AD 97-26-07

On December 23, 1996, the FAA issued AD 96-26-06, amendment 39-9870 (62 FR 304, January 3, 1997), applicable to certain Boeing Model 747 series airplanes, to require a one-time inspection to detect damage of the sleeving and wire bundles of the boost pumps of the numbers 1 and 4 main fuel tanks, and of the auxiliary tank jettison pumps (if installed); replacement of any damaged sleeving with new sleeving; and repair or replacement of any damaged wires with new wires. For airplanes on which any burned wires are found, that AD also requires an inspection to detect damage of the conduit, and replacement of any damaged conduit with a serviceable conduit. That action was prompted by an FAA determination that an environment conducive to vibration exists in the conduit and wire bundles of the boost pumps and of the auxiliary tank jettison pumps, which can cause abrasion of the Teflon sleeving and consequent abrasion of the wires in the bundles. The actions required by that AD are intended to detect and correct such abrasion, which could result in electrical arcing between the wires and the aluminum conduit and consequent fire or explosion of the fuel tank.

Actions Since Issuance of Previous Rule

Since the issuance of AD 96-26-06, the FAA has received numerous reports of chafing through the outer Teflon sleeve of the wire bundles of the boost pumps of the numbers 1 and 4 main fuel tanks. Several of the sleeves had large holes. No cases of wire chafing through the insulation to the conductor were reported. Investigation revealed that two of the affected operators had varying levels of chafing with damage on 48 percent of their airplanes. Both of these operators had replaced the aluminum conduits with stainless steel conduits. Other affected operators' airplanes (with flight hour totals similar to those of the airplanes discussed previously) that were equipped with aluminum conduits had a much lower incidence of reported damage.At the time of issuance of AD 96-26-06, the FAA considered the aluminum conduit to be more susceptible to chafing and burning as a result of electrical arcing between the wires and the aluminum conduit than the stainless steel conduit. Therefore, the FAA limited the inspection required by AD 96-26-06 to Boeing Model 747 series airplanes equipped with aluminum conduits (line numbers 001 through 432 inclusive).

In light of these new findings, the FAA has determined that Boeing Model 747 series airplanes equipped with stainless steel conduits are subject to the same unsafe condition addressed in AD 96-26-06. In addition, the FAA finds that, regardless of the conduit material, repetitive inspections are necessary to determine if the sleeving of the wire bundles continues to provide a protective barrier after extended time in service.

Explanation of Relevant Service Information

Additionally, since the issuance of AD 96-26-06, the FAA has reviewed and approved Revision 1of Boeing Service Bulletin 747-28A2204, dated October 30, 1997. Revision 1 of the service bulletin revises the effectivity listing of the original version of the service bulletin (which was referenced in AD 96-26-06 as the appropriate source of service information) by adding Boeing Model 747 series airplanes having line numbers 433 through 1120 inclusive. The inspection and corrective procedures described in Revision 1 are essentially identical to those described in the original version of the alert service bulletin.

Explanation of Requirements of Rule

Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of this same type design, this AD supersedes AD 96-26-06 to require repetitive inspections, in lieu of the previously required one-time inspection, to detect damage of the sleeving and wire bundles of the boost pumps of the numbers 1 and 4 main fuel tanks, and of the auxiliary tank jettison pumps (if installed); replacement ofany damaged sleeving with new sleeving; and repair or replacement of any damaged wires with new wires. For airplanes on which any burned wires are found, this AD also continues to require an inspection to detect damage of the conduit, and replacement of any damaged conduit with a serviceable conduit. This AD also expands the applicability of the existing AD to include additional airplanes. This AD requires that operators submit a report to the FAA of any damage found as a result of the initial inspection.

Differences Between the AD and the Relevant Service Information

Operators should note that the applicability of the AD differs from the effectivity listing of Revision 1 of the referenced service bulletin. The FAA has determined that all Boeing Model 747 series airplanes are subject to the addressed unsafe condition.

Interim Action

This is considered to be interim action until final action is identified, at which time the FAA may consider further rulemaking.

Determination of Rule's Effective Date

Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days.

Comments Invited

Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 97-NM-295-AD." The postcard will be date stamped and returned to the commenter.

Regulatory Impact

The 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.

The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39 - AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. 106(g), 40113, 44701. § 39.13 (Amended) 2. Section 39.13 is amended by removing amendment 39-9870 (62 FR 304, January 3, 1997), and by adding a new airworthiness directive (AD), amendment 39-10250, to read as follows: