Text in force at 27-51: from 27-0, effective 1 Feb 1965.
(a) Attitudes. Under each of the loading conditions prescribed in paragraph (b) of this section, the rotorcraft is assumed to be in each of the following level landing attitudes:
(1) An attitude in which all wheels contact the ground simultaneously.
(2) An attitude in which the aft wheels contact the ground with the forward wheels just clear of the ground.
(b) Loading conditions. The rotorcraft must be designed for the following landing loading conditions:
(1) Vertical loads applied under Sec. 27.471.
(2) The loads resulting from a combination of the loads applied under subparagraph (1) of this paragraph with drag loads at each wheel of not less than 25 percent of the vertical load at that wheel.
(3) If there are two wheels forward, a distribution of the loads applied to those wheels under subparagraphs (1) and (2) of this paragraph in a ratio of 40:60.
(c) Pitching moments. Pitching moments are assumed to be resisted by--
(1) In the case of the attitude in paragraph (a)(1) of this section, the forward landing gear; and
(2) In the case of the attitude in paragraph (a)(2) of this section, the angular inertia forces.
29 FR 15695 · Source