50-46-01 DOUGLAS: Applies to All Models DC3 and C-47 Series Aircraft Which Utilize a Standpipe in the Engine Oil Tank for Propeller Feathering Oil Reserve. \n\n\tCompliance required not later than the first engine change after December 1, 1950. \n\n\tThere have been several cases of inability to feather the propeller due to inadequate feathering oil supply, following loss of engine oil. To correct this condition ascertain the quantity of oil retained in the tank by the propeller feathering standpipe with the airplane in the level flight attitude. If the quantity so retained is less than 1 1/2 gallons, rework the standpipe so that at least this quantity is retained. \n\n\tAircraft employing C-47 type oil tanks, Douglas P/N 5110511 with Douglas P/N 1355088 standpipe will be considered satisfactory.