51-28-02 FRANKLIN: Applies to Model 6V4-178 Series Engines Prior to Serial Number 17690 and 6V4- 200 Series Engines Prior to Serial Number 26235.
Compliance required as indicated.
To preclude the possibility of oil pump failure, oil pump gears (P/N 10673 and 17736) must be inspected at each 300 hours of operation. Excessively galled gears must be replaced. If same part numbers are used for replacements, the 300-hour inspections will still apply. If carbonitrided oil pump drive gear, P/N 19377, and oil pump driven gear, P/N 19373, are installed, no further inspection is required. When these new carbonitrided gears are installed, suffix "P" must be stamped after the serial number of the engine on the nameplate - example: No. 1700P.
(Franklin Service Bulletin No. 86, revised November 1, 1951, covers this same subject.)
This supersedes AD's 51-22-02 and 51-11-03.