Fatigue &

Damage Tolerance


Aging Aircraft Support

With the increasing age of both commercial and military aircraft fleets worldwide and latest FAA regulations such as Aging Safety and WFD rules, the necessity for a structural life assurance program is ever more important. Personnel at Avenger have extensive experience in both the analytical methods and implementation of structural integrity programs for a wide variety of aircraft. This includes a thorough knowledge of both military and commercial requirements such as:

–  Air Force Regulation AFGS 87221

–  FAA DTA 25.571

–  FAA Repair Assessment 121.370

–  FAA Aging Safety Rule

–  FAA WFD Proposed Rule

–  FAA Advisory Circular 25.1529

–  FAA Advisory Circular 91-56

–  New FAA Part 26

Analytical Methods

Avenger maintains a staff of qualified, professional technical specialists with extensive experience in performing analyses of aging airframes to the latest regulatory requirements. The basic analytical cornerstones that provide a state-of-the-art structural life assurance program are:

–  Safe Life Analysis

–  Damage Tolerance & Durability Analysis

–  Residual Strength Analysis

–  Fail Safe Analysis

Safe Life Analysis

–  S-N Material Data and Test Correlation

–  Palmgren-Minor Damage Accumulation

–  Load Interaction Fatigue Damage Accumulation

–  Stress Severity Factor Generation

Durability Analysis

Determination of economic life of structure and evaluation to FAA WFD requirements

Fail Safe Analysis

–  Failed Member Assumptions

–  Redistribution of Internal Loads

–  Static Strength Analysis

Residual Strength

Determination of limit load carrying  capacity of structure to include stiffened panels containing varying levels of or lengths of crack

Damage Tolerance Analysis

–  Generation of Flight-by-Flight Stress Spectra

–  da/dN Material Crackgrowth Rate Database

–  Derivation of Stress Intensity Factor (SIF) Solutions

–  Detailed Stress Analysis and FEM capability

–  Crackgrowth Analysis using Linear Elastic Fracture Mechanics

–  Establishment of Inspection Intervals and incorporation into either USAF Force Structural Maintenance Plan (FSMP) or FAA Supplemental Structural Inspection Document

Software Utilized

–  NASA’s NASGRO Crack Growth Code

–  UDRI’s Cracks2000 Crack Growth Code

–  MSC/NASTRAN Finite Element Code

–  Stress Check Finite Element Code

–  AAS’s BoxBeam Internal Load FEM Code

–  AAS’s FLIP Fatigue Load Interaction Code

–  AAS’s SPECGEN Spectrum Code