Aircraft Risk Analysis 

Southwest Research Institute® (SwRI®) structural engineering specialists use probabilistic methods to perform risk assessments to quantify the safety and useful service life of aircraft structures in terms of probability of failure and hazard rate. These analyses evaluate alternative usage, maintenance, and inspection scenarios in terms of safety-of-flight risk and can be used to make planning decisions by balancing safety, cost and readiness of the aircraft system.

SwRI engineers use analysis tools such as the USAF probability of fracture (PROF) software and other advanced probabilistic methods contained in SwRI’s NESSUS® and DARWIN® software to assess the effects of variabilities and uncertainties in loadings, material properties, fatigue and fracture models, flaw sizes, and inspection methods on the risk of structural failure.

Capabilities

• Risk evaluations of in-service cracking
• Evaluation of safety and economic impacts of service life extensions
• Risk-based evaluations of inspection, repair and/or modification plans
• Single aircraft and fleet-wide risk analyses
• Development of random variable probabilistic distributions for risk analyses
• Probabilistic fatigue and fracture analyses
• Equivalent Initial Flaw Size (EIFS) distribution development using in-service cracking and teardown data
• Probability of Detection (POD) curve development for nondestructive inspection methods
• Interpretation of risk analysis results in terms of MIL-STD-882D and JSSG-2006
• Economic life evaluations
• Sensitivity studies
• Risk assessment workshops and training

Single-flight probability of failure (SFPOF) results with and without recurring inspections

Experience

• Damage Tolerance Risk Assessment of T-38 Wing Skin Cracks
• Risk Assessment of T-37B Fatigue Critical Locations
• Risk Assessment of the A-10 Wing Aft Lower Cover at Rear Spar Cap (WS 23)
• Risk and Economic Implications of DADTA for F-5 Foreign Operators
• Probabilistic Structural Analyses of Fatigue and Fracture
• Advanced Probabilistic Fracture Mechanics & Life Evaluations of Turbine Rotor Blade Attachments

SwRI performs risk analyses of in-service cracking detected in aircraft structures

Analysis Tools for Risk Assessment

• PROF
• DARWIN®
• NESSUS®
• Weibull Analyses

SFPOF for recurring inspections and different detectable flaw sizes

This flyer was published in September 2007. For more information about Aircraft Risk Analysis, contact Joseph W. Cardinal, Staff Engineer, Phone (210) 522-3323, Fax (210) 522-3042, Mechanical and Materials Engineering Division, Southwest Research Institute, P.O. Drawer 28510, San Antonio, Texas 78228-0510.

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