Helicopter true airspeed calculatorDescriptionThis calculator estimates the true airspeed (KTAS) of a helicopter. True airspeed is the speed of a helicopter relative to the surrounding, undisturbed air. If there's no wind, true airspeed equals the speed relative to the ground (groundspeed). However, if a helicopter is flying north, and a 10kt wind is blowing from the north, the true airspeed will be 10kt greater than the groundspeed. Dynamic pressure measurements outside an aircraft are used to estimate indicated airspeed. This airspeed generally differs from true airspeed because it's biased by atmospheric properties and local flow deviations due to things like rotor wash. EquationsThe following equations are used to estimate true airspeed. \[ m_s = KCAS/c_0 \] \[ T_R = T / T_0 \] \[ P_R = ( \frac{T_0 + \delta P_A}{T_0} )^{5.2559} \] \[ KTAS = c_0\sqrt{5 T_R ((\frac{(m_s^2/5+1)^{7/2}-1} {P_R} +1)^{2/7}-1) } \]Many symbols are defined in Helicopter Abbreviations and Symbols. In addition, we use the following symbols here.
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