Summary
We propose to adopt a new airworthiness directive (AD) for the products listed above. This proposed AD results from mandatory continuing airworthiness information (MCAI) issued by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as:
A PW617F-E engine powered twin engined aircraft had recently experienced an uncommanded power reduction on one of its engines. Investigation showed that the Fuel Filter Bypass Valve poppet in the Fuel Oil Heat Exchanger (FOHE) on that engine had worn through the housing seat, allowing unfiltered fuel and debris to contaminate the Fuel Metering Unit (FMU), resulting in fuel flow drop and subsequent power reduction. Pratt & Whitney Canada Corp. has confirmed that this is a dormant failure that could result in an unsafe condition. The PW615F-A engine Fuel Filter Bypass Valve is very similar to that of PW617F-E, but so far there have been no operational abnormalities reported due to subject valve failure on PW615F-A engines. However, evaluation by Pratt & Whitney Canada Corp. has confirmed similar dormant failure of worn through poppets of the subject valve on some 615F-A engine installations, which could affect both engines at the same time on an aircraft and may result in an unsafe condition.
We are proposing this AD to prevent uncommanded power reduction, which could result in the inability to continue safe flight and safe landing.