DGCA CPL Air Navigation flashcards

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

Oblate Spheroid

Earth model flattened at the poles, with equatorial radius about 6,378 km and polar radius about 6,357 km; the flattening ratio is about 1/297.

Great Circle

Circle on Earth's surface whose plane passes through Earth's centre; it gives the shortest surface distance between two points and bisects all other great circles.

Rhumb Line

Line crossing every meridian at the same angle; it plots straight on a Mercator chart but is longer than a great circle except along the equator or a meridian.

Magnetic Variation

Angle between true north and magnetic north at a location; easterly variation means magnetic bearing is less than true bearing, summarised as variation east, magnetic least.

Magnetic Dip

Inclination of Earth's magnetic field to the horizontal; it is zero at the magnetic equator and 90 degrees at the magnetic poles, causing compass errors in high latitudes.

Compass Deviation

Error caused by the aircraft's own magnetic fields and electrical currents, varying with heading; it is recorded on a deviation card, and magnetic heading equals compass heading plus easterly deviation.

Local Mean Time

Time based on the Sun's mean position at a location; it changes by four minutes per degree of longitude, with LMT equal to UTC plus east longitude divided by 15.

International Date Line

Generally the 180-degree meridian where the date changes; crossing westward adds one day and crossing eastward subtracts one day, subject to political adjustments.

Mercator Projection

Conformal cylindrical projection on which rhumb lines plot as straight lines; scale increases with latitude, and great circles appear as curves rather than straight lines.

Lambert Conformal Conic

Conic projection with two standard parallels, often used for aeronautical charts; it is conformal, and straight lines approximate great circles over the chart's usable area.

One in Sixty Rule

Approximation stating that a one-degree angular error produces one nautical mile of offset after 60 nautical miles; used for track error and closing angle calculations.

Wind Triangle

Vector relationship among true airspeed, wind velocity, and ground speed; it yields drift angle and wind correction angle needed to maintain a desired track.

QNH

Altimeter setting that makes the altimeter indicate elevation above mean sea level when on the ground; used for terrain clearance and approach altimetry.

QFE

Altimeter setting that makes the altimeter read zero at a specified reference point, usually aerodrome elevation; used for height above aerodrome.

QNE

Standard altimeter setting of 1013.25 hPa; used above transition altitude so that all aircraft fly common flight levels referenced to standard pressure.

Specific Range

Distance flown per unit of fuel consumed, usually nautical miles per kilogram; it varies with speed, altitude, temperature, and wind and is used to compare cruise efficiency.

ADF Relative Bearing

Bearing of a station measured clockwise from aircraft heading; magnetic bearing to the station equals relative bearing plus magnetic heading, with 360 degrees subtracted if needed.

VOR Radial

Magnetic bearing from a VOR station outward; an aircraft on the 090 radial is east of the station, and the CDI indicates deviation from the selected radial.

DME Slant Range

Line-of-sight distance from aircraft to DME transponder, not ground distance; the difference from ground range increases with altitude but is small at normal ranges.

ILS Localizer

VHF guidance component providing lateral course guidance to the runway; it operates in the 108–112 MHz band with 90 Hz left and 150 Hz right modulation.

ILS Glideslope

UHF guidance component providing vertical path guidance, typically at 3 degrees; it operates in the 329–335 MHz band paired with the localizer frequency.

Marker Beacon

Fan-shaped radio beacon at a fixed distance from the runway threshold; outer, middle, and inner markers provide aural and visual indications of approach progress.

Secondary Surveillance Radar

Radar system that interrogates aircraft transponders; replies provide identification, altitude, and other data, unlike primary radar skin returns.

NDB Frequency Band

Aircraft NDBs operate in the 190–1750 kHz range, usually in the low-frequency band; ADF receivers use these signals to derive bearing information.

GNSS Pseudorange

Apparent range from receiver to satellite derived from signal travel time, including receiver and satellite clock errors; four satellites are needed for a three-dimensional fix.

RAIM

Receiver Autonomous Integrity Monitoring; uses redundant satellite measurements to detect and possibly exclude faulty signals, requiring at least five satellites for detection.

Geometric Dilution of Precision

Factor describing how satellite geometry amplifies ranging errors; lower GDOP values indicate better geometry and a more accurate position solution.

SBAS

Satellite-Based Augmentation System, such as WAAS or EGNOS; it broadcasts corrections and integrity data to improve GNSS accuracy and availability for aviation.

GBAS

Ground-Based Augmentation System; it provides local differential corrections and integrity monitoring, supporting precision approach guidance near an airport.

RNP

Required Navigation Performance; it specifies on-board performance monitoring and alerting, allowing aircraft to fly precise paths within a defined containment volume.

ADS-B Out

Automatic Dependent Surveillance-Broadcast transmission from aircraft containing position, velocity, and identity; it enables surveillance without primary radar interrogation.

Inertial Navigation System

Self-contained system using accelerometers and gyroscopes to compute position and velocity; it drifts over time and requires initial alignment before flight.