§3.270 Pressurized cabins, The strength, detail design, and fabrication of the pressure cabin.

structure shall be evaluated in accordance with the provisions of either paragraph (a) or paragraph (b) of this section. (a) Fatigue strength. The structure shall be shown by analysis and/or tests to be capable of withstanding the repe oads of variable magnitude expected in service. (b) Fail safe strength. It shall be shown by analysis and/or tests that catastrophic failure is not probable after fatigue failure or obvious partial failure of a principal structural element. After such failure the remaining structure shall be capable of withstanding a static ultimate load factor of 75 percent of the limit load factor at Vo» taking into account the combined effect of normal operating pressures, the expected external aerodynamic pressures, and flight loads. These loads shall be multiplied by a factor of 1,15 unless the dynamic effects of failure under static load are otherwise taken into consideration, 7. By amending § 3.343 by inserting after the first sentence a new sentence to read as follows: "Yor secondary control systems including adjustable stabilizers, the system loading in the operation is need not exceed that correaponding to the maximum pilot effort established in accordance with -38. By amending § 3.371 (b) to read as follows: