Page 17 of this PDF is interesting...
However it has to be said that with the engine having a TT in the region of 10000 hours, it suprises me it still hangs together. Especially with the UK CAA allowing a 3000hr TBO for public transport operations, in this aircraft.
Also intresting is that the aircraft could not hold altitude (5500ft) with the prop not feathered on just one of the 3 engines.
The stud failure was apparently caused by lack of cadmium plating coverage, corrosion and high cycle fatigue. To me, this is a reminder not to run cylinder studs through 4 or 5 overhaul cycles before replacement, and to make sure all the studs are re-plated at any overhauls prior to replacement.
The history of the overhauls on this engine, who did them and what kind of overhauls, would be of interest to me if I were researching this failure. Overhauls can vary in quality, level of parts replacement etc, and this engine had logged an almost unbelievable 11,992 hrs total time. That's a lot of overhauls, and my guess would be that the cylinder studs had never been replaced, and possibly never replated. Although a quality overhaul would include sending all the fasteners to be cad plated, it's harder to find suitable suppliers now due to environmental regulations on plating shops.
