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Notes

14 C.F.R. §§ 27.471–27.485

8 sections in range

§27.471. General.

14 C.F.R. § 27.471

(a)
Loads and equilibrium. For limit ground loads—
(1)
The limit ground loads obtained in the landing conditions in this part must be considered to be external loads that would occur in the rotorcraft structure if it were acting as a rigid body; and
(2)
In each specified landing condition, the external loads must be placed in equilibrium with linear and angular inertia loads in a rational or conservative manner.
(b)
Critical centers of gravity. The critical centers of gravity within the range for which certification is requested must be selected so that the maximum design loads are obtained in each landing gear element.
Notes, amendments, and revision history

Authority

Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701-44702, 44704.

Source

Source: Docket No. 5074, 29 FR 15695, Nov. 24, 1964, unless otherwise noted.

§27.473. Ground loading conditions and assumptions.

14 C.F.R. § 27.473

(a)
For specified landing conditions, a design maximum weight must be used that is not less than the maximum weight. A rotor lift may be assumed to act through the center of gravity throughout the landing impact. This lift may not exceed two-thirds of the design maximum weight.
(b)
Unless otherwise prescribed, for each specified landing condition, the rotorcraft must be designed for a limit load factor of not less than the limit inertia load factor substantiated under § 27.725.
Notes, amendments, and revision history

Amendments

[Amdt. 27-2, 33 FR 963, Jan. 26, 1968]

Authority

Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701-44702, 44704.

Source

Source: Docket No. 5074, 29 FR 15695, Nov. 24, 1964, unless otherwise noted.

Amendments

[Amdt. 27-2, 33 FR 963, Jan. 26, 1968]

§27.475. Tires and shock absorbers.

14 C.F.R. § 27.475

Unless otherwise prescribed, for each specified landing condition, the tires must be assumed to be in their static position and the shock absorbers to be in their most critical position.
Notes, amendments, and revision history

Authority

Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701-44702, 44704.

Source

Source: Docket No. 5074, 29 FR 15695, Nov. 24, 1964, unless otherwise noted.

§27.477. Landing gear arrangement.

14 C.F.R. § 27.477

Sections 27.235, 27.479 through 27.485, and 27.493 apply to landing gear with two wheels aft, and one or more wheels forward, of the center of gravity.
Notes, amendments, and revision history

Authority

Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701-44702, 44704.

Source

Source: Docket No. 5074, 29 FR 15695, Nov. 24, 1964, unless otherwise noted.

§27.479. Level landing conditions.

14 C.F.R. § 27.479

(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 § 27.471.
(2)
The loads resulting from a combination of the loads applied under paragraph (b)(1) of this section 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 paragraphs (b)(1) and (2) of this section 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.
Notes, amendments, and revision history

Amendments

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964; 29 FR 17885, Dec. 17, 1964]

Authority

Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701-44702, 44704.

Source

Source: Docket No. 5074, 29 FR 15695, Nov. 24, 1964, unless otherwise noted.

Amendments

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964; 29 FR 17885, Dec. 17, 1964]

§27.481. Tail-down landing conditions.

14 C.F.R. § 27.481

(a)
The rotorcraft is assumed to be in the maximum nose-up attitude allowing ground clearance by each part of the rotorcraft.
(b)
In this attitude, ground loads are assumed to act perpendicular to the ground.
Notes, amendments, and revision history

Authority

Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701-44702, 44704.

Source

Source: Docket No. 5074, 29 FR 15695, Nov. 24, 1964, unless otherwise noted.

§27.483. One-wheel landing conditions.

14 C.F.R. § 27.483

For the one-wheel landing condition, the rotorcraft is assumed to be in the level attitude and to contact the ground on one aft wheel. In this attitude—
(a)
The vertical load must be the same as that obtained on that side under § 27.479(b)(1); and
(b)
The unbalanced external loads must be reacted by rotorcraft inertia.
Notes, amendments, and revision history

Authority

Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701-44702, 44704.

Source

Source: Docket No. 5074, 29 FR 15695, Nov. 24, 1964, unless otherwise noted.

§27.485. Lateral drift landing conditions.

14 C.F.R. § 27.485

(a)
The rotorcraft is assumed to be in the level landing attitude, with—
(1)
Side loads combined with one-half of the maximum ground reactions obtained in the level landing conditions of § 27.479 (b)(1); and
(2)
The loads obtained under paragraph (a)(1) of this section applied—
(i)
At the ground contact point; or
(ii)
For full-swiveling gear, at the center of the axle.
(b)
The rotorcraft must be designed to withstand, at ground contact—
(1)
When only the aft wheels contact the ground, side loads of 0.8 times the vertical reaction acting inward on one side, and 0.6 times the vertical reaction acting outward on the other side, all combined with the vertical loads specified in paragraph (a) of this section; and
(2)
When all wheels contact the ground simultaneously—
(i)
For the aft wheels, the side loads specified in paragraph (b)(1) of this section; and
(ii)
For the forward wheels, a side load of 0.8 times the vertical reaction combined with the vertical load specified in paragraph (a) of this section.
Notes, amendments, and revision history

Authority

Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701-44702, 44704.

Source

Source: Docket No. 5074, 29 FR 15695, Nov. 24, 1964, unless otherwise noted.