Brunei DCA CPL(A) General Navigation flashcards

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

Oblate spheroid

The Earth's shape, flattened at the poles and bulging at the equator; equatorial radius is about 6378 km and polar radius about 6357 km.

Nautical mile

One minute of arc of latitude on the Earth's surface, approximately 1852 metres; used as the standard unit of distance in air navigation.

Great-circle distance formula

cos(d) = sin(Lat1)sin(Lat2) + cos(Lat1)cos(Lat2)cos(dLon), giving the shortest surface distance between two points in angular measure.

Departure formula

Departure in nautical miles equals change of longitude in minutes multiplied by the cosine of the mean latitude of the leg.

WGS-84 datum

The geodetic reference system used for most modern charts and GNSS positions; positions must be converted if the chart uses another datum.

Decimal degrees conversion

Decimal degrees = degrees + minutes/60 + seconds/3600; used to convert charted positions into a form suitable for calculation.

Rhumb line

A line crossing every meridian at the same true track; it plots as a straight line on a Mercator chart but is not the shortest path.

Great-circle track

The shortest path between two points; its true track changes continuously along the route and plots curved on a Mercator chart.

Vertex

The highest latitude point on a great-circle route, where the track direction changes by 180 degrees between the two halves.

Mercator projection

A conformal cylindrical projection on which rhumb lines are straight; scale increases with latitude, so it is unsuitable for polar navigation.

Lambert conformal conic

A conformal projection using a cone; great circles plot nearly straight and it is widely used for mid-latitude area and en-route charts.

Chart scale

The ratio of chart distance to Earth distance; large-scale charts show more detail, small-scale charts cover larger areas with less detail.

Drift angle

The angular difference between true heading and true track, caused by wind; positive drift indicates the aircraft is being pushed right.

Wind correction angle

The angle applied to the desired track to counter drift; sin(WCA) = (wind speed/TAS) × sin(wind direction − track).

Groundspeed

The speed of the aircraft over the ground, found by combining true airspeed with the wind vector in the wind triangle.

Track made good

The actual path over the ground derived from two position fixes; comparing it with planned track gives the actual drift.

Variation

The angle between true north and magnetic north at a location; east variation is added when converting true to magnetic.

Deviation

The angle between magnetic north and compass north caused by aircraft magnetic fields; it is specific to the aircraft and heading.

Compass conversion rule

True + Variation = Magnetic; Magnetic + Deviation = Compass. East values are added and west values subtracted in this direction.

Magnetic dip

The vertical component of the Earth's magnetic field; it is zero at the magnetic equator and 90 degrees at the magnetic poles.

Local mean time

LMT = UTC + longitude/15 degrees, with east longitude positive and west longitude negative; it varies continuously with longitude.

Equation of time

The difference between apparent solar time and mean solar time, varying by up to about 16 minutes over the year.

International Date Line

A line near 180 degrees longitude where the calendar date changes by one day when crossing east or west.

Specific range

Distance flown per unit of fuel used; it peaks near optimum cruise altitude and speed and decreases in a headwind.

Endurance

The total time an aircraft can remain airborne, calculated as usable fuel divided by fuel flow rate.

Equal-time point

The point on a route where the time to return to base equals the time to continue to destination, allowing for wind.

VOR radial

A magnetic bearing from a VOR station; the CDI shows the selected radial and TO/FROM sense for position fixing.

ADF relative bearing

The angle measured clockwise from the aircraft nose to the NDB; magnetic bearing equals relative bearing plus magnetic heading.

Position fix geometry

The best fix comes from lines of position crossing near 90 degrees; shallow crossing angles greatly magnify position error.

RAIM

Receiver autonomous integrity monitoring, which detects and isolates faulty GNSS satellite signals using redundant range measurements.

RNP specification

Required navigation performance states the total system error in nautical miles, achieved 95 percent of the time, with on-board monitoring and alerting.

Centre of gravity

CG = total moment / total mass; it must remain within certified forward and aft limits for stability and control throughout the flight.

Zero-fuel mass

The aircraft mass without usable fuel; it is a structural limit that must not be exceeded when loading payload and crew.