Russell C. Buckley

Document ID: FAA-2006-24145-0018
Document Type: Public Submission
Agency: Federal Aviation Administration
Received Date: February 19 2008, at 05:08 PM Eastern Standard Time
Date Posted: February 21 2008, at 12:00 AM Eastern Standard Time
Comment Start Date: February 21 2008, at 12:00 AM Eastern Standard Time
Comment Due Date: February 19 2008, at 11:59 PM Eastern Standard Time
Tracking Number: 803b88d0
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This is comment on Rule

Airworthiness Directives; General Electric Company CF6-45 and CF6-50 Series Turbofan Engines

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Concerning the forward centerbody forward doubler installation, NAS 9307 rivet is a more reliable fastener than the specified NAS1398. The NAS9307 locking collar is designed as a positive security device that forms the rivet sleeve into the locking stem thereby promoting joint integrity while in service. NAS1398 does not offer this feature, and the lock has a tendency to release in service. At fastener seating, NAS9307 design provides a more consistent installation with visual confirmation of an acceptable mechanical fit. Previous experience with NAS1398 rivets would often result in inspection not accepting rivet installation due to misplaced locking collars. Resultant removal increased the tendency for hole oversizing. In this particular GE SB78-0244 application, there exists no tolerance for hole oversizing and subsequent larger rivet installation, see top row of rivets in attached image. First article assembly effectively utilized the NAS9307 rivet in this very tight application. Both rivets share the same tensile shear strength rating. NORDAM PRISM recommends permitting the alternate rivet usage of NAS9307 to that of the specified NAS1398.

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Russell C. Buckley

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Russell C. Buckley

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