Aircraft Speeds & Units

Aircraft Speeds Definitions Indicated Air Speed (IAS): The speed read by the pilot on the air speed indicator, corrected for instrument errors. Calibrated Air Speed (CAS): The IAS corrected for the position error of the static port. That position error is greater when flying slow, with flaps down, or when the airplane is in a side slip. Equivalent Air Speed (EAS): The CAS corrected for the error due to the compressibility of the air. That compressibility error is only important when flying at a mach number higher than 0.4. True Air Speed (TAS): The EAS corrected for the relative density of the air.

Distance and Speed Units Nautical mile (nm): Used in air & marine navigation 1 nm = 1,852 m = 6,076 ft Also called air mile or sea mile Unit of flying speed is knot (kt): 1 kt = 1 nm/h = 1.852 km/h Land mile or statute mile = 1,609 m = 5,280 ft