23.1545—Airspeed indicator.
(a)
Each airspeed indicator must be marked as specified in paragraph (b) of this section, with the marks located at the corresponding indicated airspeeds.
(2)
For the caution range, a yellow arc extending from the red line specified in paragraph (b)(1) of this section to the upper limit of the green arc specified in paragraph (b)(3) of this section.
(3)
For the normal operating range, a green arc with the lower limit at V
S1 with maximum weight and with landing gear and wing flaps retracted, and the upper limit at the maximum structural cruising speed V
NO established under § 23.1505(b).
(4)
For the flap operating range, a white arc with the lower limit at V
S0 at the maximum weight, and the upper limit at the flaps-extended speed V
FE established under § 23.1511.
(5)
For reciprocating multiengine-powered airplanes of 6,000 pounds or less maximum weight, for the speed at which compliance has been shown with § 23.69(b) relating to rate of climb at maximum weight and at sea level, a blue radial line.
(6)
For reciprocating multiengine-powered airplanes of 6,000 pounds or less maximum weight, for the maximum value of minimum control speed, VMC, (one-engine-inoperative) determined under § 23.149(b), a red radial line.
(c)
If V
NE or V
NO vary with altitude, there must be means to indicate to the pilot the appropriate limitations throughout the operating altitude range.
(d)
Paragraphs (b)(1) through (b)(3) and paragraph (c) of this section do not apply to aircraft for which a maximum operating speed V
MO /M
MO is established under § 23.1505(c). For those aircraft there must either be a maximum allowable airspeed indication showing the variation of V
MO /M
MO with altitude or compressibility limitations (as appropriate), or a radial red line marking for V
MO /M
MO must be made at lowest value of V
MO /M
MO established for any altitude up to the maximum operating altitude for the airplane.