AD 96-19-17 ACTIVE

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Boeing Model 757 series airplanes. This action requires a one-time inspection to detect discrepancies of the main battery shunt, and replacement with a serviceable part, if necessary. This action also requires inspection of certain wires, washers, and brass jam nuts to detect any discrepancy, and replacement with a serviceable part, if necessary. Additionally, this action requires inspection, and adjustment if necessary, of the torque and resistance of the installation of the main battery ground stud. This amendment is prompted by a report of interruption of electrical power during flight due to improper installation of the main battery shunt and ground stud connection of the main battery. The actions specified in this AD are intended to prevent such electrical power interruptions, which could result in loss of battery power to the source of standby power for the airplane.

Final rule; request for comments

96-19-17 BOEING: Amendment 39-9764. Docket 96-NM-223-AD. \n\n\tApplicability: Model 757 series airplanes, as listed in Boeing Alert Service Bulletin 757- 24A0079, dated August 8, 1996; certificated in any category. \n\n\tNOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (b) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it. \n\n\tCompliance: Required as indicated,unless accomplished previously.\n \n\tTo prevent interruptions of electrical power during flight, which could result in loss of battery power to the source of standby power for the airplane, accomplish the following: \n\n\t(a)\tWithin 45 days after the effective date of this AD, accomplish the actions specified in paragraphs (a)(1), (a)(2) and (a)(3) of this AD, in accordance with Boeing Alert Service Bulletin 757- 24A0079, dated August 8, 1996. \n\n\t\t(1)\tPerform an inspection of the main battery shunt, to detect any contaminated fasteners, missing pressure washers or washers having an incorrect part number, or damage to terminal posts or to the plastic base. If any discrepancy is found, prior to further flight, replace the main battery shunt, in accordance with the alert service bulletin. \n\n\t\t(2)\tPerform an inspection of the wires, washers, and brass jam nuts to detect any contamination or damage. If any discrepancy is found, prior to further flight, replace the discrepant part witha serviceable part, in accordance with the alert service bulletin. \n\n\t\t(3)\tInspect the torque and electrical resistance of the installation of the main battery ground stud, and adjust the torque and resistance of the ground stud, in accordance with the alert service bulletin. \n\n\t(b)\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\n\tNOTE 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(c)\tSpecial flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished. \n\n\t(d)\tThe actions shall be done in accordance with Boeing Alert Service Bulletin 757-24A0079, dated August 8, 1996. 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(e)\tThis amendment becomes effective on October 7, 1996.

The FAA recently has received reports indicating that interruptions of electrical power have occurred during flight, which resulted in the loss of battery power to the hot battery bus (HBB) on a Boeing Model 767 series airplane. The HBB is the source of standby power to the airplane. Investigation revealed that the reported loss of power to the HBB occurred due to cracked shunts, improper installation of fasteners on the shunt studs, and improper torque of shunt fasteners. It appears that the improper installation of fasteners on the shunt studs and improper torque of shunt fasteners occurred during manufacture. \n\n\tLoose fasteners on the shunt studs can create an open circuit or high resistance in the connection of the main battery ground stud, which can cause an interruption of the battery charger and the loss of the HBB. The loss of the HBB and associated loads will cause multiple advisory level Engine Indication and Crew Alerting System (EICAS) messages; loss of power to the standby buses/loads during standby operation; and the potential loss of center bus power. Such loss of standby power could adversely affect the function of the following systems: \n\n\t1. the captain's standby instruments, \n\t2. flight control electronics, \n\t3. Very High Frequency (VHF) communications, \n\t4. thrust reverser control, \n\t5. standby ignition, \n\t6. passenger oxygen, \n\t7. fire detection and extinguishing, and \n\t8. wing and engine anti-ice systems, among others. \n\n\tImproper installation of the main battery shunt and ground stud connection of the main battery, if not corrected, could cause an interruption of electrical power and loss of battery power to the HBB during flight. \n\n\tThe main battery shunts of the main equipment center on the Boeing Model 767 series airplanes are identical to those installed on the Boeing Model 757 series airplanes; therefore, both of these models may be subject to this same unsafe condition. The FAA has addressed this unsafe condition in Model 767 series airplanes with the issuance of AD 96-19-10, amendment 39-9757, on September 6, 1996.\n\n Explanation of Relevant Service Information \n\n\tThe FAA has reviewed and approved Boeing Alert Service Bulletin 757-24A0079, dated August 8, 1996, which describes procedures for inspection of the main battery shunt to detect contaminated fasteners, missing pressure washers or washers having an incorrect part number, or damage to the terminal posts or to the plastic base, and replacement of the main battery shunt, if necessary. The alert service bulletin also describes inspection of certain wires, washers, and brass jam nuts to detect any discrepancy, and replacement of any discrepant part with a serviceable part. Additionally, the alert service bulletin describes procedures for an inspection of the main battery ground stud to verify the torque and resistance, and adjustment of the torque and resistance, if necessary.\n \nExplanation of the Requirements of the Rule \n\n\tSince an unsafe condition has been identified that is likely to exist or develop on Boeing Model 757 series airplanes, this AD is being issued to prevent interruption of electrical power during flight, which could result in loss of battery power to the source of standby power for the airplane. This AD requires inspection of the main battery shunt to detect contaminated fasteners, missing pressure washers or washers having an incorrect part number, or damage to the terminal posts or to the plastic base, and replacement of the main battery shunt, if necessary. This AD also requires inspection of certain wires, washers, and brass jam nuts to detect any discrepancy, and replacement of any discrepant part with a serviceable part. Additionally, this AD requires an inspection of the main battery ground stud to verify the torque and electrical resistance, and adjustment of the torque and resistance, if necessary. The actions are required to be accomplished in accordance with the alert service bulletin described previously.\n\n Determination of Rule's Effective Date \n\n\tSince 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. \n\nComments Invited \n\n\tAlthough 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. \n\n\tComments 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. \n\n\tCommenters 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 96-NM-223-AD." The postcard will be date stamped and returned to the commenter.\n\n Regulatory Impact \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\tThe 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, afinal 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."\n\n List of Subjects in 14 CFR Part 39 \n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\nAdoption of the Amendment \n\n\tAccordingly, 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: \n\nPART 39 - AIRWORTHINESS DIRECTIVES \n\n\t1. The authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. 106(g), 40113, 44701. § 39.13 - (Amended) \n\n\t2. Section 39.13 is amended by adding the following new airworthiness directive:

Submit comments in triplicate to the Federal Aviation Administration (FAA),\nTransport Airplane Directorate, ANM-103, Attention: Rules Docket No. 96-NM-223-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.\n\n\tThe service information referenced in this AD may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined 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.

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