Airworthiness Directive · Amendment 39-18652 · Fuel
The Boeing Company Airplanes
This AD applies to The Boeing Company Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D, 747-400F, 747SR, and 747SP series airplanes, certificated in any category, as identified in Boeing Alert Service Bulletin 747-28A2306, dated October 2, 2014.
We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D, 747-400F, 747SR, and 747SP series airplanes. This AD was prompted by several reports of chafing of the wire bundles inside the electrical conduit of the forward and aft boost pumps of the numbers 1 and 4 main fuel tanks due to high vibration. These wire bundles can chafe through the wire sleeving into the insulation, exposing the wire conductors. This AD requires replacing the wire bundles inside the electrical conduit of the forward and aft boost pumps of the numbers 1 and 4 main fuel tanks with new, improved wire bundles inserted into conduit liners. This AD also requires adding a revision to the maintenance or inspection program, as applicable, to include critical design configuration control limitations (CDCCLs) for the fuel boost pump wiring. We are issuing this AD to prevent chafing of the wire bundles and subsequent arcing between the wiring and the electrical conduit creating an ignition source in the fuel tanks, which could result in a fire and consequent fuel tank explosion.
Within 60 months after the effective date of this AD: Replace the wire bundles inside the electrical conduit of the forward and aft boost pumps of the numbers 1 and 4 main fuel tanks with new, improved wire bundles inserted into conduit liners, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-28A2306, dated October 2, 2014. Accomplishing the replacement required by this paragraph terminates the inspections required by paragraphs (g), (h), and (n) of AD 2011-15-03.
Within 180 days after the effective date of this AD, revise the maintenance or inspection program, as applicable, to incorporate critical design configuration control limitation (CDCCL) Airworthiness Limitation (AWL) No. 28-AWL-24, “Fuel Boost Pump Wires In Conduit Installation—In Fuel Tank,” of Sub-section C.1, “Fuel Tank Ignition Prevention,” of Section C., “Airworthiness Limitations—Systems,” of the Boeing 747-100/200/300/SP Airworthiness Limitations (AWLs) and Certification Maintenance Requirements (CMRs) Document D6-13747-CMR, Revision June 2014; or CDCCL AWL No. 28-AWL-35, “Fuel Boost Pump Wires In Conduit Installation—In Fuel Tank,” of Sub-section B.1, “Fuel System Ignition Prevention,” of Section B, “Airworthiness Limitations (AWLs)—Systems,” of Section 9, Airworthiness Limitations (AWLs) and Certification Maintenance Requirements (CMRs), of Boeing 747-400 Maintenance Planning Data (MPD) Document D621U400-9, Revision June 2014; as applicable.
After accomplishing the revision required by paragraph (h) of this AD, no alternative actions (e.g., inspections), intervals, and/or CDCCLs may be used unless the actions, intervals, and/or CDCCLs are approved as an alternative method of compliance (AMOC) in accordance with the procedures specified in paragraph (j) of this AD.
