52-21-01 BELL: Applies to Model 47 Helicopters as Noted Below.
Compliance required by October 15, 1952.
To prevent engine mount shifting on the rubber Lord mounts, the following applicable Lord mount guards must be installed:
1. 178 H. P. Engines - Models 47B, 47B3, and 47D Helicopters. If not already incorporated, install two 47-612-123-1 guards on engine mount. When properly installed, a 5/32 inch torque offset exists between engine mount clamp and rubber Lord mount. This offset is at the rearward side of right hand Lord mount and the forward side of left hand Lord mount.
2. 200 H. P. Engines - All Model 47 Helicopters. Inspect the two 47-612-123-3 guards to be sure they have 7/32 inch ears. If no guards are installed or the ears are less than 3/16 inch they must be replaced with the new type guards. When properly installed, a 1/4 inch torque offset exists between engine mount clamp and rubber Lord mount. This offset is at the rearward side of right hand Lord mount and the forward side of left hand Lord mount.
(Bell Service Bulletin No. 79, Revision A, dated July 7, 1952, covers this same subject.)
This supersedes AD 52-01-04.