Airbus is redistributing A320neo certification work among its three flight-test articles to recoup time lost on the first aircraft, which has not flown since the company found a defect in one of its two Pratt & Whitney PW1100G-JM geared-turbofan (GTF) engines in April. The manufacturer has revised some testing dates and modified the A320neo flying program to accommodate the changes.

A three-month “pause” in testing of the initial two aircraft, both GTF-powered, followed discovery of a manufacturing defect in a 10-inch-diameter retaining ring in the powerplant’s combustor section, but Airbus still expects to begin deliveries by year-end. The second GTF-powered A320neo resumed testing on July 27.

The third machine—equipped with alternative CFM International Leap-1A engines—has continued flying, pausing briefly only for engine-upgrade installation, on-board equipment enhancement and maintenance. Plans now call for it to undertake additional work previously earmarked for the GTF-powered A320neos and unrelated to engine systems.

Airbus told AIN that details of “individual aircraft test allocation is an area which we simply can’t comment on,” but that flexibility “was something we had facilitated into the test program from the outset.” Nevertheless, it points out that all flight-test campaigns dedicate many certification tests to the airframe and that after calibration work related to aerodynamics and specific engine-performance and -thrust parameters finish, crews can perform  airframe-related tests involving such items as handling qualities on a test machine “with either engine type.” In addition, other work—for example, fuel-, hydraulic-, and navigation-systems testing—can “sometimes be performed independently of the engine installed.”

Key tests completed during the first phase of the test campaign—before April’s pause in flying—confirmed that A320Neo performance met all requirements, according to Airbus. Work remaining involves mainly certification tests, including those relating to hot-weather, high-altitude and automatic-landing operations. "We have also adapted the remaining flight-test schedule to take into account these revised dates and ensure priority to the tests remaining to achieve the certification,” Airbus told AIN.

By July 29, the A320neo flight-test fleet had logged more than 570 flight hours during more than 180 flights. “Despite flight-test interruptions, the delivery stream is expected to begin in 2015,” concluded Airbus.