It is unknown which of these airlines, if any, have installed or intend to install the Enhanced Performance, or EP, Trent kit, which incorporates many of the features of the EP standard for new-build 700s that R-R introduced three years ago. R-R does not identify which customers bought the retrofit kit, although the enginemaker reports that 12 carriers so far have purchased it.
Though the EP kit does not turn the older Trent 700 into today’s build, it comes pretty close. Like the new-build engine, the EP kit features the aerodynamically enhanced compressor blade shape R-R developed for the latest Trent 1000 and Trent XWB engines. Elliptical leading edge profiles improve efficiency for these blades, which are installed on all of the engines’ intermediate- and high-pressure compressor blades. High-pressure turbine blades, plus the high-pressure and intermediate-pressure nozzle guide vanes, are super-polished, and there are other HP compressor quality improvements.
There are a few items the kits do not contain, however, such as optimized HP turbine clearances, optimized fan tip clearances or a pocket-less spinner fairing.
With another kit in the offing promising another 1% efficiency improvement, it is likely more operators will move to add the kits during a shop visit.
The Trent 700’s most high-profile airworthiness issue actually grew out of an incident involving its higher-thrust successor, the Trent 800. The January 2008 crash of a Trent 800-powered British Airways Boeing 777 was pegged to a specific combination of factors that allowed ice to form within the fuel system and collect on the front of the fuel-to-oil heat exchanger (FOHE), limiting fuel flow.
Engineers looked at in-service data from the seemingly innocuous go-around of an Airbus A330 in May 2009, which led the European airframer to conclude that the problem could exist on Trent-powered A330s and A340s as well. An airworthiness directive followed, AD 2009-0257, ordering upgraded FOHEs on Trent 700s and 500s.
Among other actions in the 700’s history, the European Aviation Safety Agency (EASA) in 2009 mandated (AD 2009-0187R2) inspections and possible replacements of front combustion liner (FCL) head sections after routine inspections detected cracked FCL heads. R-R service bulletin instructions outline acceptance criteria for any damage found.
In 2007, EASA ordered inspections of intermediate-pressure compressor rotor Stage 2-3 interstage spacers after one was found cracked on an in-service Trent 700.