70-25-03 BOEING: Boeing 747 and PRATT AND WHITNEY JT9D. Amdt. 39-1116 as amended by Amendment 39-1149. Applies to Boeing Model 747 Series Airplanes and Pratt and Whitney Aircraft Model JT9D Series Engines. \n\n\tCompliance required within the next 600 hours' time in service after the effective date of this AD, unless previously accomplished. \n\n\tTo reduce the possibility of engine surge during thrust reversal, accomplish the following: \n\n\t(a)\tModify the engine Air-Automatic Deceleration System in accordance with Pratt and Whitney Aircraft Service Bulletin Number 2841, dated August 21, 1970, or later FAA approved revision or an equivalent method approved by the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region.\n \n\t(b)\tModify the engine controls mixing box, airplane electrical wiring system, engine cowl panel, bleed duct bracket and pressure regulator vent line in accordance with the Boeing Company Service Bulletin Number 75-2002, dated September 25, 1970, or later FAA approved revision or an equivalent method approved by the Chief, Aircraft Engineering Division, FAA, Western Region. \n\n\t(c)\tUpon completion of the work described in (a) and (b) on all four engines, reverse thrust may be used to landing roll speeds as noted in the FAA approved Boeing 747 Airplane Flight Manual Normal Operating Procedures entitled RABS PROCEDURE (OPTIONAL), or an alternate procedure approved by the Chief, Aircraft Engineering Division, FAA, Western Region. \n\n\tUntil such time as the modification of all four engines on an aircraft is accomplished, install the placard described in Boeing Service Bulletin Number 78-2016, dated November 10, 1970, and referenced at Paragraph C(iv), of Boeing Service Bulletin Number 75-2002, dated September 25, 1970, or later FAA approved revisions or an equivalent placard approved by the Chief, Aircraft Engineering Division, FAA, Western Region. The placard may be removed after the modifications in (a) and (b) are accomplished. Theplacard need not be installed if RABS PROCEDURES (OPTIONAL) is not used as an optional procedure by the operator. \n\n\tAmendment 39-1116 effective January 5, 1971. \n\n\tThis amendment 39-1149 becomes effective January 29, 1971.