AD 59-20-04

59-20-04 BOEING: Applies to the following 707-100 series aircraft only: Serial Numbers 17586 through 17591, 17609 through 17612, 17628 through 17652, 17658 through 17672, 17696 through 17702, 17925 through 17927. Compliance required not later than November 15, 1959. There have been failures of the welded flanges located at each end of the turbocompressor bleed duct mounted on the high pressure bleed port of the engine. These failures have caused damage to the surrounding structure due to excessive pressure and temperature in the cowl and also required engine shutdown due to high EGT and low EPR. Therefore, the following modification(s) shall be accomplished as indicated: (a) An additional filetweld shall be added to the external side of the three flanges on the turbocompressor engine bleed duct assembly. (Each pod utilizing a turbocompressor.) (b) The existing boss weld on the turbocompressor engine bleed duct shall be strengthened by welding gussets to both the boss and duct. These gussets are to be fabricated in accordance with Boeing Service Bulletin No. 543 figure 2. NOTE: The above modification(s) are included in Boeing Airplane Company Service Bulletin No. 543 dated August 14, 1959.