47-21-10 NAVION: (Was Mandatory Note 9 of AD-782-3.) Applies to Serial Numbers NAV-4-2 Through HAV-4-1010 Which Incorporate Hartzell HC-12X20-1 Propellers.
To be accomplished not later than September 1, 1947.
The propeller control piston guide pins, Hartzell P/N A-11, require additional safetying in order to prevent loosening and subsequent loss of engine oil. This is accomplished by the installation of a 3/32-inch steel dowel through the guide pin.
(NAA Field Service Bulletin No. 30 covers this rework.)