Originally Posted by tdracer
We had an incident in service a while back where a newly installed engine was squawked on the next flight for T/O thrust shortfall and excessive throttle stagger. The engine in question was a brand new spare received from the engine manufacture. It turned out that the engine manufacture used software trims in the engine test cell in order to perform some of the normal production acceptance testing on a new engine - and somehow this engine had gotten shipped with those s/w trims still installed in the FADEC . Very embarrassing for the engine company, but fortunately there was a happy outcome, and new procedures were implemented to prevent a repeat.
Sorry for the speculation, but it rather sounds like some sort of s/w trim had been installed in the engine s/w (either by the engine manufacture, or by Airbus as part of their pre-flight functional testing) and not "removed prior to flight" on the three engines.
It seems so easy to modify a software without all the tests with the test data are done. That is a specific danger of flying computers. It implies too to have a low level of written history of the system , and that bad history may hide for a long time a software mistake/fault.