§3.47 Structural terms.

Structure: Those portions of the airplane the failure of which would seriously endanger the safety of the airplane. Design wing area, S: The area enclosed by the wing outline (including ailerons, and flaps in the retracted position, but ignoring fillets and fairings) on a surface containing the wing chords. The outline is assumed to extend through the nacelles and fuselage to the centerline of symmetry. Aerodynamic coefficients: CL, CN, CM, etc., used in this part, are nondimensional coefficients for the forces and moments acting on an airfoil, and correspond to those adopted by the United States National Advisory Committee for Aeronautics. CL = airfoil lift coefficient. CN = airfoil normal force coefficient (normal to wing chord line). et or structural members, "fire-resistant" material CNA = airplane normal force coefficient (based on lift of complete airplane and design wing area). CM = pitching moment coefficient. Loads Reference Sections Limit load: The maximum load anticipated in service. 8.171 Ultimate load: The maximum load which a part of structure must be capable of supporting. 8.173 Factor of safety: The factor by which the limit load must be multiplied to establish the ultimate load. 8.172 Load factor or acceleration factor, n: The ratio of the force acting on a mass to the weight of the mass. When the force in question represents the net external load acting on the airplane in a given direction, n represents the acceleration in that direction in terms of the gravitational constant. Limit load factor: The load factor corresponding to limit load. Ultimate load factor: The load factor corresponding to ultimate load.