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DTD Handbook

Handbook for Damage Tolerant Design

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    • Sections
      • 1. Introduction
        • 0. Introduction
        • 1. Historical Perspective on Structural Integrity in the USAF
        • 2. Overview of MIL-HDBK-1530 ASIP Guidance
        • 3. Summary of Damage Tolerance Design Guidelines
          • 0. Summary of Damage Tolerance Design Guidelines
          • 1. Summary of Guidelines
          • 2. Design Category
          • 3. Inspection Categories and Inspection Intervals
          • 4. Initial Damage Assumptions
          • 5. Residual Strength Guidelines
          • 6. Required Periods Of Safe Damage Growth
          • 7. Illustrative Example Of Guidelines
            • 0. Illustrative Example Of Guidelines
            • 1. Slow Crack Growth Structure
            • 2. Fail Safe Structure
              • 0. Fail Safe Structure
              • 1. In-Service Inspection Consideration
              • 2. Initial Flaw Considerations
              • 3. In-Service Flaw Assumptions Following Inspection
              • 4. Adjacent Structure Damage Following the Failure of the Major Load Path
              • 5. Analysis of Intact Structure–Residual Strength Guidelines and Damage Growth Limits
              • 6. Analysis of Intact Structure (Alternate Requirement)
              • 7. Discussion of Intact Structure Analysis
              • 8. Analysis of Remaining Structure Subsequent to Load Path Failure
              • 9. Derivation of Residual Strength Load
              • 10. Incremental Damage Growth Da
              • 11. Alternative-Analysis of Remaining Structure Subsequent to Load Path Failure
              • 12. Summary and Comments
        • 4. Sustainment/Aging Aircraft
        • 5. References
      • 2. Fundamentals of Damage Tolerance
      • 3. Damage Size Characterizations
      • 4. Residual Strength
      • 5. Analysis Of Damage Growth
      • 6. Examples of Damage Tolerant Analyses
      • 7. Damage Tolerance Testing
      • 8. Force Management and Sustainment Engineering
      • 9. Structural Repairs
      • 10. Guidelines for Damage Tolerance Design and Fracture Control Planning
      • 11. Summary of Stress Intensity Factor Information
    • Examples

Section 1.3.7.2.0. Fail Safe Structure

This example of fail safe structure is based on the lower wing structure shown in Figure 1.3.11.  The structure is assumed to be a Fail Safe Multiple Load Path Structure and the steps required to satisfy this requirement will be outlined.  The structure will be designed to be Fail Safe by virtue of being able to sustain the failure of one major load path or skin panel and still maintain the residual strength and remaining structural guidelines.  For illustration purposes, panel ­ was chosen as the critical load path.  Although the loss of panel ­ is critical from a remaining structure point of view, every panel must be designed to meet the intact guidelines.