EASA SIB AV-2008-05
Pratt & Whitney Canada PT6A-65 and -67 series engines - Reduction Gearbox 1st Stage Carrier Bolts Lubrication & Torque
Summary
Transport Canada Civil Aviation Service Difficulty Advisory AV-2008-05 addresses fatigue fractures in the 1st stage carrier bolts (P/N MS9490-34) of Pratt & Whitney Canada PT6A-65 and PT6A-67 series engine reduction gearboxes. The advisory highlights over twenty reported bolt failures, some causing in-flight shutdowns, primarily occurring after engine overhaul. It emphasizes the importance of proper bolt lubrication and torque during assembly to prevent stress-induced fractures.
What Changed
This advisory introduces updated maintenance practices including the use of new 1st stage carrier bolts at overhaul and strict adherence to lubrication and torque specifications as outlined in the revised Pratt & Whitney Canada engine overhaul manuals. Additionally, P&WC issued All Shop Message PT6-2008-01 to inform overhaul agencies of these critical requirements.
Why It Matters
Proper lubrication and torque of the 1st stage carrier bolts are essential to prevent fatigue fractures that can lead to engine damage, excessive vibrations, overspeed, and potentially in-flight shutdowns. Operators and maintenance organizations must follow these updated procedures to ensure engine reliability and flight safety.
What To Do
Overhaul agencies and maintenance personnel must incorporate new 1st stage carrier bolts during engine overhaul and apply the specified lubrication and torque procedures as per the updated P&WC manuals and All Shop Message PT6-2008-01. All occurrences of similar defects or failures should be reported to Transport Canada Continuing Airworthiness in compliance with CAR 591 requirements.
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