Under FAR Part 25, a factor of safety is applied unless specified otherwise in terms of which loading condition?

The correct choice regarding the application of a factor of safety under FAR Part 25 is ultimate loads. This is because the regulations typically stipulate that a factor of safety must be applied to ensure the structural integrity and performance of an aircraft during various loading conditions.

Ultimate loads are defined as the maximum load that a structure can withstand before failure occurs. The factor of safety applied to ultimate loads ensures that there is a buffer between the loads that an aircraft structure experiences during flight and the loads that will cause failure. By designing structures to withstand forces greater than those they would normally encounter under operating conditions, safety and reliability are significantly enhanced.

In contrast, applied loads and limit loads represent different stages in the assessment of structural integrity. Applied loads refer to the actual loads acting on a structure during normal operation, while limit loads are defined as the maximum loads expected to occur during operational conditions without failure. The factor of safety typically does not apply to limit loads in the same way as it does to ultimate loads, since limit loads are often already predicated on the understanding that operational scenarios should remain safely below failure thresholds. Therefore, it is the context of ultimate loading conditions that necessitates the explicit stipulation of a factor of safety under these guidelines.