69-26-06 MCDONNELL DOUGLAS: Amendment 39-902. Supersedes Amendment 39-738, AD 69-06-03. Applies to all McDonnell Douglas Model DC-9 Series aircraft. \n\n\tCompliance required as indicated, unless already accomplished. \n\n\tTo prevent heat damage to the H.F. (if installed) and V.H.F. coaxial cables and other wiring located in the tail compartment of DC-9 Series aircraft, accomplish the following: \n\n\t(A)\tWithin the next 200 hours' time in service after the effective date of this AD, unless already accomplished, perform the following: \n\n\t\t(1)\tDetermine that the H.F. (if installed) and V.H.F. coaxial cables located in the tail compartment of the aircraft adjacent to the 8th stage bleed duct have not deteriorated due to excessive heat. The determination may be accomplished by the use of electrical tests such as fault finder pulse indications, reflectometer measurements, or X-ray inspections or a satisfactory equivalent method approved by the Chief, Aircraft Engineering Division, FAA Western Region. If the electrical tests indicate any coaxial cable impedance change in the areas of the 8th stage bleed duct or the APU exhaust shroud, or the X-ray inspections show physical change, such as noticeable drift of the center conductor, or any unsatisfactory condition in these areas, replace the damaged coaxial cables or repair the damaged areas of the cables by use of proper connectors and new coaxial sections, in conjunction with (2) and (3), below. In lieu of electrical testing of X-ray inspection an operator may replace the cables within this 200 hour period. \n\n\t\t(2)\tProvide maximum possible clearance (at least one inch) between the H.F. (if installed) and V.H.F. conduits, and the right engine 8th stage bleed duct by rotating the conduit clamps and reworking the spacers as necessary. NOTE: McDonnell Douglas DC-9 Alert Service Bulletin A23-24, dated February 21, 1969 describes this work. \n\n\t\t(3)\t(a)\tVisually inspect the APU exhaust shroud for any indications of overtemperature condition, such as shroud discoloration or exterior airframe paint discoloration around the shroud outlet. If the APU exhaust duct has been deformed or leaks, and continued use of the APU is desired, replace the duct in accordance with McDonnell Douglas S.B. 49-8, dated May 2, 1966, and Service Letters AOL-9 No. 74, dated February 6, 1967, and AOL-9 No. 139, dated September 29, 1967, or later FAA approved revisions, or an equivalent duct replacement approved by the Chief, Aircraft Engineering Division, FAA, Western Region. \n\n\t\t\t(b)\tInspect all wiring adjacent to the APU exhaust shroud for heat damage. Replace or repair to an airworthy condition all wiring found damaged. \n\n\t\t(4)\tPressure test the pneumatic duct installation in the DC-9 tail cone area in accordance with the DC-9 Maintenance Manual Temporary Revision 36-19, dated December 3, 1969, or the subsequent equivalent revision, or an equivalent pressure test approved by the Chief, Aircraft Engineering Division, FAA Western Region. \n\n\t\t(5)\tSteps (1) and (3) above, must be repeated prior to any further IFR operation after every report of a pneumatic duct malfunction or an APU exhaust duct failure until (A)(7) or (B), below, has been accomplished. \n\n\t\t(6)\tStep (4), above, must be repeated whenever pneumatic duct maintenance is performed in the tail cone area. \n\n\t\t(7)\tSteps (1) through (5), above, need not be accomplished if the operator accomplishes Step B below, within 200 hours' time in service from the effective date of this AD. \n\n\t(B)\tWithin the next 2000 hours' time in service from the effective date of this AD, unless already accomplished, perform the following in accordance with McDonnell Douglas Service Bulletin 23-24, Rev. 2, dated June 23, 1969; S.B. 23-28, dated December 3, 1969, and S.B. 27-104, Rev. 2, dated April 15, 1969, or later FAA approved revisions, or an equivalent installation and modification approved by the Chief, Aircraft Engineering Division, FAA, Western Region: \n\n\t\t(1)\tInstall an insulation blanket on the 8th stage bleed duct adjacent to the HF and VHF coaxial cable conduits. \n\n\t\t(2)\tReroute the HF (if installed) and VHF coaxial cables, and the other wiring bundle (flight recorder, interphone wiring, etc.) away from the APU exhaust shroud area where they are now located. \n\n\t\t(3)\tReplace the sections of the polyethylene dielectric type VHF and HF (if installed) coaxial cables with sections of electrically equivalent polytetrafluoroethylene (teflon) dielectric type coaxial cables from just forward of the pressure dome feed-through throughout the tail compartment, or from between just aft of the pressure dome feed-through to just aft of the exhaust duct from the air condition pack heat exchangers, and apply PF105-700 glass fiber batt and CRS-102 silicon wrap heat insulation material over all exposed low temperature cable which is not installed in conduit. NOTE: No additional rerouting or repositioning, other than that specified inparagraph (A) (2) and (B)(2), is required. \n\n\t\t(4)\tAdd a metal heat shield between the eighth stage pneumatic duct and electrical wire bundle in the tail cone R.H. side just aft of pressure panel and forward of the eighth stage bleed duct. \n\n\t\t(5)\tReposition the wire harnesses FBC and DDC, containing overheat sensor wiring and APU generator control wiring located in the tailcone L.H. side to a new position more outboard of the wing ice protection duct. \n\n\tNOTE: Compliance with the coaxial cable separation and rerouting modification also provided in AOL No. 9-333, dated August 27, 1969, and Service Bulletin No. 23-28, dated December 3, 1969, is optional. \n\n\tThis AD supersedes amendment 39-738, (34 F.R. 5427) AD 69-6-3. \n\n\tThis amendment becomes effective on December 30, 1969.