66-23-01\tBOEING: Admit. 39-288 Part 39 Federal Register September 16, 1966. Applies to Model 727 Series Airplanes Listed in Boeing Service Bulletin 28-25, Revision 1, Dated January 19, 1966. \n\n\tCompliance required as indicated, unless already accomplished. \n\n\tIt has been determined that certain of the B-nuts at the engine firewall on Boeing Model 727 Series airplanes are susceptible to cracking. To correct this condition: \n\n\t(a)\tWithin the next 600 hours' time in service after the effective date of this AD, inspect the engine fuel feed system B-nut, P/N NAS596, located at each engine firewall to determine if it is an AFCO (Aircraft Fitting, Inc.) manufactured part. Identification must be made in accordance with the instructions listed in Boeing Service Bulletin 28-25, dated December 3, 1965, or later FAA-approved revision. \n\n\t(b)\tIf the B-nut is not an AFCO part, no further action under this AD is required. If the B-nut is an AFCO part, accomplish the following before further flight: \n\n\t\t(1)\tInspect for cracks using a 10-power glass, dye penetrant or ultrasonic method. \n\n\t\t(2)\tIf cracks are found, remove the fuel line tube assembly and replace with a new part in accordance with Boeing Service Bulletin 28-25, dated December 3, 1965, or later FAA- approved revision or an equivalent approved by the Chief, Aircraft Engineering Division, FAA Western Region. \n\n\t\t(3)\tIf no cracks are found, repeat the inspection required under (1) every 600 hours' time in service until the AFCO B-nuts are replaced as specified in (c). \n\n\t(c)\tWithin the next 3,000 hours' time in service after the effective date of this AD, unless already accomplished under (b), remove all fuel feed line tube assemblies incorporating AFCO B-nuts and replace in accordance with Boeing Service Bulletin 28-25, dated December 3, 1965, or later FAA-approved revision or an equivalent approved by the Chief, Aircraft Engineering Division, FAA Western Region. \n\n\t(d)\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 period of the operator if the request contains substantiating data to justify the increase for that operator. \n\n\tThis directive effective October 16, 1966.