Smart repair – big savings

CFM56 split vane repair
Efficient repair developed

Lufthansa Technik has developed a split vane repair that makes it possible to repair the high-pressure turbine (HPT) stators on CFM56 types 5B and 5C extremely efficiently. The only precondition is that one half of the guide vanes must be capable of being repaired in the conventional way. 

A highly cost-effective solution

When taken apart, the HPT vanes on the CFM56 are often found to have sustained serious damage. However, in about 80 percent of cases the problem is confined to one half of the guide vanes. It is here that the split vane repair developed by Lufthansa Technik's Engine Parts and Accessories Repair (EPAR) business unit comes into its own. The repair is time-consuming to perform and requires extremely accurate control of the processes, but the result is a highly cost-effective solution. 

Repair procedure

The first step entails removal of the defective vane segment. After the coating has been stripped and thermo-chemical cleaning performed, the vane remnant is repaired in the conventional manner. The sophisticated part of the repair now starts with soldering of a new replacement part. Special nickel-based high-temperature solders ensure that the join is of the required quality. The soldered part of the vane is then adjusted to the geometry of the remaining piece of the original. This is carried out using a high-performance 5-axis grinding machine that Lufthansa Technik procured specially for the purpose. In addition, the engineers have developed a jig which allows the part to be machined entirely in a single setup, thus guaranteeing the best results.                                                       
After mechanical machining, the repaired part is tested with an airflow check and area measurement to ensure that the original geometry has been adhered to, before its thermal protective coating is then restored. The final stage is EB-PVD coating of the back of the vane.
 

Obvious benefits

A split vane repair costs only one-third as much as a new part. The cost benefits are so significant that Lufthansa Technik now plans to introduce this repair for the HPT vanes of the CFM56-7B. These vanes, which are constructed in 3D Aero geometry, are particularly challenging to repair. But thanks to the procedure outlined above, this hurdle can be mastered.