(a) The never-exceed speed VNE must be established so that it is--
(1) Not less than 0.9 times the minimum value of VD allowed under Sec. 23.335; and
(2) Not more than the lesser of--
(i) 0.9 VD established under Sec. 23.335; or
(ii) 0.9 times the maximum speed shown under Sec. 23.251.
(b) The maximum structural cruising speed VNO must be established so that it is--
(1) Not less than the minimum value of VC allowed under Sec. 23.335; and
(2) Not more than the lesser of--
(i) VC established under Sec. 23.335; or
(ii) 0.89 VNE established under paragraph (a) of this section.
(c)(1) Paragraphs (a) and (b) of this section do not apply to turbine airplanes or to airplanes for which a design diving speed VD/MD is established under Sec. 23.335(b)(4). For those airplanes, a maximum operating limit speed (VMO/MMO airspeed or Mach number, whichever is critical at a particular altitude) must be established as a speed that may not be deliberately exceeded in any regime of flight (climb, cruise, or descent) unless a higher speed is authorized for flight test or pilot training operations.
(1) Paragraphs (a) and (b) of this section do not apply to turbine airplanes or to airplanes for which a design diving speed VD/MD is established under Sec. 23.335(b)(4). For those airplanes, a maximum operating limit speed (VMO/MMO airspeed or Mach number, whichever is critical at a particular altitude) must be established as a speed that may not be deliberately exceeded in any regime of flight (climb, cruise, or descent) unless a higher speed is authorized for flight test or pilot training operations.
(2) VMO/MMO must be established so that it is not greater than the design cruising speed VC/MC and so that it is sufficiently below VD/MD, or VDF/MDF for jets, and the maximum speed shown under Sec. 23.251 to make it highly improbable that the latter speeds will be inadvertently exceeded in operations.
(3) The speed margin between VMO/MMO and VD/MD, or VDF/MDF for jets, may not be less than that determined under Sec. 23.335(b), or the speed margin found necessary in the flight tests conducted under Sec. 23.253. [Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as amended by Amdt. 23-7, 34 FR 13096, Aug. 13, 1969; Amdt. 23-62, 76 FR 75762, Dec. 2, 2011]