46-39-04 DOUGLAS: (Was Mandatory Note 7 of AD-762-7.) Applies to C-54 Series Aircraft. \n\n\tTo be accomplished not later than November 15, 1946. \n\n\tInstances of valve freezing, due to ice forming in the detent chamber, have been reported on fuel tank selector and crossfeed valves. To prevent valve freezing, the Parker and Hydro Aire valves must be reworked by filling the detent chamber with Dow Corning compound No. 4 and installing a washer to retain the compound and to act as a water shield. \n\n\t(Douglas Drawings 4331597 and 2331524 cover this same subject.)