“We decided we’d leave it for the last test in case there was any distress. So we successfully completed the test but when we were done we had distress on the vane well beyond what was operationally acceptable. We notified Airbus that we were going to leave the test to last and there was a risk of it suffering some vane damage—but it was a conscious decision.”
In the meantime, modifications were made to engine number 3, the high-pressure system stress-test unit next in line. “We were able to make the modification before we went to test. It took us a couple of weeks to validate the root cause and identify corrective actions. It was quite simple, we just added a few cooling holes at the root of the vane.” Rather than use extra cooling air, Saia explains that the existing air is redistributed.
“We ran engine 3 at 5% above rotor red line and successfully demonstrated it.” Pratt classes the event as a success for the Block 1 phase, as it unearthed the need for a revision before it reached the final certification standard. “We go into a test not wanting to over-cool a part. You want to do enough to let it live in the environment, but nothing more,” Saia adds.
One of the earliest to begin the next phase is engine 5, the first Block 2 unit now under assembly. “It will go to test in early October but is still on its schedule,” insists Saia. The overall effort includes margin for a break between Blocks 1 and 2. “We know we are going to find areas to modify, and that certification testing will start in October and go through June 2014. We deliver engines to Airbus late in June or early July .”
From a fuel-burn perspective, Saia says the “engine is tracking on guarantee and from a weight perspective will be hundreds of pounds lighter [because of the decision early this year to drop the variable area fan nozzle feature]. We also think we’ll be lighter than our competitor, so that’s more range and less fuel for the A320NEO.”