Aircraft Navigation Terms and Definitions

Aircraft Navigation Terms and DefinitionsAircraft Navigation Terms and DefinitionsAircraft navigation terms can often be confusing, especially when a pilot doesnt use them every day. Experience with cross-country flights and practical use of navigation techniques make these terms easier to identify. In the meantime, heres a review of navigation terms and the corresponding definitions. Speeds Calibrated Airspeed (CAS) - Indicated airspeed corrected for instrument or position inaccuracies. The calibrated airspeed can be found in the pilot operating handbook or on the airspeed indicator.Indicated Airspeed (IAS) - The airspeed read directly from the airspeed indicator.Groundspeed (GS) - The actual speed of the airplane passing over the ground. Groundspeed is true airspeed corrected for wind. You can find the aircraft ground speed by calculating it with a flight computer.True Airspeed (TAS) - The actual speed relative to the surrounding air. True airspeed is calibrated airspeed correc ted for nonstandard pressure and temperature. You can determine the aircrafts true airspeed with a flight computer. Altitudes Indicated Altitude - The altitude depicted on the altimeter. Remember that indicated altitude is the vertical distance above mean sea level (MSL), bedrngnis above the ground.Density Altitude - Pressure altitude corrected for nonstandard temperature. You can calculate density altitude with a flight computer.Pressure Altitude - The altitude shown on the altimeter when the altimeter is set to 29.92 inches or standard atmospheric pressure.Absolute Altitude - The vertical distance of the aircraft above the surface of the earth, or above ground level (AGL). True Altitude - The aircraft altitude above mean sea level (MSL). You can determine the true altitude with a flight computer. Directional True North - The geographic north pole is located at the northernmost point. True north is not the same location as magnetic north, due to the rotation of the earth i n relation to the earths magnetic field.Magnetic North - The northern location where the Earths magnetic force has the most downward pull. If you were to stand on magnetic north, a magnetic compass would point straight down. Magnetic north varies due to shifts in the Earths core and is at a different location than true north.Magnetic Variation - The angular difference between true north and magnetic north. Also known as declination. Magnetic Deviation - A magnetic anomaly that affects the compass. The magnetic compass in the aircraft is affected by surrounding magnetic and electrical disturbances in the airplane.Compass Heading - The aircrafts magnetic heading corrected for deviation. The deviation is found on a compass card or a placard near the compass, and it usually varies by just a degree or two.Magnetic Course - True course corrected for magnetic variation.Magnetic Heading - True heading corrected for magnetic variation. You can determine the magnetic variation from a sectiona l map. True Course - The aircrafts course over the ground relative to true north. True course is measured with a navigation plotter and a sectional map.True Heading - True course corrected for wind. Basic Calculations Time distance/groundspeed (td/GS)Distance groundspeed/time (dGS/t)Groundspeed distance/time (GSd/t)Fuel consumption Gallons/hour x time (GPH x T) Standard Atmospheric Conditions Standard Temperature 15 degrees Celsius or 59 degrees Fahrenheit.Standard Pressure 29.92 mercury or 14.5 psi or 1013.2 mb.