Widespread Fatigue Damage in Military Aircraft (L'endommagement en Fatigue des Avions Militaires).
Abstract
A structure potentially susceptible to Widespread Fatigue Damage (WFD) is defined by the Industry Committee on Widespread Fatigue Damage, as a structure which has the characteristics of similar features operating at similar stresses where structural capability could be affected by similar cracking. The well-publicized 1988 incident of the Aloha Airlines Boeing 737, which lost a large section of fuselage structure in flight, ushered in the era of research into ageing aircraft. This incident was caused by a collinear series of fatigue cracks which suddenly linked to form a single critical crack, leading to the catastrophic failure. At the time of the Aloha incident, a large number of relatively high-life military aircraft were in service, mainly in the roles of air transport, air-to-air refueling and maritime reconnaissance. Maintaining the structural integrity of these aircraft in prolonged service requires consideration to be given to inspections for detecting possible multiple damage in its various forms: 'Multi-site' damage (MSD) occurs mainly on neighbouring elements (lines of attachment holes, for example) or as a result of a fabrication surface damage (a long, continuous, scratch, for example). Their coalescence can lead to a sudden loss of residual strength. The concept of 'resistance to damage' implies structures which are able to tolerate the presence of cracked elements by ensuring that cracks are slowly propagated and to tolerate the presence of broken elements by providing load path redundancy. On this basis, the strength of the remaining undamaged structure must be sufficient to ensure safety in flight during a specified operating period. The role of Damage Tolerance is to assure structural integrity through in-service directed inspections of critical structures.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1995
- Accession Number
- ADA303784
Entities
Organizations
- AGARD