outward shall be combined with 1⁄2 of the maximum vertical ground reactions obtained in the level landing conditions. (§ 04.2420.) These loads are applied at the ground contact point and may be assumed resisted by the inertia of the airplane. Drag loads may be assumed

zero.

§ 04.243 Taxi and ground handling cases. The landing gear and airplane structure shall be investigated for the following conditions in which the airplane shall be at the design take-off weight. No wing lift shall be considered.

§ 04.2430 Take-off run. The landing gear and airplane structure shall be designed for loads not less than those resulting from the condition specified in § 04.143.

§ 04.2431 Braked roll-(a) Tail wheel type: The airplane shall be assumed in the level attitude with all load on the main wheels. The limit vertical load factor shall be 1.2. A drag reaction equal to the vertical reaction multiplied by a coefficient of friction of 0.8 shall be applied at the ground contact point in combination with the vertical ground reaction. (See Figure 04-11.)

(b) Nose wheel type: The limit vertical load factor shall be 1.2. A drag reaction equal to 0.8 of the vertical reaction shall be combined with the vertical reaction and applied at the ground contact point of each wheel having brakes. Two airplane attitudes shall be considered. (See Figure 04-13.)

(1) The airplane in the level attitude with all wheels contacting the ground assuming zero pitching acceleration and the loads distributed between the main and nose gear by the principles of statics.

(2) The airplane in the level attitude with only the main gear contacting the ground and the pitching moment resisted by angular acceleration.

§ 04.2432 Ground maneuvering.

§ 04.24320 Turning. The airplane in the static position shall be assumed to execute a steady turn by nose gear steering or differential power such that the limit load factors applied at the center of gravity are 1.0 vertically and 0.5 laterally. The side ground reaction at each wheel shall be 0.5 of the vertical reaction. (See Figures 04-12 and 04-14.)

§ 04.24321 Pivoting. The airplane shall be assumed to pivot about one main gear, the brakes on that gear being locked. The limit vertical load factor shall be 1.0 and the coefficient of friction 0.8. The airplane shall be assumed to be in static equilibrium, the loads being applied at the ground contact points. (See Figure 04-15).

(a)

§ 04.24322 Nose wheel yawing. A vertical load factor of 1.0 at the airplane c. g. and a side component at the nose wheel ground contact equal to 0.8 of the vertical ground reaction at that point shall be assumed.

(b) The airplane shall be placed in static equilibrium with the loads resulting from the application of the brakes on one main gear. The vertical load factor at the c. g. shall be 1.0. The forward acting load at the airplane c. g. shall be 0.8 Vm where Vm is the vertical load on one main gear. The side and vertical loads at the ground contact point on the nose gear are those required for static equilibrium. The side load factor at the airplane c. g. shall be assumed

zero.

§ 04.24323 Tail wheel yawing. A vertical ground reaction equal to the static load on the tail wheel, in combination with a side component of equal magnitude shall be assumed. When a swivel is provided, the tail wheel shall be assumed swiveled 90° to the airplane longitudinal axis with the resultant load passing through the axle. When a lock, steering device, or shimmy damper is provided, the tail wheel shall also be assumed in the trailing position with the side load acting at the ground contact point.

§ 04.244 Unsymmetrical loads on dual wheel units. In dual wheel units, 60% of the total ground reaction for the unit shall be applied to one wheel and 40% to the other. To provide for the case of one tire flat, either wheel shall be capable of withstanding 60% of the load which would be assigned to the unit in the specified conditions, except that the vertical ground reaction shall not be less than full static value.

§ 04.25 Water loads. The following requirements shall apply to the entire airplane, but have particular reference to hull structure, wing, nacelles, and float supporting structure.

bottom shall vary in accordance with Figure 04-16. No variation from keel to chine (beamwise) shall be assumed, except when the chine flare indicates the advisability of higher pressures at the chine.

(c) Application of local pressure. The local pressures determined in (a) and (b) shall be applied over a local area in such a manner as to cause the maximum local loads in the hull bottom structure.

§ 04.2511 Distributed bottom pressures. (a) For the purpose of designing frames, keels, and chine structure, the limit pressures obtained from § 04.2510, using a value of W not less than design landing weight, and Figure 04-16 shall be reduced to 1⁄2 the local values and simultaneously applied over the entire hull bottom. The loads so obtained shall be carried into the side-wall structure of the hull proper, but need not be transmitted in a fore-and-aft direction as shear and bending loads.

SA=0.5 VA SMI =Q.5 VMI SM2 =Q5VM

FIGURE 04-12. GROUND TURNING TAIL WHEEL

ΤΥΡΕ.

(b) Unsymmetrical loading. Each floor member or frame shall be designed for a load on one side of the hull centerline equal to the most critical symmetrical loading, combined with a load on the other side of the hull centerline equal to 1⁄2 of the most critical symmetrical loading.

§ 04.2512 Step loading condition—(a) Application of load. The resultant water load shall be applied vertically in the plane of symmetry so as to pass through the center of gravity of the airplane.

(b) Acceleration. The limit acceleration shall be 4.0, unless a lower value is substantiated by suitable tests such as impact basin tests.

(c) Hull shear and bending loads. The hull shear and bending loads shall be computed from the inertia loads produced by the vertical water load. To avoid excessive local shear loads and bending moments near the point of wa

ter load application, the water load may be distributed over the hull bottom, using pressures not less than those specified in § 04.2511.

§ 04.2513 Bow loading condition—(a) Application of load. The resultant water load shall be applied in the plane of symmetry at a point of the distance from the bow to the step and shall be directed upward and rearward at an angle of 30° from the vertical.

(b) Magnitude of load. The magnitude of the limit resultant water load shall be determined from the following equation:

where:

P-2 n, W.

(c) Hull shear and bending loads. The hull shear and bending loads shall be determined by proper consideration of the inertia loads which resist the linear and angular accelerations involved. To avoid excessive local shear loads, the water reaction may be distributed over the hull bottom, using pressures not less than those specified in § 04.2511.

§ 04.2514 Stern loading condition(a) Application of load. The resultant water load shall be applied vertically in the plane of symmetry and shall be distributed over the hull bottom from the second step forward with an intensity equal to the pressures specified in § 04.2511.

(b) Magnitude of load. The limit resultant load shall equal 3⁄44 of the design landing weight of the airplane.

0.5W

VM2 VN

(c) Hull shear and bending loads. The hull shear and bending loads shall be determined by assuming the hull structure to be supported at the wing attachment fittings and neglecting internal inertia loads. This condition need not be applied to the fittings or to the portion of the hull ahead of the rear attachment fittings.

§ 04.2515 Side loading condition—(a) Application of load. The resultant water load shall be applied in a vertical plane through the center of gravity. The vertical component shall be assumed to act in the plane of symmetry and horizontal component at a point half-way between the bottom of the keel and the load waterline at design landing weight (at rest).

(b) Magnitude of load. The limit vertical component of acceleration shall be 3.25 and the side component shall be equal to 15% of the vertical component.

(c) Hull shear and bending loads. The hull shear and bending loads shall be determined by proper consideration of the inertia loads or by introducing couples at the wing attachment points. To avoid excessive local shear loads, the water reaction may be distributed over the hull bottom, using pressures not less than those specified by § 04.2511.

§ 04.252 Float seaplanes.

§ 04.2520 Landing with inclined reactions. The vertical component of the limit load factor shall be 4.0, unless a lower value is substantiated by suitable tests such as impact basin tests. The propeller axis (or equivalent reference line) shall be assumed to be horizontal and the resultant water reaction to be acting in the plane of symmetry and passing through the center of gravity of the airplane, but inclined so that its horizontal component is equal to 4 of its