China Airlines Flight 611, operated by a Boeing 747-200, was at the top of its take-off climb over Penghu Islands off Taiwan on 25 May 2002 when fatigue failure of the rear part of its fuselage occurred.
This area of the 747-200 had been repaired with the application of a large rectangular doubler measuring 610 x 300mm (2 x 10ft) at at the upswept rear portion of the fuselage. Corrosion was evident and corrosion-induced cracks had initiated at, and propagated from corrosion pits.
Of particular concern is the continued adherence by this airline to conduct fuselage maintenance activities at roughly four-yearly intervals - in other words, as the aircraft gets older, any cracks that have occurred will continue to grow and probably at an increasing rate.
Therefore, from a safety of flight viewpoint it is essential that as each aircraft ages (this one was 23 years old), these critical-to-flight inspections must be conducted on a progressively shortened inspection interval frequency. To do this, sufficient fatigue test results must be available before the start of airline service. This data must be obtained either from material specimen tests and/or fatigue life results from testing fuselage portions with climatic conditions applied. The bottom line, however, is that this aircraft passed a heavy maintenance inspection yet was structurally unsound. A reduction in the maintenance interval might well have prevented this accident. Fatigue is insidious, especially in a corrosive environment. If you do not find it - it will find you.
Trevor Jarvis Marblehead, Massachusetts, USA
Source: Flight International
