64-03-01\tBOEING: Amdt. 679 Part 507 Federal Register February 4, 1964. Applies to All Models 707, 720 and 727 Series Aircraft. \n\n\tCompliance required as soon as the modification can be scheduled but not later than 1,000 hours' time in service after the effective date of this AD unless already accomplished. \n\n\tModify the fuel tank access panels and clamp rings in accordance with the following or Boeing Service Bulletin No. 1955 for 707 and 720 Series aircraft and Bulletin No. 28-7 for 727 Series aircraft or later FAA-approved revisions or an equivalent approved by the Chief, Aircraft Engineering Division, FAA Western Region: \n\n\t(a)\tRemove all fuel tank clamp rings and access doors from the aircraft. \n\n\t(b)\tRemove the phenolic insulation from the clamp ring by application of heat for 1 hour at 300 degrees F. \n\n\t(c)\tClean all mating surfaces of the access door, clamp ring, and wing skin flange of all material coating such as primer, zinc chromate and anodizing by scraping andhand sanding to base metal with 600 grit aluminum oxide paper or equivalent. \n\n\t(d)\tPrepare a mixture of conductive anticorrosive Aeroshell No. 14 grease MIL-G-25537 and Alcoa 408 aluminum powder in a ratio by weight of 35 percent of Alcoa 408 and apply to mating surfaces of clamp ring in sufficient quantity so as to obtain good surface coverage when reinstalled. \n\n\tThis directive effective February 4, 1964. \n\n\tRevised June 30, 1965.