FAA Federal Aviation Regulations (FARS, 14 CFR)

(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 radial line --

(i) For rotorcraft other than helicopters, at V_NE; and

(ii) For helicopters, at a V_NE (power-on).

(2) A red, cross-hatched radial line at V_NE (power-off) for helicopters, if V_NE (power-off) is less than V_NE (power-on).

(3) For the caution range, a yellow arc.

(4) For the safe operating range, a green arc. (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)))

[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]