DISTRIBUTION A. Approved for public release; distribution unlimited.
EN-SB-12-003, Page 1 of 8
Number: EN-SB-12-003
Date: 19 July 2012
Subject: Damage Tolerance Inspection Methodology for Slow Crack Growth
Metallic Structure
References:
1. Department of Defense Joint Service Specification Guide, Aircraft Structures,
JSSG-2006, 30 October 1998.
2. Department of Defense Standard Practice, Aircraft Structural Integrity Program,
MIL-STD-1530C, 1 November 2005.
3. Structures Bulletin, Revised Damage Tolerance Requirements for Slow Crack
Growth Design Concepts for Metallic Structures, EN-SB-08-002, Rev A, 18 March
2011.
4. Structures Bulletin, Nondestructive Inspection Capability Guidelines for United
States Air Force Aircraft Structures, EN-SB-08-012, Rev. B, 11 July 2011.
5. USAF Damage Tolerant Design Handbook: Guidelines for the Analysis and Design
of Damage Tolerant Aircraft Structures, AFRL-VA-WP-TR-2003-3002, November
2002.
Background:
Reference 1 contains damage tolerance requirements for design of military airframe
structures. This guidance provides initial flaw size assumptions, continuing damage
criteria, and in-service flaw size assumptions, as well as a requirement that inspections
be conducted at one-half of the calculated time it takes for an assumed flaw to grow to a
critical size. Reference 2 provides additional clarification regarding the establishment of
initial and repeat inspection intervals for slow damage growth designs. Additionally,
Reference 3 provides revised damage tolerance requirements for slow crack growth
structure in addition to revised continuing damage flaw sizes. Finally, Reference 4
contains nondestructive inspection (NDI) capability values that provide recommended
Structures Bulletin
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