Engine — Combustion Chamber Outer Case — Inadequate Fatigue Life of Forward Flange Bolts
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AI-generated summary of the official EASA document. Verify against the PDF before acting.
What to do
Affected operators must replace the old flange bolts and modify the combustion chamber outer case and inner bypass duct at the next maintenance opportunity, but no later than 5000 engine cycles since new or since the last flange separation. For engines already incorporating the initial bolt replacement, further modifications and bolt replacements must be completed within 6000 engine cycles. The old bolts are prohibited from reinstallation as of the effective date, 2022-05-06.
Summary
Canadian Airworthiness Directive CF-2022-22 addresses the inadequate fatigue life of forward flange bolts on Pratt & Whitney Canada PW308A and PW308C engines. The directive mandates modifications to the combustion chamber outer case and inner bypass duct, along with the replacement of specific flange bolts to prevent potential bolt fractures. This AD applies to PW308A engines with build specifications BS935 and BS1249, and PW308C engines with BS1047 and BS1238.
What changed
CF-2022-22 introduces mandatory replacement of existing flange bolts P/Ns MS9698-08 and MS9698-09 with improved fatigue-resistant bolts P/Ns AS3611-5-12 and AS3611-5-13. It also requires modifications to the combustion chamber outer case and inner bypass duct to accommodate the new bolt geometry and improve bolt head clearance. The AD prohibits reinstallation of the old bolts and updates maintenance and overhaul procedures accordingly.
Why it matters
This directive is critical for aviation professionals to prevent potential low cycle fatigue cracking and fracture of flange bolts, which could lead to flange separation or engine case rupture. Compliance ensures continued engine integrity and safety, reducing the risk of in-flight engine damage. Operators, maintenance organizations, and compliance teams must incorporate these changes to meet regulatory requirements and maintain airworthiness.
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New ADs and bulletins for Pratt & Whitney Canada PW308, summarized like this page, every Monday.