The temperature that the structure may be exposed to will include maximum and minimum storage, or non-operating, temperatures and maximum and minimum operating temperatures. Note that the temperatures apply to the structure and are derived by reference to external factors. These operating and storage temperatures may not apply to systems and do not account for environmental conditions that may be caused by system operation or may not be applicable as system service conditions. The environmental conditions arising from the effect of the aircraft systems on the structure must be examined and shown not to exceed the limits below:
Hot – Operating Conditions
For most paint colors, a default critical structural temperature of 180oF can be assumed without supporting tests or analyses. Dark colors or black, which may yield higher structural temperatures, are an exception. (PS-ACE100-2001-006, 2001)
Hot – Non-operating Conditions
The accepted limit of hot non-operating conditions can be assumed to be 212F.
Cold – Operating Conditions
The accepted limit for cold operating conditions can be assumed to be -65F.
Cold – Non-operational Conditions
The lowest non-operational temperature that the aircraft could experience is defined by (MIL-HDBK-310, 1997), Table 126.96.36.199.1 as -90F, This shall be adopted as the temperature that the structure should be able to withstand for an indefinite period without compromising structural integrity.
Moisture diffusion analysis and test conditioning should assume a relative humidity on the order of 85 percent as characteristic of past studies from long-term service exposure, which includes ground time in humid environments from around the world. (PS-ACE100-2001-006, 2001)
Note that complete saturation of all laminates in the structure may not be achieved due to the inability of water vapor to penetrate thick laminates. This implies that a blanket knockdown factor for hot/wet for all laminates is conservative for thick laminates. The extent of this conservatism can be determined by test for thick laminates and assemblies as part of the building block test program. Credit can be taken for the increased strength when it is demonstrated to the satisfaction of the certification authority.