There must be enough clearance between the rotor blades and other parts of the structure to prevent the blades from striking any part of the structure during any operating condition.
[Amdt. 27-2, 33 FR 963, Jan. 26, 1968]
source: Docket No. 5074, 29 FR 15695, Nov. 24, 1964, unless otherwise noted.
cite as: 14 CFR 27.661