AD 94-05-07 ACTIVE

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that currently requires repetitive visual inspections of wire bundles to detect damage due to chafing, and repair of damaged wires. This amendment revises the inspection and repair procedures, and provides a terminating action, which, if accomplished, will eliminate the need for the currently required inspections. This amendment is prompted by data that substantiates the need for new inspection and repair procedures. The actions specified by this AD are intended to prevent smoke and fire in the cockpit emanating from wire bundles and loss of essential cockpit instruments necessary for continued safe flight and landing of the airplane.

Final rule

94-05-07 BOEING: Amendment 39-8845. Docket 93-NM-09-AD. Supersedes AD 92-27-12, Amendment 39-8447. \n\n\tApplicability: Model 747 series airplanes, excluding Model 747-400 series airplanes; certificated in any category. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\nNOTE 1: Paragraph (a) of this AD restates the requirement for repetitive inspections contained in paragraphs (a) and (b) of AD 92-27-12. The first inspection required by this AD must be performed within the specified repetitive inspection interval after the last inspection performed in accordance with paragraphs (a) and (b) of AD 92-27-12. \n\n\tTo prevent smoke and fire in the cockpit emanating from wire bundles and loss of essential cockpit instruments necessary for continued safe flight and landing of the airplane, accomplish the following: \n\n\t(a)\tWithin 15 days after January 8, 1993 (the effective date of AD 92-27-12, amendment 39-8447): Perform a visual inspection to detect damage due to chafing of the wire bundles that extend between the P6 and P7 panels at station 400, water line 385, right buttock line 15, at Stringer 2 on the right-hand side, 6 inches aft of the P6 panel. Pay particular attention to wire bundles W418, W718, W998, and other bundles that cross over these bundles. Repeat the inspection thereafter at intervals not to exceed 120 days until the inspection required by paragraph (b) of this AD is accomplished. If any damaged wire is found, prior to further flight, repair the wire in accordance with Boeing Standard Wiring Practices Document, D6-54446. \n\n\t(b)\tWithin the next 4,000 flight hours after the effective date of this AD, accomplish the requirements of paragraphs (b)(1) and (b)(2) of this AD in accordance with Boeing Alert Service Bulletin 747-24A2186, dated January 14, 1993; or Revision 1, dated May 20, 1993. \n\n\t\t(1)\tPerform a visual inspection to detect damage due to chafing of the wire bundles above the P6 panel around station 400,water line 385, right buttock line 25 in accordance with the service bulletin. Pay particular attention to wire bundles W418, W718, W998, W1100, and W1362, and other bundles that cross over these bundles. Accomplishment of this inspection terminates the repetitive inspection requirements of paragraph (a) of this AD. If any damaged wire is found, prior to further flight, repair or replace the wire in accordance with Boeing Standard Wiring Practices Document, D6-54446. \n\n\t\t(2)\tMeasure the clearance between the wire bundles in accordance with the service bulletin. \n\n\t\t\t(i)\tIf the measured clearance between the wire bundles is 0.25 inch or greater: No further action is required by this AD. \n\n\t\t\t(ii)\tIf the measured clearance between the wire bundles is less than 0.25 inch: Repeat the inspection required by paragraph (b)(1) of this AD thereafter at intervals not to exceed 120 days. \n\n\t(c)\tInstallation of the wire modification in accordance with Boeing Alert Service Bulletin 747-24A2186, dated January 14, 1993, or Revision 1, dated May 20, 1993, terminates the repetitive inspections required by paragraphs (a) and (b) of this AD. Operators that incorporate Boeing Alert Service Bulletin 747-24A2186, Revision 1, dated May 20, 1993, shall utilize MIL-I-46852 tape wherever MIL-I-42852 tape or MIL-I-46853 tape is specified in that service bulletin. \n\n\t(d)\tAn alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO. \n\nNOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. \n\n\t(e)\tSpecial flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate the airplane to a location where the requirements of this AD can be accomplished. \n\n\t(f)\tThe inspections, measurement, and modification shall be done in accordance with Boeing Alert Service Bulletin 747-24A2186, dated January 14, 1993; or Boeing Service Bulletin 747-24A2186, Revision 1, dated May 20, 1993. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR Part 51. Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. \n\n\t(g)\tThis amendment becomes effective on April 4, 1994.

A proposal to amend part 39 of the Federal Aviation Regulations by superseding AD 92-27-12, Amendment 39-8447 (57 FR 61255, December 24, 1992), which is applicable to certain Boeing Model 747 series airplanes, was published in the Federal Register on June 3, 1993 (58 FR 31481). The action proposed to supersede AD 92-27-12 to require revised repetitive visual inspections of wire bundles to detect damage due to chafing, and repair or replacement of damaged wires; and to clarify the location of the affected wire bundles above the P6 panel. That action also would provide an optional terminating action for the repetitive visual inspections. \n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. \n\n\tOne commenter supports the proposed rule. \n\n\tThe Air Transport Association (ATA) of America, on behalf of one of its members, requests an extension of the compliance time for the proposed initial repetitive inspection of 120 days to 4,000 flight hours for Model 747-100 series airplanes, since its airplanes were not manufactured with BMS 13-51 type wire (Kapton insulated). The member points out that the description of the wire bundle failure which prompted issuance of AD 92-27-12 is typical for aromatic polyimid (Kapton insulated) type wire bundles. The member notes the similarity between that incident and the incident involving a Lockheed Model L-1011 series airplane that prompted the FAA to issue AD 84-04-01, Amendment 39-4815 (49 FR 6705, February 23, 1984). The member asserts that neither AD 92-27-12 nor this proposal compare the different failure modes and effects of aromatic polyimide (Kapton insulated) type wiring with other types of wire insulation. Finally, the member notes that the service history of Boeing Model 747-100 series airplanes indicates that there have been no reported wire bundle chafing problems in the area ofconcern. \n\n\tThe FAA does not concur on the basis of the following reasons: \n\n\tThe proposed AD addresses a potentially hazardous condition involving the manner in which certain wire bundles were installed in the affected airplanes. The type of insulation used on the wires is not directly relevant to the hazardous condition. It is the position of the FAA that the short circuit hazard will eventually occur on any Model 747-100, -200, or -300 series airplane with improperly installed wire bundles, regardless of the type of wire insulation. The intent of the proposed AD is to prevent the occurrence of a short circuit, not to alter the failure mode and/or effects of such a failure. The relevance of the type of wire insulation is limited to the amount of time required for the short circuit to occur, once chafing has begun. Types of wire utilizing harder, more abrasion resistant insulation will endure chafing for longer periods of time before occurrence of a short circuit. In this respect, Polyimide insulated wire could possibly be superior to softer types of wire insulation , such as Polytetrafluoroethylene (PTFE) insulated types of wire. \n\n\tFurther, the FAA points out that the Model L-1011 incident that prompted the issuance of AD 84-04-01 was not the direct result of the use of polyimide insulated wire. That incident was apparently due to "...mechanical damage to wire insulation due to continuing chafing..." This information was published with that AD in the Federal Register (49 FR 6705, February 23, 1984). \n\n\tAdditionally, the FAA has determined that the 120-day compliance time for the proposed initial repetitive inspection is justified when an additional hazard is considered, which was not present in the Model L-1011 incident. The Model L-1011 incident resulted in a smoke and fire hazard, due to an electrical fault of a window heat wire bundle. The loss of the window heat function will not, in itself, result in an immediate safety of flight hazard.In the case of the Model 747 incident that prompted issuance of AD 92-27-12, the electrical fault resulted in the loss of numerous essential cockpit instruments necessary for continued safe flight and landing, in addition to the smoke and fire hazard. \n\n\tFinally, the FAA disagrees that service experience should be used to justify a reduction of the frequency of the repetitive inspection intervals for Model 747-100 series airplanes. While the FAA does not dispute the commenter's claim regarding lack of in-service chafing incidents on the Model 747-100, the FAA points out that the wire bundles above the P6 panel are installed on all Model 747-100, -200, and -300 series airplanes in accordance with the same type design data. As a result, the FAA cannot establish that the wire bundle installation on Model 747-100 series airplanes has specific design features that preclude these airplanes from the potential hazardous condition. The FAA does recognize, however, that some of the airplanes affected by the proposed AD may not exhibit the wire bundle chafing problem. For this reason, paragraph (b)(2)(i) of the proposed AD provides for termination of the repetitive inspections on airplanes that successfully pass a wire bundle clearance inspection and measurement procedure. \n\n\tATA, on behalf of one of its members, requests that proposed paragraph (c) only cite the original issue of Boeing Service Bulletin 747-24A2186, dated January 14, 1993, since Revision 1, dated May 20, 1993, contains several typographical errors. The FAA partially concurs. The FAA clarifies that Revision 1 erroneously refers to military specification MIL-I-42852 and MIL-I-46853 insulating tapes in several paragraphs. MIL-I-46852 tape is the correct military specification number and should be inserted wherever MIL-I-42852 or MIL-I-46853 is identified. The FAA points out that Revision 1 of the service bulletin contains descriptive information not found in the original release of the service bulletin, which may assist operators in performing the optional wire bundle modification. The FAA has included a statement in paragraph (c) of this AD to clarify that MIL-I-46852 tape shall be utilized wherever MIL-I-42852 tape or MIL-I-46853 tape is specified, for those operators that incorporate Revision 1 of the service bulletin. Therefore, with this information included in the AD, the FAA considers that the service bulletin references are appropriate in paragraph (c) of this AD. \n\n\tAfter careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the change previously described. The FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD. \n\n\tThere are approximately 700 Model 747 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 184 airplanes of U.S. registry will be affected by this AD, that it will take approximately 1.5 work hours per airplane to accomplish the required actions, and that the average labor rate is $55 per work hour. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $15,180, or $83 per airplane. This total cost figure assumes that no operator has yet accomplished the requirements of this AD. \n\n\tShould an operator elect to accomplish the optional terminating action that would be provided by this AD action, the number of work hours required to accomplish it would be approximately 1 per airplane, and the cost of required parts would be approximately $32 per airplane. \n\n\tThe regulations adopted herein will not have substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. \n\n\tFor the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES." \n\nList of Subjects in 14 CFR Part 39 \n\nAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\nAdoption of the Amendment \n\nAccordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 14 CFR part 39 of the Federal Aviation Regulations as follows: \n\nPART 39 - AIRWORTHINESS DIRECTIVES \n\t1.\tThe authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89. \n\n§ 39.13 - (Amended) \n\t2.\tSection 39.13 is amended by removing amendment 39-8447 (57 FR 61255, December 24, 1992), and by adding a new airworthiness directive (AD), amendment 39-8845, to read as follows:

The service information referenced in this AD may be obtained from Boeing\nCommercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the Federal Aviation Administration (FAA), Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Stephen Oshiro, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206) 227-2793; fax (206) 227-1181.