Squawk Box

July 2001 Issue

Blind Mischief

Blind rivets are popular for sheet metal repairs, but may not hold

The following information is derived from the FAA’s Service Difficulty Reports and Aviation Maintenance Alerts.

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While examining the wreckage of a Eurocopter BK-117, metallurgists traced the cause of the accident to fatigue cracking in multiple components of the vertical fin structure, including the skin and spar.

The cracking of the skin originated at some rivet holes and grew undetected to a length of approximately 5˝ inches. Without support from the skin, the adjacent spar cracked until it essentially became severed. Eventually the vertical fin failed in flight. The fatigue crack propagation in the skin was concealed by the installation of the yaw SAS servo mount supp...

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