In that regard, Brown adds that the MROs have targeted engine models with high-volume shop visits—and parts—that offer the greatest savings potential. Those engines include the General Electric CF6-80, PW4000, CFM56 and International Aero Engines V2500 families. The largest independent MROs have invested heavily in high-tech designated engineering representative (DER) repairs that involve specialized coatings and state-of-the-art brazing and welding.
At Munich-headquartered MTU, many of the new technology insertions are based on new welding, coating and brazing methods, according to Bernd Kriegl, MTU Aero Engine's technical program manager for civil MRO. During 2012, the company spent €160 million (now $216 million) on research and development, of which 10% was for engine component repair processes. While no estimates have been released, Kreigl says the company's R&D investment, and the percentage devoted to engine component repair, should be about the same for 2013. A large number of the company's high-tech repairs are offered under the MTU Plus trademark.
“Some of the key developments have focused on the blades and vanes in the low- and high-pressure compressor sections, including erosion-protection coatings for the airfoils in those parts of the engine,” Kriegl says. “The objective is to maintain a high performance level for the compressors, and increase the life of the blades under harsh, abrasive operating conditions such as desert environments of the Middle East.”
The coatings, Kriegl explains, have led to fuel savings and lower emissions, coupled with greater on-wing time, since entering field trials in 2010. “Their performance throughout the field trials was very favorable, and we are now making them available for customer engine repairs,” he says.
Two years ago, notes Kriegl, MTU also introduced a new tip protection coating for the high-pressure turbine airfoils, which also increases fuel savings. “The tip protects the airfoils from hot-gas corrosion and degradation by enabling the blade to maintain the proper amount of clearance. This is a very unique process using induction-brazing, which has resulted in improved fuel burn, greater component durability, lower emissions and less frequent repairs.”
It also has cut scrap rates, Kriegl adds. “Without the coatings, the scrap rate of the airfoils was about 20%, but with the coatings, it's zero. When the blades or airfoils are overhauled, it's simply a matter of recoating them. They do not need to be scrapped.”
Going forward, he says, research and development will concentrate heavily on engine repair cost reduction by improving and increasing automation used in the processes. “R&D will also be done to reduce the impact of doing repairs on component base material,” Kriegl notes. “And with today's component designs, you also have to implement more advanced welding or brazing processes. That's presenting new challenges.”
For example, he points out that more new-generation engines incorporate integrated blades and discs—often referred to as “blisks,” or an integrated blade and rotor (IBR). The blades, Kriegl explains, do not detach from the disk. “When dealing with blisks or IBRs, there is a much more complex process of repair. MTU is developing proprietary processes and welding technologies to do this kind of work.”
The advanced repairs that Kriegl describes have been designed in-house, and are applicable to turbine engines now in service. MTU Aero Engines—under OEM licenses—specializes in a broad range of Pratt & Whitney and GE products, as well as the V2500, which is estimated to account for one-third of the 1,000 projected engine shop visits to the global MTU network of four shops—Berlin and Hanover in Germany, Vancouver, and Zhuhai, China—for 2013. Some additional growth is expected for 2014, notes Kriegl, although no official estimates are available now.