Good news for CFM (and by extension, Boeing and Comac):

http://leehamnews.com/2015/05/07/cfm-leap-1b-enters-flight-testing/

“When we build development engines they are heavily instrumented and built to accomplish extreme test conditions and durability,” he explains. “They are intentionally deteriorated and have open clearances because they are built for the ‘corner point’ in the test effort. We do pre-test predictions and we are within 0.5% of every one, so we are right on track. We fully expect to be right on our commitment as we enter into service.”

Last week, we received a clarifying explanation that appears to track with the Aviation Week article and the excerpt above. We were told that the 4%-5% number came from a test stand test in which the tolerances of the engine were much looser than the optimal performance engine. The clearances, we were told, were not to specification–and the result was the 4%-5%.