60-11-08 SENSENICH: Amdt. 166 Part 507 Federal Register May 28, 1960. Applies to M74DM Propellers Installed On Lycoming O-320-B Series Engines Except Propellers With An "A" or "K" prefix to the Serial Number.
Compliance required within the next 100 hours of flight time or by August 1, 1960, whichever comes first, and at each periodic inspection thereafter.
As a result of three incidents of cracked hubs, the following shall be accomplished:
(a) Remove the propeller and visually inspect for cracks originating in the pilot bore. In case of doubt, any of the approved methods for aluminum alloy inspections should be used. If cracks are found, the propeller shall be retired immediately from service.
(b) If no cracks are found, polish out any scratches in the bore and break and polish any sharp edges at the front and rear chamfer of the pilot bore.
(c) When the propeller is reinstalled, torque retaining bolts to 300 inch-pounds.
(Sensenich Service Bulletin No. R-8-1 covers the same subject.)
Revised November 14, 1961.