55-25-01 BELL: Applies to Model 47G Helicopters Below Serial Number 1450 Which Have Hydraulic Boost System Installed.
Compliance required as soon as practical but not later than January 15, 1956.
The manufacturer advises that the lateral cyclic bellcrank, P/N 47-725-073-1 attachment bolt P/N AN 174-34 is too short, positioning the threaded area in the forward lateral bellcrank support bracket hole, which may result in the threads flattening out and elongating the support bracket bolt hole.
It is therefore requested that the bolt holes in the bellcrank support bracket be inspected for elongation and the bolt replaced with a longer bolt. If the bolt holes are found elongated beyond permissible tolerance (maximum hole diameter of 0.2520 inch) doubler plates must be added. Redrill and line ream new holes. Replace the AN 174-34 bolt with a new longer bolt P/N AN 174-35, unless doubler plates are added, in which case install AN 174-36 bolts.
(Bell's Mandatory Service Bulletin No. 104, dated November 11, 1955, covers this same subject.)