Expanded capacity and competence in HPC repair
Engine Parts and Accessories Repair (EPAR)
New repair methods - now available
Like other highly-loaded engine parts, high-pressure compressor (HPC) components suffer from deterioration over time. The engineers in the Engine Parts and Accessories Repair (EPAR) division have taken a close look at the HPC vanes of the CF6-80 and the CFM56. The result: New, more extensive repair methods are now available for the variable stator vanes of these two popular engine types.
CF6-80C2 platform repair: A world first
A new repair for the CF6-80C2 high-pressure compressor vanes (variable stator vanes) does not only entail the trunnion, but comprises the platform as well. After extended engine operation, the platforms and trunnions of the variable stator vanes of the CF6-80C2 high pressure compressor tend to wear at the contact surfaces. In the past, the repair of damaged trunnions was already available. Unfortunately this was not an actual solution to the problem, as damage to the platforms is the critical item: If wear on the platforms is more than 0.12 mm (0.005 inches), the engine manual requires the vanes to be scrapped and replaced. The engineers at Lufthansa Technik's Engine Parts and Accessories Repair division have now put an end to this situation: By using a specially developed version of High Velocity Oxygen Fuel Coating (HVOF), the repair for the trunnion has been extended beyond the scope of the Manual Repair. As the platform and trunnion have similar physical and mechanical properties, it was reasonable to apply a similar repair on the platform.
With the new repair, for which Lufthansa Technik has been granted EASA and FAA DER approvals, the thermal spray process is extended to the platform area, so that damage on both surfaces may be repaired with this process. An HVOF method was chosen due to the superior material properties achieved with this process, properties which are now equal to those of the new part. With this process, platform surface wear of up to 0.51 mm (0.02 inches) may be repaired, meaning that nearly 70 percent of all affected parts can be repaired, thus avoiding scrapping.
Friction welding of CFM56 VSV trunnion
Variable stator vanes in the first three stages of the high pressure compressor of CFM56 engines often sustain damage to the threaded part of the outer trunnion. With a proprietary repair Lufthansa Technik manages to restore damaged parts to their original condition. EASA and FAA approvals have been obtained. For a number of reasons, with mishandling due to the exposed position of the part among them, the threaded part on the outer trunnion of HPC variable stator vanes often shows damage during an engine overhaul. In such cases, the engine shop manual leaves no doubt: The affected part must be exchanged. From today, an alternative solution is available: A new repair process developed by Lufthansa Technik's EPAR engineers avoids the exchange of the entire vane by replacing the trunnion part only, thus constituting a more economical path.
The new HPC repair processes not only offer customers repair solutions for high-pressure compressors that are superior both technically and economically. They also underline the strengths of the Engine Parts and Accessories Repair divison in finding economic solutions, where other MRO providers have to resort to buying a replacement part. Thus they are the embodiment of Lufthansa Technik's philosophy: Supporting its customers by providing high-value, economic repairs.