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58-07-01 HARTZELL: Applies to All HC-12X20, HC-13X20, HC-82X and HC-83X Series Propellers.
Compliance required at the next propeller overhaul.
To minimize the possibility of fatigue failure of the split rings used to retain the blades in the hub, replace all unmarked split rings with new split rings marked with the letter "N". The new production rings have a higher safety factor. Recent failures involving the old type split rings have been covered in airworthiness directives concerned with the particular propeller model or hub-blade combination involved.
(Hartzell Service Bulletin No. 58 covers this same subject.)
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