Document ID: chunk:federal_register_of_legislation:F2006B06220:body:0:p3
Version: federal_register_of_legislation:F2006B06220
Segment Type: other
Provision Reference: 
Character Range: 5733–6963

accordance with Hartzell SB 165 E is carried out at intervals not exceeding 400 hours or 36 calendar months, whichever occurs first. Any removed hub shall be permanently retired from service.

           Background:  There have been incidents of hub cracks in Hartzell three blade "compact" aluminium hub propellers. Cracks have originated in the threads of a grease fitting hole on the side of the hub and have also originated in the fillet radius area. The cracks are believed to be observable with careful visual examination using a 10X magnifying glass.

           As the cracks propagate around the blade arm of the hub their progression accelerates and results in failure of one hub half which can then, potentially, progress to blade separation. Replacement with the later style hubs, post 83, provides terminating action for this Directive. The previous amendment reduces the repetitive inspection interval while this amendment, in line with the manufacturer's SB, further reduces the inspection intervals, introduces an eddy current or fluorescent penetrant inspection requirement, allows chamfer modifications of the hub and for specific aircraft types mandates replacement of pre 83 hubs within a certain time frame.