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.

Testing now is focused on measuring the effectiveness of the engine's secondary flow system to adequately cool and seal the turbine, and other hotter running stages, as well as the various cavities. “So this first engine is involved in a lot of first-of-model testing, and evaluations of the fundamental architecture. So if we uncover anything, we will have time to adapt the design,” Saia says.

The second and third engines are in assembly with the second expected to start tests around mid-February. This will be used for operability and performance trials, as well as fan work that will include crosswind testing to check the ability of the inlet and compressor to handle various simulated angles of attack. For “fan-mapping” tests, the engine will be fitted with flapper valves to form a rudimentary variable area fan nozzle to alter the pressure ratio. “We also want to characterize the structural element of the fan for operability as well as for stress or flutter,” Saia adds. The same engine will be flown in the second quarter of 2013 on Pratt's Boeing 747SP flying testbed with a production-representative variable nozzle.

The third and fourth test engines will be heavily instrumented “stress-test” units aimed at gathering strain-gauge measurements of the high- and low-pressure spools, respectively. The sheer amount of internal wiring required for these measurements means the stress-test engines enter the build cycle much earlier, says Saia. Here again, Pratt hopes to take advantage of work already performed on the PW1500G. “We have completed all of the certification testing on things like aerofoil stress (on PW1500G), so before the PW1100G starts testing we've already got the fundamentals of it characterized. There may be differences in the lengths of the blades and such, but it takes a lot of risk out of the early engines. That is not to say we still may not break a motor now and then.”

Engine certification is targeted for August 2014, providing adequate margin before the first flight of the Pratt-powered A320NEO, which is planned for early in the fourth quarter that year. In all, eight PW1100Gs will be involved in the test program, which is divided into two main blocks. The first block involves the engine now under test as well as three sister units. Performance and operability characterization, sea level tests and evaluation of systems will be conducted on these. Block 2 engines will undergo evaluations required for simultaneous FAA and EASA (European Aviation Safety Agency) certification such fan blade out, bird ingestion and cyclic endurance. Entry-into-service of the first PW1100G-equipped A320NEO is scheduled for October 2015.

A virtually identical version of the PW1100G is also in development for the Irkut MS-21, which is due to enter service in 2017. Pratt completed the critical design review of the PW1400G variant with the Russian manufacturer in November, says Saia. The key differences to the NEO engine involve the “arrangement of the external packaging,” adds Saia, referring to the positioning of the accessory gearbox and hook-ups for power and aircraft systems extraction.

Pratt and Irkut are also working with Bombardier-owned Shorts of Belfast, Northern Ireland, on development of the nacelle. “We are in the last stages of finalizing the nacelle architecture, and will be testing it in early 2014,” Saia says. The nacelle deal, which was announced in June 2012, was a breakthrough for Shorts, which had seen its market share in nacelle work gradually eroded in recent years by competition from the U.S. and France. Although it currently produces complete nacelles for the General Electric CF34 and Rolls-Royce BR710, as well as components for Rolls's Trent 700 and International Aero Engines' V2500, the MS-21 is the company's first significant work for a next-generation airliner.

Until the MS-21, all the nacelles for Pratt's GTF series were produced by Goodrich, a company now known as United Technologies Aerospace Systems since becoming part of Pratt & Whitney's parent company earlier this year. Safran's Aircelle is providing the nacelle for the CFM Leap-1A, which competes with the PW1100G on the A320NEO, as well as for the Leap-1C-powered C919 in development by Comac of China.

Pratt and Irkut also signed a definitive agreement earlier this year to confirm the PW1400 as the only Western engine option on the MC-21. The agreement came 2.5 years after Irkut chose Pratt's geared turbofan for its new family of 150-210-passenger aircraft. Irkut plans to complete design work on the MC-21 by year-end and to make the first flight in 2016. The indigenous Aviadvigatel PD-14A turbofan will be the alternate powerplant.

Despite the fact it will already be running the identically configured NEO core engine, Pratt will begin development of the PW1400G with a dedicated test unit for Irkut, says Saia. However, the company plans to convert two NEO Block 1 test engines into MS-21-configured Block 2 standard for certification of the engine for the Russian airliner.

Meanwhile, development testing continues of the PW1200G for the delayed MRJ. “We have completed all Block 1 testing and finalized the Block 2 design,” says Saia. More than 1,600 hr. of testing have been accomplished, and the first Block 2 engines will be assembled in the second quarter. Certification testing is due to begin by mid-year with Federal Aviation Regulations Part 33 approval expected late in the fourth quarter “or early 2014,” Saia adds. Engine development has slid to the right to stay in line with the aircraft schedule, which Mitsubishi announced in April has been delayed by more than a year to 2015. However, Pratt says this is deliberate. “We like the engine to be close to the aircraft schedule so if anything changes on the aircraft, like accessories, we can use the last certification tests to qualify to the required standard,” Saia adds.