The paper presents a crack growth analysis approach to individual aircraft tracking that will meet the intents and objectives of the U.S. Air Force requirements. The structural life definitions are discussed in terms of definitive crack sizes for both the durability and damage tolerance of the structure.

Instituting a tracking program for a specific aircraft fleet requires a background of data relating to baseline spectra, critical structural locations, and expected airplane usage. The sources of such data are outlined. The body of the paper presents a cost-effective crack growth integration technique which makes tracking for durability feasible even if the life is as much as 100 000 h. Closely linked with the crack growth analysis technique is the method of collecting the flight data. The presentation considers two distinct approaches, a pilot form system and a structural loads measuring system. The methodology is being incorporated into the overall tracking system for the USAF T-39 Utility Trainer which will be the first to use the crack growth principle for both durability and damage tolerance tracking. Some T-39 data are presented for explanatory and demonstration purposes.