57-06-04 WRIGHT: Applies to All Aircraft Incorporating C18CA, C18CB, TC18DA, and TC18EA Series Engines.
Compliance required as indicated.
Results of recent investigations indicate that the engine front section bearing durability can be improved by accomplishing the following:
1. At next engine overhaul the engine front section must be assembled with the propeller shaft thrust bearing (ball bearing) behind the radial bearing (roller bearing) as viewed from the propeller end of the engine.
(Wright Aeronautical Division Service Bulletins Nos. C18C-252, TC18D-255, and TC-18E-66 cover this same subject.)
Propellers must be balanced in accordance with instructions contained in applicable propeller manufacturer's recommendations.
2. Engines overhauled after April 15, 1957, must incorporate engine propeller shaft thrust bearings (ball bearings) and radial bearings (roller bearings) that have been inspected for proper internal bearing clearances in accordance with instructions issued by the Wright Aeronautical Division in their Service Letter dated March 22, 1957.