Guy Norris/LOS ANGELES
CFM International (CFMI) is being forced to inspect and repair about 200 CFM56-5C4s used on Airbus Industrie A340s after a China Eastern aircraft suffered an in-flight shut down.
The Chinese A340 experienced a first stage high pressure turbine (HPT) blade fracture in the number three engine on climb out from Shanghai in March. The engine was shut down and, after landing, inspections of the remaining powerplants and others in the fleet revealed three more "well over HPT T1 blade axial crack limits".
CFMI confirms that "-we have an issue with the HPT blades on the -5C4, which is limited to the higher gross weight A340s". It adds that there has been a "casting issue resulting in cracking of the trailing edge of the turbine blades, some of which were found under borescope inspection at China Eastern because they are the fleet leader".
Although no other airlines have experienced in-flight shut-downs because of the problem, several have had to inspect and replace engines. Cathay Pacific says it has changed one engine after it "-found a couple of problems". Singapore Airlines, meanwhile, has a programme under way to identify the engines likely to be affected, and says it will be returning them to CFMI for repair.
CFMI, meanwhile, is "-developing a new configuration that should solve the problems". This includes revising the design of the trailing edge slot, to thicken and strengthen it, and tripling the life of the blade. A new thermal barrier coating will also be added. This was developed to combat an unrelated cracking problem on a Gulf Air A340, traced to "oxidation issues" caused by the high temperature operating environment.
The modifications will be made immediately to those engines which have exhibited cracks, while others will go through a "rapid retrofit" programme as they approach 14,000 flight hours.
Source: Flight International