58-08-05 HAMILTON STANDARD: Applies to All 34E, 43E, and 43H Propellers Installed on TC18DA and TC18EA Series Engines.
Compliance required at first propeller overhaul after October 1, 1958, but not later than May 1, 1959.
Cases of propeller-engine overspeeds have resulted in instances of failure to feather, reversing when feathering was initiated, and in aircraft fires. In order to provide a means for limiting propeller overspeeding so that the possibility of catastrophic conditions developing will be greatly minimized, install the "RPM-Sensitive Hydraulic Pitch Lock".
(Hamilton Standard Service Bulletins Nos. 387, 472, and 472A cover this same subject.)