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A full moon hung over Pratt & Whitney's test site the night its Airbus A320NEO engine ran for the first time. Whether this was a good omen or not, the company knows only a successful test effort will prove if its pivotal gamble on geared turbofan technology was correct.
Pratt began its march back into the single-aisle mainstream at 11 p.m. on Nov. 28, when the first PW1100G NEO engine fired into life on the company's West Palm Beach, Fla., test stand. “The first time we put power to the igniter it lit,” says the engine maker's Next-Generation product family Vice President Bob Saia. Since then, the engine has been taken through a 'break-in' cycle from idle to full thrust, ensuring the mechanical integrity at various power levels before clearing the PW1100G for the remainder of the forthcoming test effort.
Although it is too soon to know whether the engine is on track to meet critical fuel-burn targets, the overall performance from a temperature and speed perspective “is right on pre-test predictions,” says Saia. “We haven't yet got a true calibration in terms of fuel efficiency,” he adds. Mechanically, the engine has completed the break-in cycle testing with “no anomalies. We're really pleased with what we got.”
The initial work allows Pratt to make some design tweaks to optimize the engine at the early stages if needed. It also incorporates lessons learned from the two forerunner geared turbofan (GTF) developments, the PW1500G for Bombardier's CSeries airliner and the PW1200G for the Mitsubishi Regional Jet (MRJ). “On the PW1500G, for example, we had an unexpected rub in the last stage of the low-pressure compressor. This wasn't due to the way we broke in the engine, but because of the way it was designed,” says Saia, who adds that a quick change corrected this “subtlety.” Similarly, the initial runs also indicated that designers had allowed too much clearance in the PW1500G high-pressure compressor, which had to be tightened.