S. Kimmins, M.C. Escobedo, P. Rodrigo

A change to §25.571 of the Federal Aviation Regulations (FAR) of the United States (Amendment 96, 30 April 1 998) requires that the inspection threshold for single load path structures and certain types of multiple load path structures should be established based on crack growth analyses and/or tests assuming that the structure contains an initial flaw of the maximum probable size that could exist as a result of manufacturing or service induced damage. This rule will be used as part of the A380 certification. It effectively mandates the use of initial flaws in determining the threshold inspection period. Although the assumed presence of initial flaws in a structure is a normal part of inspection interval determinations, an SN-based approach, supported by test evidence, has been used satisfactorily by Airbus in the past for most structural features. Therefore, the FAR rule represents a departure from normal Airbus practice. This paper reviews the use of initial flaws in damage tolerance calculations and considers the dimensions of the flaw sizes commonly used. The definition of the two common flaw sizes is noted - "rogue flaws" represent unusually poor manufacturing quality and "quality" flaws represent normal manufacturing quality. The definition of the most commonly used sizes for the rogue and quality flaws is open to interpretation and may not be applicable to modern manufacturing practices. An option is allowed for redefining the flaw sizes to represent the concept of "rogue" and "quality" flaw sizes in line with current manufacturing experience. Procedures for doing this are outlined. Evidence for the effect of manufacturing damage on fatigue performance of joints, which a±Iects the definition of the rogue flaw size, has been gathered from recent research programmes, including a European-wide research programme on advanced damage tolerance assessment procedures (ADMIRE).

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

Conference Paper

englisch

A5, 8 Seiten

DGLR-Bericht, 2005, 2005-03, 23rd ICAF Symposium of the international Committee on Aeronautical Fatique - Proceedings; S.189-196; 2005; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

certification, fault tolerance

Bestellbar

2005