September 11, 2012
Pratt & Whitney’s (P&W’s) first production geared turbofan engine, the PW1500G for Bombardier’s CSeries aircraft, has passed a crucial blade-out test, keeping the program on track for certification in the fourth quarter.
The milestone test comes as P&W nears completion of the first shipset of engines for Bombardier’s initial CS100 flight test aircraft at Mirabel, near Montreal. “They will be delivered to Bombardier shortly,” says P&W VP-Development Programs President Bob Saia, adding that the engine program is 90% through the certification process. First flight is expected late this year or early 2013.
The blade-out evaluation, which took place in late August, was one of the two “nail-biter” tests on the road to regulatory approval, says Saia. Two more full engines will undergo endurance runs, “and one of those at the end of 150 hours will do the triple ‘red-line’ test, which is the other nail-biter.”
In the test, one of the PW1500G’s 18 blades was deliberately detached at full power by detonating an explosive charge at its root. The test is designed to show the engine is capable of containing damage without catching fire and without failure of its mounting attachments when operated for at least 15 sec., unless the resulting damage induces a self-shutdown. “It has the highest risk because it has the highest level of unknowns, but the following blade [to the detached blade] was fully intact,” says Saia.
Although “we suffered minor damage to some of the other blades,” the remainder of the engine is in “such good condition we will use it for lightning tests.” Saia also was P&W’s VP for the Engine Alliance and oversaw certification of the GP7200 for the Airbus A380. He says that after the same test on the GP7200, which it passed, the fan rotor seized after 15 sec. and the high-pressure rotor after 3 sec. “After the PW1500G blade-off, in contrast, the engine could still be turned or ‘motored.’ I’ve never seen that done before,” he notes.
The triple red-line evaluation, which is expected to run through early October, will see another engine run for about 60 hr. at maximum fan speed, core speed and exhaust gas temperature to demonstrate its capability beyond the most extreme operating conditions. Another endurance engine, running at about the same time, will be used to verify the initial maintenance interval.
A PW1500G also is in the third and final flight-test phase on one of P&W’s Boeing 747SP flying testbeds. The program, which P&W admits began about a month later than scheduled, incorporated the latest software changes from Bombardier. It is the first to validate a fully compliant variable area nozzle and thrust reverser. Tests will “confirm the software logic and validate that for Bombardier’s flight readiness,” says Saia, who expects the flights to conclude by the end of September.
Although acknowledging “there are some sleepless nights here,” Saia says problems encountered have been “the normal optimization you’d hope to do in a situation like this.” Despite some early issues with inadequate tip clearances and endurance of some parts, all of which he says are now corrected, Saia eplains “. . . we are tickled pink with the performance. We will hit our contractual obligations on fuel burn, weight, noise and emissions on the first Bombardier engine to enter service.”
Saia says that while fuel burn on the first flight-test engine shipsets “will be under [guarantees] by 1%,” he adds planned improvements for the PW1500Gs on the fourth aircraft will bring it up to specification. The company, which base-lined a 15% fuel burn improvement for the larger CS300 variant over the CFM56- and V2500-powered Airbus A319, expects to regain some performance through efficiency improvements now under test on the sixth development engine. In addition, the engine is “better than spec” for weight after the fan blade-out tests showed the planned structural margin was not required.