14 C.F.R. § 27.411 Ground clearance: tail rotor guard.
Title 14 - Aeronautics and Space
(a) It must be impossible for the tail rotor to contact the landing surface during a normal landing. (b) If a tail rotor guard is required to show compliance with paragraph (a) of this section— (1) Suitable design loads must be established for the guard; and (2) The guard and its supporting structure must be designed to withstand those loads.
Title 14: Aeronautics and Space
PART 27—AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT
Subpart C—Strength Requirements
Control Surface and System Loads
§ 27.411 Ground clearance: tail rotor guard.
