Flaw IdeNtification through the Application of Loading (FINAL)
Flaw IdeNtification through the Application of Loading (FINAL) involves applying simulated wing loads to the retired F/A-18 Hornet centre fuselage sections, known as centre-barrels (from the US Navy, Royal Canadian Air Force & RAAF) in a test rig.
Loading is of sufficient magnitude and duration to ensure that any existing cracks or defects grow to a size that ensures their detection under laboratory conditions. This is intended to ensure that any potential life-limiting defects not detected through conventional laboratory fatigue testing of a new airframe (e.g. from corrosion, in-service induced mechanical damage, etc.) can be identified in a timely fashion.
The FINAL program was also pivotal to re-evaluation of the estimated life of the centre barrel.
During Hornet certification testing, suspected damage on the one test article was modified or repaired upon detection. By using FINAL these damages where allowed to, grow to failure. In many instances it was found the repairs could have been delayed significantly without compromising the safety of the centre barrel.
The supporting analyses and application of science has lead to a 10% increase in the calculated fatigue life. This has resulted in a reduction in the required numbers of planned fleet centre barrel replacements from 49 to 10. This represented a saving of $400M and a significant increase in aircraft availability.
FINAL is continuing to be used to assess fleet issues as well as advanced repair options.