross-check with another navaid.

ILS localiser band

ILS localisers operate from 108.10 to 111.95 megahertz on odd tenths. The ident is a three-letter Morse code, and the localiser provides lateral guidance with 90 and 150 hertz modulation.

Glidepath angle

The ILS glidepath is normally three degrees, ranging from 2.5 to 3.5 degrees. At three degrees the descent rate is about 300 feet per nautical mile.

Marker beacon colours

The outer marker is blue and modulated at 400 hertz, about four nautical miles from the threshold. The middle marker is amber at 1300 hertz, and the inner marker is white at 3000 hertz.

ILS categories

Category I has a decision altitude of 200 feet and RVR of 550 metres. Category II has 100 feet and 300 metres. Category III permits lower minima down to zero RVR.

Primary radar principle

Primary radar transmits pulses and detects echoes from targets. Range equals the speed of light multiplied by the round-trip time delay, divided by two.

Secondary surveillance radar

SSR interrogates transponders at 1030 megahertz and receives replies at 1090 megahertz. Mode A gives identity and Mode C gives altitude. Mode S adds selective addressing.

Weather radar band

Airborne weather radar uses X-band near 9.3 gigahertz or C-band near 5.5 gigahertz. Shorter wavelength gives better resolution but greater attenuation in heavy rain.

Radar attenuation shadow

A strong storm attenuates the radar beam, producing a shadow beyond it that may conceal another cell. Adjust tilt and range to avoid missing weather behind a near storm.

Fly-by waypoint

A fly-by waypoint allows the aircraft to begin turning before reaching the waypoint, using turn anticipation. A fly-over waypoint requires the aircraft to overfly the point before turning.

RNAV accuracy values

Basic RNAV requires plus or minus five nautical miles, while precision RNAV requires plus or minus one nautical mile. Confirm the aircraft's approved capability before using associated routes.

Required navigation performance

RNP specifies a navigation accuracy value and requires on-board performance monitoring and alerting. If performance falls below the value, the crew is alerted.

GNSS constellations

GNSS includes GPS, GLONASS, Galileo and BeiDou. Each constellation provides ranging signals from satellites, and a receiver may combine several constellations to improve availability and accuracy.

GNSS position fix

A GNSS receiver computes position by trilateration from satellite ranges. At least four satellites are needed for a three-dimensional fix and to resolve the receiver clock bias.

Dilution of precision

DOP describes the geometric quality of the satellite constellation. High DOP means poor geometry and degraded accuracy even when signals are strong and clean.

RAIM function

Receiver autonomous integrity monitoring detects a faulty satellite. With five satellites RAIM can detect a fault, and with six it can exclude the faulty satellite from the solution.

SBAS examples

Satellite-based augmentation systems include WAAS in the United States, EGNOS in Europe, MSAS in Japan and GAGAN in India. They broadcast corrections and integrity data from geostationary satellites.

GBAS principle

A ground-based augmentation system computes corrections and integrity data at a ground station and broadcasts them to aircraft over VHF. It supports precision approach within the station's coverage.

LPV approach

A localiser performance with vertical guidance approach uses SBAS to provide lateral and vertical guidance. Minima can be as low as 200 feet, comparable to Category I ILS.

HSI display

The horizontal situation indicator combines heading, course deviation and a bearing pointer. The course selector sets the desired track, and the TO/FROM flag shows the direction.

DME overhead indication

Directly overhead a DME station, the indicated distance equals the aircraft altitude rather than zero. This is the slant-range error and is largest at high altitude over the station.

GNSS ionospheric error

Ionospheric delay is the largest GNSS error source and varies with solar activity, being greatest near the equator and at high latitudes. SBAS and dual-frequency receivers reduce it.