14 C.F.R. § 29.181 Dynamic stability: Category A rotorcraft.
Title 14 - Aeronautics and Space
Any short-period oscillation occurring at any speed from VY to VNE must be positively damped with the primary flight controls free and in a fixed position. [Amdt. 29–24, 49 FR 44437, Nov. 6, 1984]
Title 14: Aeronautics and Space
PART 29—AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT
Subpart B—Flight
Flight Characteristics
§ 29.181 Dynamic stability: Category A rotorcraft.