Delta Air Lines’ Technical Operations (TechOps) maintenance arm is pushing a raft of new engine overhaul and repair technology as part of efforts to cut costs and boost revenue.

“There is a consistent tug and pull between users and original equipment manufacturers (OEMs) these days, and airlines like Delta are investing in the ability to do more of this [sophisticated engine inspection and repair] on their own,” says David Garrison, Delta TechOps engine and component maintenance managing director.

Delta’s current total maintenance expenses are about $1.8 billion per year, divided roughly equally between material costs and outside repairs. Engines account for the lion’s share with some $1.1 billion, while components, such as line-replaceable units, make up $300 million and base operations and line maintenance the rest.

With Delta placing extra focus on reducing outside costs as part of initiatives to offset the rising cost of fuel, TechOps is evaluating new ways of reducing engine maintenance costs. “Let’s break some of the paradigm which is the traditional way of working through the OEMs,” Garrison told the Joint Propulsion Conference in Atlanta. “We’ve invested in our ways to inspect blades and perform other tasks. Some airlines . . . prefer to deal with the OEMs on everything, but I’d encourage us to look at the options.”

Delta TechOps runs the largest engine shop in North America and one of the largest in the world, with more than 700 repair events on 12 engine types from four engine OEMs. “We put through roughly 700 engines per year for Delta and other customers,” says Garrison, adding that improvements in control parts flow and management has seen Pratt & Whitney JT8D-219 overhaul and repair turn time reduced to almost 10 days versus 33 in early 2008. Overall engine repair and support turn time has similarly reduced from 14 days in 2008 to a current average of 7.5 days, or virtually a 50% improvement. “By increasing turn time we saved over $100 million over three years,” he adds.

The airline is looking to increase these savings by taking spare engines “that we created using this extra turn time speed and parting them out for spares,” says Garrison. This means that instead of stocking additional spares, or even buying in additional engines, “we feed ourselves, rather than bringing in new spares.”

New technology initiatives include the introduction of a technique called process compensated resonance testing, which is being used successfully to detect potential flaws in turbine blades ahead of in-service failures. The system uses bench testing to excite parts to known frequencies and compares the results against a database derived from earlier tests of OEM parts. “We’ve taken brand-new OEM parts with no defects to get a good baseline; then we run parts which we know have been through events such as over temps. This is used to develop a database, and that gives the mechanic a go no-go response.”

Garrison adds TechOps is “looking at implementing the process on the Pratt & Whitney PW4000 and PW2000 turbine because we’ve had some issues.” In service to-date, the system has helped the airline dramatically decrease the inflight shutdown and other failure rate of the JT8D fleet on the MD-80. “The resonance response was applied to the JT8D-219 first stage T1 turbine blades after we had a rash of failures,” he adds.

The airline also is looking at introducing a low plasticity burnishing process that “allows us to apply stress compressing of parts,” says Garrison. The system uses a high hardness ball rolled under pressure over low-pressure spool parts to improve service life and extend time-on-wing. TechOps also uses a Barkhausen noise inspection system to improve inlet reliability, and is discussing new erosion-resistant coating treatments for compressor airfoils with the OEMs.

“It creates an interesting conversation with General Electric,” says Garrison, adding that repair and replacement costs for a 13-stage compressor “can add up quickly.” The treatment provides an exhaust gas turbine margin benefit, reduces scrap rates and generates up to a 0.5% specific fuel consumption improvement, but takes away a source of valuable after-market revenue for the OEM.