Some reports of cracks in A-frame columns were first received in
mid-1999 after some 5000 to 12 000 running hours. A project team
was established to investigate the matter and all other engines in
service were inspected. Although the cracks occurred in seven of the
eight engines, they were in only some of the double-walled A-frame
columns manufactured to the original design, and were of various
degrees of severity. The cracks were initiated at the inboard ends of
two pairs of horizontal ribs on the columns and propagated vertically
and in the direction of the crosshead guide rails. The root of the
problem was a combination of lack of welding quality and somewhat
higher than anticipated local stress level