The fail safe characteristics of this structure, i.e., the ability to fail panel ­ and fly safely until the failed panel is detected, depends upon the residual strength capability at the time of and subsequent to load path failure and the capability of and frequency of in-service inspections.  The remaining structure guidelines are specified in JSSG-2006 paragraph A3.12.2.2. 

As stated earlier, the fail safety will be supported by walk-around-visual inspections for damage sizes on the order of a failed load path.  Generally, the walk-around-visual inspection can be aided by detectable signs such as fuel leakage.  At any rate, the minimum inspection capability for this example will be considered to be a failed load path.

The damage as illustrated in Figure 1.3.17 shall not grow to a size such as to cause loss of the wing due to the application of P_VW in 5 times the inspection interval (10 flights), i.e. in 50 flights.  This is illustrated in Figure 1.3.20.  The load P_xx = P_yy will generally be less than the design limit condition and P_yy (as discussed in Section 2.5) will always be equal to or greater than that associated with the design limit condition.

Figure 1.3.20.  Illustration of Damage-Growth Limits and Strength Guidelines; Remaining Structure Subsequent to Load-Path Failure