(a) Each airspeed indicator must be marked as specified in paragraph (b) of this section, with the marks located at the corresponding indicated airspeeds.(b) The following markings must be made:(1) A red line: (i) For rotorcraft other than helicopters, at VNE.(ii) For helicopters, at VNE (power-on).(iii) For helicopters, at VNE (power-off). If VNE (power-off) is less than VNE (power-on) and both are simultaneously displayed, the red line at VNE (power-off) must be clearly distinguishable from the red line at VNE (power-on).(3) For the caution range, a yellow range.(4) For the normal operating range, a green or unmarked range.Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as amended by Amdt. 29-15, 43 FR 2327, Jan. 16, 1978; 43 FR 3900, Jan. 30, 1978; Amdt. 29-17, 43 FR 50602, Oct. 30, 1978; Amdt. 29-59, 88 FR 8740, Feb. 10, 2023 Secs. 313(a), 601, 603, 604, and 605 of the Federal Aviation Act of 1958 (49 U.S.C. 1354(a) , 1421 , 1423 , 1424 , and 1425 ) ; and sec. 6(c), Dept. of Transportation Act (49 U.S.C. 1655(c)