2.211

2.2110

2.2111

2.2112

approximating or conservatively representing actual conditions.

Symmetrical Conditions (Flaps Retracted). Strength shall be provided for the combinations of airspeed and load factor shown on the V-n diagram of Fig. 2-1, which represents the envelope of the limit loading conditions specified by the maneuvering and gust criteria of 2.2111 and 2.2112.

Airspeeds. The design airspeeds shall be determined as follows: V. (design rough-airspeed) shall not be less than .9Vn, where Vn is the actual high speed at sea level with maximum-except-take-off power. Va (design dive speed) shall not be less than:

1.40 V, (Normal and Transport)
1.50 V, (Training)

1.60 V. (Acrobatic)

Maneuvering Load Factors. The airplane shall be assumed to be subjected to symmetrical maneuvers resulting in the following limit load factors, except that the load factors need not exceed those corresponding to maximum (static) lift coefficients:

(a) The positive maneuvering load factor specified in Fig. 2-2, at all speeds up to Va.

(b) The negative maneuvering load factor specified in Fig. 2-2, at all speeds up to Vr; and factors varying linearly with speed from the specified value at V, to -1.0 at Va.

The specified maneuvering load factors shall be considered as minimum values unless it can be proved that the airplane embodies features of design which make it impossible to develop such values in flight, in which case lower values may be used subject to the approval of the said authorities. (See also 2.131.)

Gust Load Factors. The airplane shall be assumed to encounter symmetrical gusts as specified below:

r

(a) Positive and negative 30 ft/sec. (9.14m/sec.) gusts at V1. The gust load factors obtained at V, shall also be applied at all lower speeds except in the range where load factors are limited by the maximum (static) lift coefficients. (b) Positive and negative 15 ft/sec. (4.572 m/sec.) gusts at Va.

The limit load factors shall be computed by the following formula: KUVa

KUVa

n=1+575 (W/S)

metric: 1+. 57.77 (WS)

where K is the coefficient from Fig. 2-3.

U=gust velocity, feet per second. (m/sec.). (Note that the "effective" sharp edged gust equals KU)

V airplane speed, miles per hour (km/hr.)

a slope of lift curve, CL per radian

W/S=wing loading, pounds per square foot (kg/m.2).

(SEE 2.2112 FOR GUST LOAD FACTOR FORMULA)

FIG. 2-1 LIMIT V-n DIAGRAM

METRIC EQUIVALENTS

CONDITION A, F: V= 14.39/n_(w/s) WHERE W/S = kg/m2

CNA

B: U9.14 m/sec

C,D: U=4.57 m/sec

v = km/hr

[Certain typographical errors in the original have been corrected in this print.-EDITOR.]

FIG. 2-2 LIMIT MANEUVERING LOAD FACTORS

[Certain typographical errors in the original have been corrected in this print.-EDITOR.]

FIG. 2-3 VARIATION OF GUST COEFFICIENT WITH WING LOADING [Certain typographical errors in the original have been corrected in this print.-EDITOR.]

2.212

Symmetrical Conditions (Flaps Deflected). When flaps or other auxiliary high lift devices intended for use at relatively low air speeds are installed, the airplane shall be assumed to be subjected to symmetrical maneuvers and gusts with the flaps fully deflected at the design flap speed, V1, resulting in limit load factors within the range determined by the following conditions:

(a) Maneuvering to a positive limit load factor of 2.0.
(b) Positive and negative 15 feet per second gusts.

2.2120

-T

2.213

2.2130

2.2131

2.2132

2.2133

The design flap speed V, shall not be less than 2V,,, where is the computed stalling speed at sea level with design landing weight and with flaps fully deflected.

V st

Slipstream Effects. In the case of transport category airplanes, suitable investigation of slipstream effects shall be made to insure adequate strength and rigidity of the flap and flap system.

Supplementary Flight Conditions. The following supplementary flight conditions shall be investigated.

Aileron Effects. If the moment coefficient of the airfoil section at zero lift has a positive value, or a negative value smaller than 0.06, the effects of displaced ailerons on the moment coefficient shall be accounted for in the positive portion of the V-n diagram shown on Fig. 2-1.

Unsymmetrical Flight Conditions. To cover possible dissymmetry in loadings, conditions Au, C., and Fu, shall be investigated. These conditions shall be obtained by modifying conditions A, C, and F, respectively, (see Fig. 2-1) as follows:

(a) 100 percent of the specified air load shall be assumed to be acting on one wing and 40 percent on the other.

(b) For airplanes not in the acrobatic category and over 1,000 pounds (453.6 kg.) design take-off weight, the latter factor may be increased linearly with weight up to 80 percent at 25,000 pounds (11,340 kg.).

(c) The unbalanced rolling moment shall be assumed to be resisted by the angular inertia of the complete airplane.

Engine Torque Effects. Engine mounts, nacelles, and the forward portion of the fuselage (when a nose engine is installed) shall also be designed for the following conditions:

(a) The limit torque corresponding to take-off power and propeller speed.

(b) The limit torque from (a) above acting simultaneously with 75 percent of the limit loads from flight condition A (see Fig. 2-1).

(c) The limit torque corresponding to the maximumexcept-take-off power and propeller speed, acting simultaneously with the limit loads from flight condition A (see Fig. 2-1).

The limit torque shall be obtained by multiplying the mean torque by a factor of 1.5 in the case of engines having five or more cylinders. For 4, 3, and 2 cylinder engines, the factors shall be 2, 3, and 4, respectively.

Side Load on Engine Mount. The limit load factor for this condition shall be equal to one third the limit load factor for flight condition A (see Fig. 2-1) except that it shall not be less than 1.33. Engine mounts, nacelles, and the forward portion of the fuselage (when a nose engine is installed) shall be designed for this condition.

2.22 2.220

2.221

2.222

Control Surface Loads

General. The control surface loads shall be assumed to occur in combination with the symmetrical flight conditions (Section 2.211) as described in the following specific control surface loading conditions. Resultant moments about the center of gravity of the airplane shall be reacted in a rational or conservative manner considering the principal masses furnishing the reacting inertia forces.

For conventional control surface and structural arrangements, the specified loading conditions for the respective control surfaces may be assumed to occur independently. End plate (interaction) effects shall be properly accounted for. In the control surface loading conditions described hereinafter, the airloads on the movable surfaces and the corresponding deflections need not exceed those which could be obtained in flight by employing the maximum pilot control forces specified in Section 2.23. In applying this criterion, proper consideration shall be given to the effects of automatic pilot systems, servo mechanisms, and trim tabs in assisting the pilot.

Horizontal Tail Surfaces. The horizontal tail surfaces shall be designed for the following loads:

(a) Maneuvering loads resulting from suddenly pulling the airplane up from steady flight at any point within the limit V-n diagram (Fig. 2-1) to the limit load factor and returning to unaccelerated flight. Acrobatic category aircraft shall be designed for 100 percent unit maneuvering loading on one side of the plane of symmetry and 50 percent on the other. All other categories shall be designed for 100 percent unit maneuvering loading on one side of the plane of symmetry and 70 percent on the other.

(b) Balancing loads necessary to maintain the airplane in equilibrium at any point on the limit V-n diagram.

(c) Gust loads obtained in the symmetrical flight conditions, Section 2.211. The effects of wing downwash may be taken into account.

Vertical Tail Surfaces. Vertical tail surfaces shall be designed for the following loads, independent of the symmetrical flying conditions:

(a) Maneuvering loads resulting from full displacement of the rudder control in straight flight at a speed equal to that at point A on the limit V-n diagram, Fig. 2-1.

(b) For airplanes having propellers not in the plane of symmetry, the speed in paragraph (a) shall not be less than the maximum speed with one engine out of operation.

(c) Gust loads from encountering a gust of 30 feet per second (9.144 m/sec.) intensity normal to the plane of symmetry at speed Vr.

The gust loading shall be computed by the following formula:

W =

KUV a

(metric 57.77)