2008 06 19
Service history reveals four events of uncontained impeller failures involving the JT15D-1 series engine. All of these failure events resulted in penetration of the aircraft fuselage.
Investigation has determined the root cause to be surface irregularities on the rear face of the impeller; in the form of a machining groove or step that resulted in a crack initiation that propagated to fracture.
In response, Pratt & Whitney Canada (P&WC) revised the engine overhaul manual, part number (P/N) 3017543, to Revision 14, recommending a more detailed inspection of the impeller.
A recent engine overhaul inspection revealed a crack at the rear face of the impeller, which, if left undetected, could have resulted in impeller fracture and the liberation of high-energy fragments.
P&WC issued service bulletin (SB) 7590 on 23 May 2003, recommending a borescope inspection and provided acceptance criteria in accordance with overhaul manual, Revision 14, or later approved revision. SB 7590 is only applicable to impeller P/N 3020365, and recommends that impellers be inspected during the next shop visit or within the next 250 cycles for engines that have impellers with a TCSN (total cycles since new) equal to or greater than 5000 cycles, whichever occurs first.
Transport Canada Civil Aviation (TCCA) previously issued airworthiness directive (AD) CF-2003-17 that mandated compliance with SB 7590. Shortly thereafter the Federal Aviation Administration (FAA) issued a corresponding AD 2004-04-09. These respective ADs are applicable to JT15D-1/-1A/-1B series engines with impeller P/N 3020365. Impellers with rear-face conditions that do not meet the SB 7590 criteria are to be repaired or replaced before further operation.
At this time, P&WC is aware that only 123 confirmed borescope impeller inspections having been carried out. Consequently, P&WC has issued service information letter (SIL) JT15D-042 dated 6 November 2007, to remind operators that SB 7590 requires feedback to P&WC on the engines that have been inspected, even if the condition is found satisfactory.
TCCA reminds all Canadian operators, maintainers and/or overhaul agencies that they must comply with AD CF-2003-17 in accordance with CAR 593. TCCA strongly recommends that foreign operator, maintainers and/or overhaul agencies comply with the mandatory SB 7590, annotate compliance in the engine logbook, and ensure that P&WC is informed accordingly.
Similar defects or further occurrences of this nature, or malfunctions, defects and failures occurring on any aeronautical product should be reported to Transport Canada, Continuing Airworthiness, in accordance with CAR 591, mandatory Service Difficulty Reporting requirements.
For further information, contact a Transport Canada Centre, or Mr. Barry Caldwell at 613-952-4358 or e-mail firstname.lastname@example.org
For Director, National Aircraft CertificationRobin Lau
Note: For the electronic version of this document, please consult the following Web address:www.tc.gc.ca/eng/civilaviation/certification/menu.htm