CFM is planning to move the first core for Leap X testing into a test cell at its Evandale, Ohio facility on 15 May in preparation to start the first set of tests in June.

The core comprises a single-stage high-pressure turbine (HPT), an eight-stage compressor and a combustor. CFM plans to capture about 2,200 parameters of data through a 100h test effort lasting one to two months.

Leap X is a turbofan in development by CFM partners GE and Snecma to power next-generation narrowbodies, which promises a 16% improvement in fuel burn over the best-performing CFM56.

Noting that the single-stage turbine is one of the highest loaded in existence, Leap X programme manager Ron Klapproth says the core will be run at compressor ratios of roughly 20:1 "to find out where the stall line is".

The planned compressor ratio for the Leap X single-stage HPT is 16:1. A two-stage HPT scheduled to begin testing in mid-2011 could take those ratios to 22:1 or 23:1, but CFM cautions it needs to collect data from both sets of tests before making a final decision on turbine architecture.

CFM executive vice-president Chaker Chahrour says the manufacturer's decision on a single- or two-stage turbine will be a function of the testing of the current core and "core 2".

Klapproth says CFM aims to freeze the design of core 2 by year-end to support testing in 2011. Testing that starts in June will largely entail monitoring the performance of the compressor, turbine efficiency and the twin annular pre-mixing swirler (TAPS) II based on GEnx technology.

CFM plans to run a full engine demonstrator in 2012 ahead of a 2016 certification target, although Chahrour says that without some clarity from the aircraft manufacturers, "there is no need to certify an engine if there's not an application for it".

He says CFM is not writing off the open rotor because it wants to hedge its bets, but has found during talks with a few airlines about the technology that they are not that enamoured with the concept. The carriers are anxious to achieve the 16% improvement in fuel burn over the best-performing CFM56 promised by Leap X "as soon as possible".

Source: Flight International