P-3C aircraft life extension via shape optimisation of holes in lower wing skin stiffeners

Fatigue life extension enhancements to maintain aircraft availability may be required for some circular holes in lower wing skin stiffeners of P-3C Orion aircraft, in service with the RAAF. An appropriate economic option is to rework the holes to precise optimal shapes to minimise the peak stresses, thereby increasing the fatigue life. In this investigation, optimal rework hole shapes for the critical region have been determined. Here DSTO computer codes are utilised in conjunction with commercial finite element software. Full three-dimensional analyses are conducted and it is found that the optimal holes can provide a peak stress reduction of 40%, as compared to the initial holes. © Institute of Materials Engineering Australasia Ltd 2005.