48-18-04 LOCKHEED: Applies to Model 49-46 Aircraft Serial Numbers 1975 Through 1980 and 2021 Through 2088.
Compliance with the following was required prior to September 19, 1947, by direct notification of operators.
Add thermocouple to cabin supercharger bevel gear housing, and direct reading indicator in cockpit to record temperatures of the rear supercharger universal coupling support bearing.
(LAC Service Bulletin 49/SB-390 covers this same subject.)