CPL Navigation (Sri Lanka CAA Pilot Licence Examinations) flashcards

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

Great circle

The shortest path between two points on the Earth's surface, formed by the intersection of the surface with a plane through the Earth's centre. Track angle changes continuously along it.

Rhumb line

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

Departure

The distance in nautical miles between two meridians along a parallel of latitude, equal to 60 times the change in longitude times the cosine of the latitude.

Conversion angle

The angular difference between a great circle track and the rhumb line joining the same two points, approximately half the change in longitude times the sine of the mean latitude.

Mercator projection

A conformal cylindrical projection on which meridians are parallel straight lines and the scale expands with latitude as the secant of latitude, so rhumb lines plot straight.

Lambert conformal conic

A conformal conic projection widely used for aeronautical charts, on which great circles plot as approximately straight lines and scale is constant along each parallel.

Variation

The angular difference between true north and magnetic north at a given place, shown on charts as isogonals; east variation is subtracted from true to obtain magnetic.

Deviation

The angular difference between magnetic north and the aircraft's compass north caused by aircraft magnetic fields, read from the compass swing card and applied to magnetic heading.

Drift angle

The angle between the aircraft's heading and the track actually made good, caused by the crosswind component; positive when the wind pushes the aircraft right of heading.

Wind triangle

The vector relationship between true airspeed and heading, wind velocity, and resulting ground speed and track, solved graphically or with a flight computer.

Point of no return

The point along a route from which it takes the same time to return to the departure point as to continue to the destination, given the prevailing winds and endurance.

Critical point

The point along a route where the fuel required to return to base equals the fuel required to continue to destination, calculated from safe endurance and fuel flows.

1 in 60 rule

A track error of one nautical mile over a distance of 60 nautical miles corresponds to an angular error of one degree; used to compute track error and closing angle.

Closing angle

The angle subtended at the aircraft by the remaining distance to destination and the distance off track, used with track error to compute the heading correction.

VOR radial

The magnetic bearing from a VOR station to the aircraft, displayed as the selected course when the CDI is centred with a FROM indication.

QDM

The magnetic bearing from the aircraft to a radio navigation station; it equals the aircraft's magnetic heading plus the relative bearing shown on the ADF.

QDR

The magnetic bearing from a radio navigation station to the aircraft; it is the reciprocal of the QDM and corresponds to the VOR radial.

RAIM

Receiver Autonomous Integrity Monitoring, a GNSS function that detects a faulty satellite by comparing redundant range measurements; requires at least five satellites for detection.

DME slant range

The line-of-sight distance from the aircraft to the DME transponder; ground distance is found from the slant range and aircraft altitude using Pythagoras.

ILS localiser

The lateral guidance component of an ILS, transmitting on VHF and providing course guidance along the extended runway centreline within a protected service volume.

QNH

The altimeter subscale setting that, when set on the ground at the aerodrome, causes the altimeter to indicate the aerodrome elevation above mean sea level.

QFE

The altimeter subscale setting that causes the altimeter to read zero on the aerodrome reference point, giving height above the aerodrome rather than altitude.

QNE

The standard pressure setting of 1013.25 hPa used above the transition level, giving flight levels rather than altitude above mean sea level.

Transition altitude

The altitude at or below which the altimeter is set to local QNH; above the transition level, standard pressure 1013.25 hPa is used.

Density altitude

The pressure altitude corrected for non-standard temperature, approximately pressure altitude plus 120 feet for each degree Celsius above ISA temperature.

True altitude

The actual height above mean sea level; it differs from indicated altitude when temperature and pressure differ from ISA, with cold air making the aircraft lower than indicated.

ISA

The International Standard Atmosphere, with sea-level temperature 15 degrees Celsius, pressure 1013.25 hPa, and a lapse rate of 1.98 degrees Celsius per 1,000 feet.

Dead reckoning

A navigation technique computing position from a known starting point using heading, true airspeed, wind, and elapsed time, without reference to external features.

Pilotage

Navigation by visual reference to ground features such as towns, rivers, and roads, compared with the chart to establish position and maintain track.

Heading correction

The sum of track error and closing angle, applied to the current heading to regain and then maintain the intended track to destination.

Top of descent

The point where descent should begin, computed by dividing the altitude to lose by the required gradient; on a three-degree path about 318 feet per nautical mile.

Ground speed

The aircraft's speed over the ground, equal to true airspeed adjusted for the along-track wind component; headwind reduces it and tailwind increases it.