Some factors influencing damage tolerance under helicopter spectra

The design of helicopter structural components has been based principally on the safe life design approach, although in the last two decades there has been increasing use of damage tolerance methodologies which focus explicitly on the progressive change in structural risk with time. However, the benefits to a fleet in terms of cost, safety, and fleet management, of using damage tolerant design over a structure designed using a safe life design approach, are still subject to some debate. This paper focuses on the comparison of analytical results from damage tolerance and safe life approach on a hypothetical component under a real helicopter spectrum. The load spectrum is reconstituted from data from the Black Hawk helicopters in use with the Australian Defence Force, using two methods; namely peak-valley reconstitution and reverse rainflow reconstitution. The effect of the reconstitution method on the life analyses is also explored.