64-17-01\tBOEING: Amdt. 766 Part 507 Federal Register July 17, 1964. Applies to Models 707 and 720 Series Aircraft. \n\n\tCompliance required as indicated. \n\n\tFailures and malfunctions occurring in the fuel dump chute limit switches of the retractable dump chute system have caused switch overheating sufficient to scorch the connecting wires. To prevent this, accomplish the following: \n\n\t(a)\tWithin 500 hours' time in service after the effective date of this AD, and thereafter at periods not to exceed 500 hours' time in service, perform a resistance check on the fuel dump chute extend limit switch, P/N's 5EN11-6B or H11-186, and on the fuel dump chute up limit switch, P/N's 2EN15-6 or H11-162. If any switch is found defective, replace before further flight. (Boeing telegraphic messages 6-7161-1-9101 and 6-7161-1-9159 sent to all operators on February 3, and March 28, 1963, respectively, cover this resistance check.) Upon compliance with paragraph (b) the provisions of this paragraph may be discontinued. \n\n\t(b)\tWithin the next 2,500 hours' time in service after August 17, 1964, replace limit switches on each fuel dump chute that do not incorporate a sealed receptacle with improved switches incorporating a sealed receptacle and replace the switch pigtail type wires with new wires and a mating sealed connector, in accordance with Boeing Service Bulletin No. 1877, or an equivalent approved by the Chief, Aircraft Engineering Division, FAA Western Region. \n\n\t(c)\tUpon request of the operator, an FAA maintenance inspector, subject to prior approval of the Chief, Aircraft Engineering Division, FAA Western Region, may adjust the repetitive inspection intervals specified in this AD to permit compliance at an established inspection period of the operator if the request contains substantiating data to justify the increase for such operator. \n\n\t(Boeing Service Bulletin 1877 dated January 23, 1964, and Boeing telegraphic messages 6- 7161-1-9101 and 6-7161-1-9159 dated February 3, and March 28, 1963, respectively, cover this subject.)\n \n\tThis directive effective August 17, 1964. \n\n\tRevised June 25, 1966.