14 C.F.R. § 29.675
(b) Each stop must be located in the system so that the range of travel of its control is not appreciably affected by—
(d) For each main rotor blade—
(2) There must be means to keep the blade from hitting the droop stops during any operation other than starting and stopping the rotor.
(Secs. 313(a), 601, 603, 604, Federal Aviation Act of 1958 (49 U.S.C. 1354(a), 1421, 1423, 1424), 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. 29-17, 43 FR 50599, Oct. 30, 1978]