Section 25.363 14 CFR Ch. I (1-1-19 Edition) (1) Multiplied by a factor of 1.0 when applied to engine mounts and pylons; and (2) Multiplied by a factor of 1.25 when applied to adjacent supporting airframe structure. [Amdt. 25-141, 79 FR 73468, Dec. 11, 2014] Section 25.363 Side load on engine and auxiliary power unit mounts. (a) Each engine and auxiliary power unit mount and its supporting structure must be designed for a limit load factor in lateral direction, for the side load on the engine and auxiliary power unit mount, at least equal to the maximum load factor obtained in the yawing conditions but not less than - (1) 1.33; or (2) One-third of the limit load factor for flight condition A as prescribed in Section 25.333(b). (b) The side load prescribed in paragraph (a) of this section may be assumed to be independent of other flight conditions. Ho = PAs compartment where, Ho = Maximum opening in square feet, need not exceed 20 square feet. P = (As/6240) + .024 As = Maximum cross-sectional area of the pressurized shell normal to the longitudinal axis, in square feet; and For airplanes with one or more pressurized compartments the following apply: (a) The airplane structure must be strong enough to withstand the flight loads combined with pressure differential loads from zero up to the maximum relief valve setting. (b) The external pressure distribution in flight, and stress concentrations and fatigue effects must be accounted for. (c) If landings may be made with the compartment pressurized, landing loads must be combined with pressure differential loads from zero up to the maximum allowed during landing. (d) The airplane structure must be designed to be able to withstand the pressure differential loads corresponding to the maximum relief valve setting multiplied by a factor of 1.33 for airplanes to be approved for operation to 45,000 feet or by a factor of 1.67 for airplanes to be approved for operation above 45,000 feet, omitting other loads. (3) The maximum opening caused by airplane or equipment failures not shown to be extremely improbable. (f) In complying with paragraph (e) of this section, the fail-safe features of the design may be considered in determining the probability of failure or penetration and probable size of openings, provided that possible improper operation of closure devices and inadvertent door openings are also considered. Furthermore, the resulting differential pressure loads must be combined in a rational and conservative manner with 1-g level flight loads and any loads arising from emergency depressurization conditions. These loads may be considered as ultimate conditions; however, any deformations associated with these conditions must not interfere with continued safe flight and landing. The pressure relief provided by intercompartment venting may also be considered. (g) Bulkheads, floors, and partitions in pressurized compartments for occupants must be designed to withstand [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-23, 35 FR 5672, Apr. 8, 1970; Amdt. 25-91, 62 FR 40704, July 29, 1997] Section 25.365 Pressurized loads. spaschal on DSK3GDR082PROD with CFR (e) Any structure, component or part, inside or outside a pressurized compartment, the failure of which could interfere with continued safe flight and landing, must be designed to withstand the effects of a sudden release of pressure through an opening in any compartment at any operating altitude resulting from each of the following conditions: (1) The penetration of the compartment by a portion of an engine following an engine disintegration; (2) Any opening in any pressurized compartment up to the size Ho in square feet; however, small compartments may be combined with an adjacent pressurized compartment and both considered as a single compartment for openings that cannot reasonably be expected to be confined to the small compartment. The size Ho must be computed by the following formula: 244 VerDate Sep<11>2014 12:50 Apr 30, 2019 Jkt 247046 PO 00000 Frm 00254 Fmt 8010 Sfmt 8010 Y:\SGML\247046.XXX 247046