CFM International (CFMI) has completed endurance tests of an improved dual annular combustor (DAC), which it hopes will address "durability issues" experienced on the CFM56-5B/P engine, in service on the Airbus narrowbody fleets of Austrian Airlines and Swissair.

The DAC has suffered problems with cracking of the outer liner near the combustor exit and similar cracking problems with the inner liner. In addition to correcting these issues, the DAC-2C product improvement package is aimed at "reducing emissions to get closer to what we had promised", says CFM56-5 and -9 programmes manager Mike Charrier.

The shortfall was in nitrous oxide emissions, which were "within 1 EPAP[environmental limit]" of its contractural agreement says Charrier. The improvements include a modified cooling system, redesigned forward inner nozzle support and extended splashplates to improve emissions at lower power settings. Endurance cycle tests on the -2C package were completed in January and "-hardware is on its way to Evendale", in Ohio, according to Charrier. The -2C will be certificated in April and "-we will be in service with it by the third quarter", he adds.

The first engines equipped with the revised combustor will be fitted to aircraft by May. Austrian and Swissair will upgrade their entire fleets to the new configuration, says CFMI. Swissair operates 31 A319s, A320s and A321s, while Austrian flies three A321s and is just introducing the first of six A320s. Charrier adds that the recent problems of cracking in the turbine rear frame "-are behind us". New, improved, frames are now in production.

Source: Flight International