Aviation Math Glossary for Pilots
This glossary explains the terms that appear across PilotDesk calculators and flight-planning tools. It is written for quick lookup: what the term means, which units are normally used, and which calculation it connects to.
Airspeed terms
IAS — indicated airspeed: the value shown on the airspeed indicator before correcting for instrument and position error. CAS — calibrated airspeed: IAS corrected for those errors. TAS — true airspeed: the airplane's speed through the air mass after accounting for air density. Groundspeed: speed across the ground after wind is included. Groundspeed drives time, descent-rate, and climb-gradient calculations. See the TAS estimate and time/speed/distance calculator.
Wind and navigation terms
Wind correction angle (WCA): the heading correction used to counter crosswind and maintain a desired course. Headwind component: the portion of wind opposing travel along the runway or course. Tailwind component: the portion pushing in the direction of travel. Crosswind component: the portion acting perpendicular to the runway or course. True direction is referenced to true north, while magnetic direction is referenced to magnetic north. See the wind triangle, crosswind, and true/magnetic tools.
Altitude and atmosphere terms
Pressure altitude: altitude referenced to the standard pressure datum of 29.92 inHg. Density altitude: the standard-atmosphere altitude corresponding to the current air density. ISA: International Standard Atmosphere, the reference model used for standard pressure and temperature relationships. OAT: outside air temperature. Dew point: the temperature at which air becomes saturated if cooled at constant pressure. See the pressure altitude, density altitude, ISA temperature, and estimated cloud base tools.
Climb and descent terms
FPM: feet per minute, a vertical-speed unit. ft/NM: feet gained or lost for each nautical mile traveled over the ground. Climb gradient: vertical gain per horizontal distance. Flight-path angle: the geometric angle between the flight path and the horizontal. Top of descent (TOD): a planning point where descent begins to meet a target altitude, gradient, or path. See climb gradient, gradient/angle, 3° descent, and TOD.
Turn and maneuver terms
Load factor: lift divided by aircraft weight, commonly expressed in G. Standard-rate turn: approximately 3° of heading change per second. Turn radius: horizontal radius of the flight path in a coordinated turn. Rate of turn: heading change per unit time. Pivotal altitude: the altitude at which a visual reference appears stationary relative to a lateral axis during pivotal maneuvers; the common training estimate depends on groundspeed squared. See the load factor, standard-rate bank, turn radius, and pivotal altitude calculators.
Stall and performance terms
1-G stall speed: stall speed at a load factor of one. Accelerated stall: a stall occurring at a load factor greater than one, so stall speed is higher than the 1-G value. Wing loading: aircraft weight divided by wing area. Power loading: aircraft weight divided by engine horsepower. Dynamic hydroplaning speed: a rule-of-thumb estimate related to tire pressure, not a guarantee of when hydroplaning will begin or end. See the accelerated stall, wing loading, power loading, and hydroplaning tools.
Weight and balance terms
Arm: horizontal distance from the aircraft datum to a station. Moment: weight multiplied by arm. Center of gravity (CG): the balance point represented by total moment divided by total weight. MAC: mean aerodynamic chord. LEMAC: leading edge of the mean aerodynamic chord. Percent MAC: CG position expressed as a percentage of MAC. Ballast: weight added at a known arm to move CG. See the weight and balance builder, moment/CG, percent MAC, and ballast tools.
Distance and coordinate terms
Nautical mile (NM): the standard aviation distance unit, equal to 1,852 meters. DME arc: a curved path flown at an approximately constant DME distance from a station. Great-circle distance: the shortest path between two points on a sphere. DMS: degrees, minutes, and seconds for geographic coordinates. See DME arc distance, great-circle distance, and DMS/decimal conversion.
Mach and atmospheric speed terms
Mach number: true airspeed divided by the local speed of sound. Speed of sound: the propagation speed of small pressure disturbances through air; temperature is a major input. See the Mach number and speed of sound calculators.
Common aviation units
PilotDesk includes conversions for knots, mph, km/h, nautical miles, statute miles, kilometers, pounds, kilograms, U.S. gallons, liters, inHg, hPa, Celsius, Fahrenheit, feet per minute, and meters per second. Use the conversion only after confirming the source unit; the arithmetic can be correct while the answer is wrong if the starting unit was misidentified. Browse the calculator list or the pilot math formula reference.