47-41-04 BELL: (Was Mandatory Note 16 of AD-1H-2.) Applies to Models 47B and 47B3 Helicopters.
Compliance required not later than next 50-hour transmission teardown inspection after December 1, 1947.
To improve attachment of the inner race bearing on the bottom of the main rotor mast and to prevent possible chipping, the lower mast plug should incorporate a bolted retaining washer.
(Bell Service Bulletin 47C41 dated June 26, 1947, covers the detail installation.)