A typical VN diagram indicating region of never exceed speed.
The speed beyond which it is not safe to fly an aircraft. It is normally less than the maximum diving speed (VD
). As it concerns rotary-wing aircraft, the never-exceed speed, VNE
, must be established so that it is (i) not less than 40 knots calibrated air speed; and (ii) not more than 0.9 times the maximum forward speeds established, the maximum speed, or the maximum speed substantiated for advancing blade tip Mach number effects, whichever is the least. The VNE
in this case may vary with altitude, RPM, temperature, and weight. The ASI (air speed indicator) is marked with a red radial line at this speed. See also redline condition