66-07-01\tBOEING: Amdt. 39-204 Part 39 Federal Register March 5, 1966. Applies to Models 707, 720 and 720B Series Airplanes, except Models 707-100 and 707-200 Series Airplanes With Axles Modified in Accordance With Paragraph 3, "Modification Data," of Boeing Service Bulletin 2028, or Later FAA-Approved Revision; Models 707-300, 707-400, 720, and 720B Series Airplanes with Axles Modified in Accordance With the Optional Rework Procedure of Boeing Service Bulletin No. 2221, or Later FAA-Approved Revision; Models 707-100, 707-100B, 707-200, 720 and 720B Series Airplanes with Axles Replaced in Accordance with Boeing Service Bulletin No. 2246, or Later FAA-Approved Revision; Model 707-121B; Model 707-139B; Model 707-131B; Model 707-300B Series Airplanes; Model 707-300C Series Airplanes; and Airplanes Modified to Incorporate Landing Gears With the 4 Brake Rod (Equalized Gear) Configuration. \n\n\tCompliance required as indicated. \n\n\tTo prevent further failures of the main landing gear rear axles due to hydrogen embrittlement or stress corrosion, accomplish the following:\n \n\t(a)\tWithin the next 800 hours' time in service after the effective date of this AD, unless already accomplished, and thereafter at each aft wheel brake change, accomplish the following:\n\n\t\t(1)\tVisually inspect the main landing gear aft axle for corrosion or inadequate lubrication in the region of the brake collar in accordance with paragraph 3, "Inspection Data" of Boeing Service Bulletin 1378 or later FAA-approved revision or an equivalent approved by the Aircraft Engineering Division, FAA Western Region. Remove any corrosion from the axle using the procedure described in the "NOTE" following paragraph 3.d. of Boeing Service Bulletin No. 1378 or later FAA-approved revision and grease the axle as described in paragraph 3.e. of Boeing Service Bulletin 1378 or later FAA-approved revision, before further flight. \n\n\t\t(2)\tOn Models 707-100 and -200 Series airplanes with axles reworked by chrome plating, visually inspect for cracks in the chrome plating, as described in paragraph 3, "Inspection Data" of Boeing Service Bulletin No. 1902 or later FAA-approved revision. If cracks in the chrome plating are found, remove the chrome plate, and rework any defects found in the base metal, before further flight in accordance with the "NOTE" following paragraph 3.d. of Boeing Service Bulletin No. 1902 or later FAA-approved revision applying the rework limits specified in Boeing Service Bulletin No. 1378.\n\n\t(b)\tAfter the effective date of this AD, do not chrome plate the axle, Boeing P/N's 50- 9720, 50-9720-1 and 50-9720-1S, in the area of the inner bearing for the brake collar on 707-100 and -200 Series airplanes. Axles that have been chrome plated before the effective date of this AD may be continued in service.\n \n\t(c)\tUpon request of an operator, an FAA maintenance inspector, with prior approval of the Chief, Aircraft Engineering Division, FAA Western Region, may adjust the repetitive inspection intervals required by this AD to permit compliance at an established inspection period of the operator, if the request contains substantiating data to justify the increase for that operator. \n\n\tThis directive effective April 4, 1966.\n \n\tRevised December 16, 1966.