52-01-01 BELL: Applies to All Models 47B, 47B3, 47D Helicopters and to Model 47D1 Helicopters Serial Numbers 145 to 164, Inclusive.
Compliance required at next 300-hour overhaul, but not later than March 1, 1952.
To provide locks of increased tensile strength which will resist shearing should the blade grip adapters tend to loosen, remove the existing lockwire or blade grip adapter locks (P/N 47- 120-154-1), check the torque (3,000-3,300 inch-pounds) of the adapters and install revised locks (P/N 47-120-154-2).
(Bell Service Bulletin No. 76 covers this same subject.)