Probabilistic Damage Tolerance Analysis for General Aviation

The General Aviation (GA) fleet includes about 150,000 airplanes that were certified with no fatigue evaluation requirements. The average age of these airplanes is about 40 years, and many are high-time. To mitigate the aging effects on the GA fleet, a probabilistic damage tolerance analysis (PDTA) program has been developed. A PDTA approach also provides a mechanism whereby inspection and maintenance operations can be included into the simulation, thus providing engineers the opportunity to assess the benefits of maintenance actions. This paper describes the probabilistic methodology to be utilized in a computer software program (SMART vertical bar DT) that performs risk assessment of small airplanes employing NASGRO (R) or a user selected code as the crack growth engine. The methodology can assess a range of random variables, calculate the extreme value distribution (EVD) of maximum stress per flight from a general aviation (GA) spectrum, and generate a surrogate model for accurate and fast calculations of crack grow. The main objective is to develop a comprehensive probabilistic methodology such that engineers can conduct a risk assessment of GA structural issues in support of policy decisions.