Pratt & Whitney identified the source of the failure of one of the PW1500Gs on the first Bombardier CSeries flight-test aircraft as a “seal issue” in the oil system, not the low-pressure turbine as previously indicated by Bombardier. However, in a press briefing in London on July 13 it declined to specify the precise origin of the oil leak or offer detailed information about the expected timing of its fix.
PW1000G programs vice president Graham Webb asserted that Pratt engineers have gained a good understanding of what caused the uncontained failure on May 29 in Mirabel, Canada, and noted that that they have already put in place adjustments and “minor modifications,” validation of which continues at Pratt facilities in Connecticut.
“Once we and Bombardier…are fully satisfied that we have a robust fix in place we’ll start flying again with the agreement of the regulators,” said Webb. “We look at this as kind of bad timing…right before an air show to have an event like this. Nonetheless, this is part of the process.”
Characterizing the event as “a minor speed bump” on the PW1500’s path toward entry into service, “a plumbing issue,” and part of the normal development process, Webb suggested that every engine manufacturer experiences comparable problems before it introduces a new product.
Still, Pratt & Whitney executives resisted any temptation to precisely identify what engineers believe caused the uncontained failure. “The area that was affected was in the back end of the engine, but that’s all we are saying,” said Pratt & Whitney Commercial Engines president David Brantner. “I don’t want to speculate about anything else…the issue is a seal problem in the oil system.”
Notwithstanding his insistence that Pratt fully understands the issue, Webb explained that Pratt resists offering further detail because it hasn’t fully validated the fix and that it doesn’t want to risk releasing erroneous information. Both he and Brantner said Bombardier mistakenly identified the low-pressure turbine as the source of the problem because it disseminated information that proved premature. “Bombardier is talking about what it thinks it is; there was early information and somebody said ‘Gee, it could be in the LPT,’” said Brantner. “We’re telling you right now, rear compartment, oil, seal issue, plumbing. That’s what we’re fixing.”