50-06-01 BELL: Applies to All Model 47D1 Helicopters.
Compliance required not later than March 31, 1950.
Ventral fin installation, Bell P/N 47-267-058 should be replaced by the revised ventral fin and fixed tab installation, Bell P/N 47-267-063. The new installation is designed to eliminate the possibility of those fatigue failures which have been experienced in the old design.
Upon completion of the above modifications, the inspections required by AD 49-34-02 may be discontinued.
(Bell Service Bulletin No. 71 covers the same subject.)