Aviation Radio Navigation and Radar Systems

Comprehensive practice flashcards featuring key aviation navigation vocabulary, operational principles, system frequencies, and accuracy requirements derived from lecture exam material.

Beat Frequency Oscillator (BFO)

A selector on an ADF receiver used to hear the IDENT tone of NDB stations radiating a continuous wave signal.

Non-Directional Beacon (NDB) Radiation Pattern

The signal pattern transmitted in the horizontal plane by an NDB facility, which is omnidirectional.

ADF Bearing Greatest Inaccuracy

The navigational disturbance most likely to cause the largest bearing error in an ADF system, identified as local thunderstorm activity.

VOR Operating Principle

A VHF radio navigation aid whose bearing measurement is determined by the phase comparison between a reference signal and a variable directional signal.

VOR Operating Frequency Band

The VHF band covering radio frequencies from $108\text{ MHz}$ to $117.95\text{ MHz}$.

VOR Variable Signal

The directional signal of a conventional VOR that rotates at a rate of $30\text{ times per second}$, providing the characteristics of a $30\text{ Hz}$ amplitude modulation.

VOR Radial Track Type

The line an aircraft tracks when flying along a VOR radial, which follows a great circle track.

Distance Measuring Equipment (DME)

A secondary radar system operating in the UHF band on frequencies between $962\text{ MHz}$ and $1213\text{ MHz}$ that calculates slant range from interrogation pulse transit times.

DME Beacon Saturation

The operating limit of a conventional DME ground station occurring when the number of simultaneous interrogations exceeds $100$.

DME Range Search Indication

The continuous rotation of airborne DME display counters throughout their range when seeking to achieve lock-on.

DME Memory Mode

The temporary fallback state to which an airborne DME switches in the first instance upon experiencing a reduction in signal strength while in tracking mode.

Tactical Air Navigation (TACAN)

A military navigation station capable of providing civilian aircraft with DME distance.

Instrument Landing System (ILS) Localiser

A VHF runway approach transmitter radiating two overlapping lobes modulated at $90\text{ Hz}$ and $150\text{ Hz}$ on the same carrier frequency, providing horizontal course guidance.

ILS Glide Path (Glide Slope)

An ILS guidance transmitter operating in the UHF band to provide vertical guidance along a descent profile (typically $3^\circ$).

Outer Marker (OM)

An ILS marker beacon transmitting on $75\text{ MHz}$ modulated at $400\text{ Hz}$ (two dashes per second) that triggers a flashing blue cockpit indicator.

Middle Marker (MM)

An ILS marker beacon transmitting on $75\text{ MHz}$ modulated at $1300\text{ Hz}$ (alternate dots and dashes) that triggers a flashing amber cockpit indicator.

Marker Beacon Sequence

The color illumination sequence experienced in the cockpit when crossing markers on approach: blue (Outer), amber (Middle), and white (Inner).

Microwave Landing System (MLS) Azimuth Coverage

Approach guidance operating in the SHF band that provides fan-shaped horizontal coverage of $\pm 40^\circ$ about the nominal courseline out to $20\text{ NM}$.

Pulse Length (Radar)

The transmission duration of an individual radar pulse, which determines the minimum measurable target range and target range discrimination.

Pulse Recurrence Frequency (PRF)

The number of radar pulses transmitted per second, which directly dictates the maximum unambiguous detection range.

Primary Radar Power-to-Range Law

The physical rule specifying that to double the effective detection range of a primary radar, transmitter power must be increased by a factor of $16$.

Aerodrome Surface Movement Radar (ASMR)

A high-resolution ground radar operating in the SHF band with an antenna rotating at approximately $60\text{ rpm}$, sometimes capable of revealing aircraft type and shape.

ISO-ECHO (Airborne Weather Radar)

A radar display function used to detect areas of possible severe turbulence in cloud formations by highlighting steep rainfall rate contours.

AWR Mapping Mode Beam

A radar transmission utilising a cosecant-squared radiation pattern effective up to $50\text{ NM}$ to $60\text{ NM}$ to produce ground returns independent of range.

Secondary Surveillance Radar (SSR) Interrogation Frequencies

The paired frequencies where the ground SSR station transmits interrogations on $1030\text{ MHz}$ and receives aircraft replies on $1090\text{ MHz}$.

SSR Mode C

A transponder operating mode that automatically transmits the aircraft pressure altitude referenced to the standard pressure datum of $1013.25\text{ hPa}$.

SSR Code 7500

The international transponder emergency squawk code selected to report unlawful interference with the aircraft flight operation.

SSR Code 7600

The dedicated transponder squawk code selected to announce two-way radio communication failure.

SSR Code 7700

The dedicated transponder squawk code selected to announce a state of general aircraft emergency.

SSR Code 2000

The transponder code selected when entering controlled airspace from an area where transponder operation was not previously required.

Area Navigation (RNAV)

A navigation method defined in ICAO Annex 11 permitting aircraft operation on any desired flight path within the coverage of station-referenced navigation aids, within self-contained aid limits, or a combination thereof.

Basic RNAV (B-RNAV) Accuracy

An area navigation standard requiring a track-keeping accuracy of $\pm 5\text{ NM}$ or better for $95\%$ of the flight time.

Precision RNAV (P-RNAV) Accuracy

An area navigation performance standard requiring a track-keeping accuracy of $1.0\text{ NM}$ standard deviation or better.

Doppler Navigation System

A self-contained navigation aid based on radar principles that senses an apparent transmitted frequency shift proportional to velocity to compute ground speed and drift.

Loran-C

A hyperbolic radio navigation system operating on carrier frequencies between $90\text{ kHz}$ and $110\text{ kHz}$ using differential range measurement via pulse arrival techniques.

Pseudo-Range (GNSS/GPS)

The measured distance from a satellite to a receiver calculated by multiplying signal propagation time by the speed of light, which still contains receiver clock error.

WGS-84

The mathematical reference ellipsoid model used by NAVSTAR/GPS to calculate three-dimensional position (latitude, longitude, and height).

NAVSTAR/GPS Space Segment Constellation

The baseline constellation of $24\text{ operational satellites}$ arranged across $6\text{ orbital planes}$ with $4\text{ satellites}$ in each plane, inclined at $55^\circ$ to the equatorial plane.

Receiver Autonomous Integrity Monitoring (RAIM)

An internal receiver software function requiring $5\text{ satellites}$ to detect a faulty satellite measurement and $6\text{ satellites}$ to isolate and exclude the fault.

Selective Availability (SA)

The intentional degradation of civil GPS navigation accuracy formerly implemented by dithering the satellite clock and corrupting ephemeris data.

Differential GPS (D-GPS)

A navigation augmentation method in which fixed ground stations calculate position and range errors and broadcast real-time correction data to nearby airborne receivers.

GPS Search the Sky

An automatic initialization routine executed upon receiver activation when no stored almanac or satellite ephemeris data is present in memory.