Calibrated Airspeed to True Airspeed

def cas2tas(Vcas, H):
    """Calibrated Airspeed to True Airspeed"""
    p, rho, T = atmos(H)
    qdyn = p0*((1.+rho0*Vcas*Vcas/(7.*p0))**3.5-1.)
    Vtas = np.sqrt(7.*p/rho*((1.+qdyn/p)**(2./7.)-1.))
    return Vtas