At the time of the Aloha B.737 incident in 1988 the RAF were operating a large number of relatively high time VC10 aircraft in the Air Transport and Air to Air Refuelling roles. The design of the VC10 is an early example of the 'fail safe' philosophy and incorporates appropriate design features. In addition to the declared design features the Air Registration Board required additional demonstrations of the crack growth characteristics of the VC10 structure. These tests, and others on the wing, fin, fuselage and control surfaces were used to develop additional 'safe life' limits for the aircraft. Circa 1988, however, a series of events combined to prompt a review of VC10 Structural Integrity and in May 1989 it was decided that the VC10 inspection philosophy should disregard the supplementary 'safe life' limits and be re-assessed against the criteria of a wholly damage tolerant regime. For the short term, a programme of structural assurance was devised to fill the 'knowledge gap'; the programme comprised proof pressure testing on the fuselage and a structural sampling programme to inspect the other remaining areas of the airframe. Acoustic Emission testing was used during the fuselage proof pressure test both as an electronic safety measure and as an aid to crack detection. For the longer term, a complete re-analysis of the original fatigue and damage data was initiated, under the auspices of a Fatigue Type Record. To accomplish this review it was necessary to embark upon the production of a complete Finite Element Model for this 40 year old design. This paper describes the migration of the VC10 Structural Integrity philosophy to damage tolerance and expands on some of the problems encountered during this continuing difficult transition period.
展开▼
