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FIG. 3-5(a) DOWN GUST LOADING ON HORIZONTAL TAIL SURFAC

w AVERAGE UP GUST LOADING (PSF

FIG.

90

40

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3-5(b)-UP GUST LOADING ON HORIZONTAL TAIL SURFACE

30

W-AVERAGE GUST LOADING (PSF)

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W

Sv

40

60

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80

MAXIMUM WEIGHT

AREA OF VERTICAL TAIL SURFACE

FIG. 3-6-GUST LOADING ON VERTICAL TAIL SURFACE

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§ 3.217-1 Gust loads; horizontal tail surfaces (FAA policies which apply to § 3.217).

The specified up gust and down gust load may be carried through the fuselage structure to the wing attachment points, assuming that the fuselage load factor is equal to that given by positive and negative gusts of 30 fps at V. respectively. The angular inertia forces in general produce relieving loads and may be taken into account if desired. The attachments of concentrated mass items in the rear portion of the fuselage may be critically loaded by pitching acceleration forces.

[Supp. 10, 16 F. R. 3287, Apr. 14, 1951] §3.218 Unsymmetrical loads.

The maximum horizontal tail surface loading (load per unit area), as determined by the preceding sections, shall be applied to the horizontal surfaces on one side of the plane of symmetry and the following percentage of that loading shall be applied on the opposite side:

%100-10 (n-1) where:

n is the specified positive maneuvering load factor.

In any case the above value shall not be greater than 80 percent.

VERTICAL TAIL SURFACES

§ 3.219 Maneuvering loads. At all speeds up to V,:

(a) With the airplane in unaccelerated flight at zero yaw, a sudden displacement of the rudder control to the maximum deflection as limited by the control stops or pilot effort, whichever is critical, shall be assumed.

NOTE: The average loading of Figure 3-3 and the distribution of Figure 3-8 may be used unless the Administrator finds it results in unrealistic loads.

(b) The airplane shall be assumed to be yawed to a sideslip angle of 15 degrees while the rudder control is maintained at full deflection (except as limited by pilot effort) in the direction tending to increase the sideslip.

NOTE: The average loading of Figure 3-3 and the distribution of Figure 3-7 may be used unless the Administrator finds it results in unrealistic loads.

(c) The airplane shall be assumed to be yawed to a sideslip angle of 15 degrees

while the rudder control is maintained in the neutral position (except as limited by pilot effort). The assumed sideslip angles may be reduced if it is shown that the value chosen for a particular speed cannot be exceeded in the cases of steady slips, uncoordinated rolls from a steep bank, and sudden failure of the critical engine with delayed corrective action.

NOTE: The average loading of Figure 3-3 and the distribution of Figure 3-9 may be used unless the Administrator finds it results in unrealistic loads.

[21 F.R. 3339, May 22, 1956, as amended by Amdt. 3-3, 23 F.R. 2590, Apr. 19, 1958]

§ 3.219-1 Vertical surface maneuvering loads (FAA policies which apply to § 3.219).

(a) The specified maneuvering loads may be applied to the vertical surfaces and carried through the fuselage structure to the wing attachment points, assuming the lateral inertia load factor along the fuselage structure as zero. The wing drag bracing through the fuselage should be analyzed for this condition since the wings will furnish a large part of the resisting angular inertia. Angular inertia forces on the fuselage may be included if desired.

(1) When the Figures 3-3, 3-7, 3-8, and 3-9 are used to compute the specified maneuvering loads on the vertical tail surfaces, it is not necessary to include the lg balancing load for unaccelerated flight which acts on the horizontal tail surfaces in considering the effects of the vertical tail loads on the fuselage.

(2) When rational methods are used, the maneuvering loads on the vertical tail surfaces and the lg horizontal balancing tail load should be applied simultaneously for the structural loading condition.

[Supp. 10, 16 F. R. 3287, Apr. 14, 1951, as amended by Supp. 21, 20 F. R. 6246, Aug. 26, 1955]

§3.220 Gust loads.

(a) The airplane shall be assumed to encounter a gust of 30 feet per second nominal intensity, normal to the plane of symmetry while in unaccelerated flight at speed V..

(b) The gust loading shall be computed by the following formula:

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below the horizontal surface the critical vertical surface loading (load per unit area) as determined by §§ 3.219 and 3.220 shall be applied:

(a) To the portion of the vertical surfaces above the horizontal surface, and 80 percent of that loading applied to the portion below the horizontal surface,

(b) To the portion of the vertical surfaces below the horizontal surface, and 80 percent of that loading applied to the portion above the horizontal surface.

AILERONS, WING FLAPS, TABS, ETC.

§ 3.222 Ailerons.

Paragraphs (c) through (e) of this section and the note following paragraph (b)(3) of this section shall not be applicable to airplanes for which the Administrator finds them to result in unrealistic loads.

(a) In the symmetrical flight conditions (see §§ 3.183-3.189), the ailerons shall be designed for all loads to which they are subjected while in the neutral position.

(b) In unsymmetrical flight conditions (see § 3.191 (a)), the ailerons shall be designed for the loads resulting from the following deflections except as limited by pilot effort:

(1) At speed Vp it shall be assumed that there occurs a sudden maximum displacement of the aileron control. (Suitable allowance may be made for control system deflections.)

(2) When Ve is greater than Vp, the aileron deflection at Ve shall be that required to produce a rate of roll not less than that obtained in condition (1).

(3) At speed Va the aileron deflection shall be that required to produce a rate of roll not less than one-third of that which would be obtained at the speed and aileron deflection specified in condition (1).

NOTE: For conventional ailerons, the deflections for conditions (2) and (3) may be computed from:

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(c) The critical loading on the ailerons should occur in condition (2) if Va is less than 2Ve and the wing meets the torsional stiffness criteria. The normal force coefficient CN for the ailerons may be taken as 0.048, where 8 is the deflection of the individual aileron in degrees. The critical condition for wing torsional loads will depend upon the basic airfoil moment coefficient as well as the speed, and may be determined as follows: Ts (Cm-.01831) Vď

where:

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(Cm-.01821) V

T/T2 is the ratio of wing torsion in condition (b) (3) to that in condition (b) (2).

821 and 83, are the down deflections of the individual aileron in conditions (b) (2) and (3) respectively.

(d) When T/T. is greater than 1.0 condition (b) (3) is critical; when T1/T1 is less than 1.0 condition (b) (2) is critical.

(e) In lieu of the above rational conditions the average loading of Figure 3-3 and the distribution of Figure 3-10 may be used.

[21 F.R. 3339, May 22, 1956, as amended by Amdt. 3-3, 23 FR. 2590, Apr. 19, 1958]

§ 3.223 Wing flaps.

Wing flaps, their operating mechanism, and supporting structure shall be designed for critical loads occurring in the flap-extended flight conditions (see §3.190) with the flaps extended to any position from fully retracted to fully extended; except that when an automatic flap load limiting device is employed these parts may be designed for critical combinations of air speed and flap position permitted by the device. (Also see §§ 3.338 and 3.339.) The effects of propeller slipstream corresponding to takeoff power shall be taken into account at an airplane speed of not less than 1.4 V. where V, is the computed stalling speed with flaps fully retracted at the design weight. For investigation of the slipstream condition, the airplane load factor may be assumed to be 1.0.

§ 3.223-1 Wing flap load distribution (FAA policies which apply to $3.223).

A trapezoidal chord load distribution with the leading edge twice the trailing edge loading is acceptable. (Note that these loadings apply in the up direction only; however, it is recommended that the supporting structure also be designed

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