Pratt & Whitney confirms that a seal problem in the engine oil system caused the uncontained failure on 29 May of the PW1500G engine powering the Bombardier CSeries FTV-1, which remains grounded until both companies validate a proposed solution with Canadian regulators.
The engine failure is still considered a “minor blip” and unrelated to the fan-drive gear system which is the unique feature of the PW1000G engine family, says Graham Webb, P&W chief engineer.
“We understand what had happened,” Webb says. “Minor modifications are in place. and we’re in process of validating all of those fixes. Once we are fully satisfied that a robust fix is in place, we’ll go off and start flying again.”
Bombardier says the CSeries CS100 test fleet will return to flight in the “coming weeks”, with the incident causing no delay in the overall schedule to deliver the first aircraft in the second half of 2015.
The incident sparked confusing reports, with Bombardier and P&W parent United Technologies officials providing conflicting accounts that the failure was traced to the oil system and the low-pressure turbine.
P&W clarifies now that the low-pressure section failed, but the cause of that failure was traced to the oil system for the overall engine, versus a separate oil system dedicated to the fan-drive gear system.
“We’ll end up changing one or two minor part numbers,” says P&W vice-president Alan Epstein. “We don’t have any plans to change any part in the [low-pressure turbine].”
The modification could be expanded to other variants of the PW1000G engine series, which also powers the Airbus A320neo, Embraer E-Jet E2, Irkut MC-21 and Mitsubishi Regional Jet.
The PW1100G engine for the A320neo is due to be certificated later this year, having completed more than 80% of its certification testing. The most challenging certification trial – the so-called triple red-line test that runs the engine at maximum speed, temperature and duration – is still pending.
The focus on the PW1500G now is getting the modifications validated and installed on about 12 engines already delivered to Bombardier, so that flight testing can resume as soon as possible.
The ongoing grounding is a public-relations problem, yet should be remembered as a footnote in the development history of the programme, P&W officials argue.
“We look at this as bad timing right before an air show,” Webb says.