50-38-02 BELL: (a) Applies to All Models 47B, 47B-S, 47B3, 47B3-S, 47D and 47D-S; (b) Applies to Model 47D1, Serial Numbers 145 Through 164, 174 Through 183.
Compliance required before November 15, 1950.
Service difficulties have been experienced involving fan bearing failure due to improper adjustment of the cooling fan belt. This allows the cooling fan to move forward and jam the cyclic controls. To prevent such failures, fan belt tension should be properly adjusted. In addition, a fan shaft washer should be incorporated to prevent the fan from jamming the cyclic control in case bearing failure does occur.
(Bell Service Bulletin No. 61 dated July 20, 1950, covers this subject for models under (a). Bell Service Bulletin No. 72 dated August 4, 1950, covers this subject for models under (b).)