May 7, 2015: The CFM LEAP-1B has entered flight testing on GE’s company-owned Boeing 747. The engine is for the Boeing 737 MAX. Aviation Week has a story and one section in particular caught our eye, as it relates to the controversy over the test results of fuel consumption.
“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.”
Aspire Aviation reported last month that the LEAP-1B was coming up 4%-5% short, a huge number that Boeing immediately denied; CFM declined comment at the time. Airline Economics later reported the same figure. Our information from our sources was conflicting: we were told by one that the shortfall was 2%, a figure we had been hearing for some time and which was characterized as not unusual at this stage; and one other that reported the 4%-5% figure. There it sat. We did a “what-if” analysis of the effect on the MAX at the 2% and 4% numbers.
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%.