L. Molent, B. Dixon, S. Barter, J. Medved, Q. Nguyen

The teardown and inspection of high life aircraft is a central requirement of many Aircraft Structural Integrity Programs (ASIP). There are many reasons for this including the need to inspect for the potential onset of wide spread fatigue damage and to assess the impact of corrosion and in-service mechanical damage. Furthermore, service life data from fleet aircraft are required to confirm the fatigue test results and corroborate the assumptions made during service life calculations or probabilistic risk and reliability studies. To achieve these goals for the RAAFs F/A-18 fleet a teardown and inspection of the fracture critical F/A-18 wing attachment bulkheads (or centre barrel - CB) has been initiated. Use is being made of ex-service, fatigue-life expended, CBs supplied from the Canadian Forces and USNs CB replacement programs. This program is known as the Flaw IdeNtification through the Application of Loads (FINAL) program. This paper presents an argument that, regardless of the structural design philosophy of the aircraft, the largest "likely" cracks in well-designed critical fighter structure will be less than 1 mm deep at the time it is normally removed from service. Since the crack depth threshold for the reliable detection of cracks for current NDI methods (for instance high frequency eddy current (HFEC) detection) is 1.0 mm or greater, these cracks may not be found during conventional teardown. To significantly improve the probability of detecting cracks that are below the lower threshold of NDI, an increase in their size by accelerated fatigue testing of the CBs has been implemented. Cyclic loads (using the mini-FALSTAFF spectrum) are applied to the wing attachment lugs of ex-service CBs in a test rig to simulate in-flight wing loads. The loading is of sufficient magnitude and duration to ensure that any existing cracks will be grown to a size that ensures their detection under laboratory conditions. Quantitative fractography has been performed on observed cracks to obtain crack growth data and to determine the size, nature and cause of discontinuities that initiate fatigue cracking. This paper will provide a summary of the teardown philosophy, methodology and preliminary results. The process elaborated here should be applicable to other aircraft.

23rd ICAF Symposium of the international Committee on Aeronautical Fatique, 2005, Hamburg

Conference Poster

englisch

A5, 14 Seiten

DGLR-Bericht, 2005, 2005-03, 23rd ICAF Symposium of the international Committee on Aeronautical Fatique - Proceedings; S.669-682; 2005; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

crack growth, f/a-18 aircraft, aircraft teardown

Bestellbar

2005