AD 99-26-21

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Boeing Model 737-300, -400, -500, -600, -700, and -800 series airplanes. This action requires a one-time detailed visual inspection of certain wire bundles and hydraulic hoses for the electric motor driven pump (EMDP) for hydraulic system "B" located in the right main wheel well to detect discrepancies; and corrective actions, if necessary. This amendment is prompted by a report that the wire bundle to the EMDP had been chafed by the pressure hose for hydraulic system "B" on a Model 737-700 series airplane, and reports of failed or damaged case drain or pressure hoses on the EMDP for hydraulic system "B" on Model 737-400 series airplanes. The actions specified in this AD are intended to prevent electrical arcing due to chafing between certain hydraulic hoses and adjacent wire bundles, which could result in a consequent increased risk of fire.

Final rule; request for comments

99-26-21 BOEING: Amendment 39-11480. Docket 99-NM-342-AD.\n\tApplicability: Model 737-300, -400, and -500 series airplanes, as listed in Boeing Alert Service Bulletin 737-29A1076, Revision 1, dated October 21, 1999; and Model 737-600, -700, and -800 series airplanes, as listed in Boeing Alert Service Bulletin 737-29A1077, Revision 1, dated October 21, 1999; certificated in any category. \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 (e) 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\tCompliance: Required as indicated, unless accomplished previously. \n\tTo prevent electrical arcing due to chafing between certain hydraulic hoses and adjacent wire bundles, which could result in a consequent increased risk of fire; accomplish the following:\nActions for Model 737-300, -400, and -500 Series Airplanes\n\t(a)\tFor certain Model 737-300, -400, and -500 series airplanes on which the actions specified by Boeing Alert Service Bulletin 737-29A1076, dated April 2, 1998, have not been accomplished: Within 90 days after the effective date of this AD, perform a one-time detailed visual inspection of wire bundle W0334 and the hydraulic case drain and pressure hoses for the electric motor driven pump (EMDP) for hydraulic system "B" to detect any discrepancy (e.g., damage or chafing of wire bundle W0334 and the hydraulic case drain and pressure hoses, and incorrect separation between those components), in accordance with Part 1 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-29A1076, Revision 1, dated October 21, 1999.\n\t\t(1)\tIf no discrepancy is found, no further action is required by this paragraph.\n\t\t(2)\tIf any discrepancy is found, prior to further flight, perform corrective actions in accordance with Part 1 of the Accomplishment Instructions of the alert service bulletin. \n\tNOTE 2: For the purposes of this AD, a detailed visual inspection is defined as: "An intensive examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at an intensity deemed appropriate by the inspector. Inspection aids such as mirrors, magnifying lenses, etc. may be used. Surface cleaning and elaborate access procedures may be required."\n\t(b)\tFor certain Model 737-300, -400, and-500 series airplanes on which the actions specified by Boeing Alert Service Bulletin 737-29A1076, dated April 2, 1998, have been accomplished: Within 90 days after the effective date of this AD, perform a one-time detailed visual inspection of wire bundle W0334 and the hydraulic case drain and pressure hoses for the EMDP for hydraulic system "B" to detect any discrepancy (e.g., damage or chafing of wire bundle W0334 and the hydraulic case drain and pressure hoses; and incorrect separation between those components), in accordance with Part 2 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-29A1076, Revision 1, dated October 21, 1999.\n\t\t(1)\tIf no discrepancy is found, no further action is required by this paragraph.\n\t\t(2)\tIf any discrepancy is found, prior to further flight, perform corrective actions in accordance with Part 2 of the Accomplishment Instructions of the alert service bulletin. \nActions for Model 737-600, -700, and -800 Series Airplanes \n\t(c)\tFor certain Model 737-600, -700, and -800 series airplanes on which the actions specified by Boeing Alert Service Bulletin 737-29A1077, dated March 4, 1999, have not been accomplished: Within 90 days after the effective date of this AD, perform a one-time detailed visual inspection of wire bundle W5230 and the hydraulic case drain and pressure hoses for the EMDP for hydraulic system "B" to detect any discrepancy (e.g., damage or chafing of the W5230 wire bundle and the hydraulic case drain and pressure hoses; and incorrect separation between those components) in accordance with Part 1 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-29A1077, Revision 1, dated October 21, 1999.\n\t\t(1)\tIf no discrepancy is found, no further action is required by this paragraph.\n\t\t(2)\tIf any discrepancy is found, prior to further flight, perform corrective actions in accordance with Part 1 of the Accomplishment Instructions of the alert service bulletin.\n\t(d)\tFor certain Model 737-600, -700, and -800 series airplanes on which the actions specified by Boeing Alert Service Bulletin 737-29A1077, dated March 4, 1999, have been accomplished: Within 90 days after the effective date of this AD, perform a one-time detailed visual inspection of wire bundle W5230 and the case drain and pressure hoses for the EMDP for hydraulic system "B" to detect any discrepancy (e.g., damage or chafing of the W5230 wire bundles and the hydraulic case drain and pressure hoses; and incorrect separation between those components), in accordance with Part 2 of Boeing Alert Service Bulletin 737-29A1077, Revision 1, dated October 21, 1999.\n\t\t(1)\tIf no discrepancy is found, no further action is required by this paragraph.\n\t\t(2)\tIf any discrepancy is found, prior to further flight, perform corrective actions in accordance with Part 2 of the Accomplishment Instructions of the alert service bulletin. \nAlternative Methods of Compliance\n\t(e)\tAn alternative method of compliance or adjustment ofthe 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\tNOTE 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.\nSpecial Flight Permits\n\t(f)\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. \nIncorporation by Reference\n\t(g)\tThe inspection and corrective actions shall be done in accordance with Boeing Alert Service Bulletin 737-29A1076, Revision 1, dated October 21, 1999; or Boeing Alert Service Bulletin 737-29A1077, Revision 1, dated October 21, 1999; as applicable. 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\t(h)\tThis amendment becomes effective on January 31, 2000.

The FAA has received one report from an operator of a Boeing Model 737-700 series airplane describing how one of the three electrical wires in the wire bundle to the electric motor driven pump (EMDP) had chafed the pressure hose for hydraulic system "B." The FAA also has received several reports of failed or damaged case drain or pressure hoses on the EMDP for hydraulic system "B" for Boeing Model 737-300, -400, and -500 series airplanes. Chafing between the hydraulic case drain and pressure hoses could damage the hoses, and cause a hydraulic leak and failure of the pressure hose. Chafing between the wire bundle and hydraulic hoses could damage those components, and lead to electrical arcing between the components and a consequent hydraulic leak, which could result in an increased risk of fire. \nExplanation of Relevant Service Information\n\tThe FAA has reviewed and approved Boeing Alert Service Bulletin 737-29A1076, Revision 1 (for Model 737-300, -400, and -500 series airplanes), and Boeing Alert Service Bulletin 737-29A1077, Revision 1 (for Model 737-600, -700, and -800 series airplanes); both dated October 21, 1999; which describe procedures for an inspection of wire bundles W0334 and W5230, and the hydraulic case drain and pressure hoses for the EMDP for hydraulic system "B" to detect any discrepancies; and corrective actions, if necessary. Corrective actions include repair of the wire bundles if any damage is found; replacement of any hose that is damaged outside specified limits, and any incorrectly sized or loose components; and certain modifications. Modifications include adjusting or changing certain support clamps, fittings, and check valves; and installing additional clamps and spacers in the hydraulic hoses to obtain specified separation between the wire bundle and the hoses. For certain EMDP's, modifications also include ensuring that certain components are attached correctly.\nThe alert service bulletins also specify a test of the EMDP if wire bundles W0334 or W5230 were repaired, or a leak test if the hydraulic case drain or pressure hoses were replaced in accordance with either Part 1 or Part 2 of the Accomplishment Instructions of the Boeing alert service bulletins, as applicable. \nExplanation of Requirements of the Rule\n\tSince an unsafe condition has been identified that is likely to exist or develop on other Boeing Model 737-300, -400, -500, -600, -700, and -800 series airplanes of the same type design, this AD is being issued to prevent electrical arcing due to chafing between certain hydraulic hoses and adjacent wire bundles, which could result in a consequent increased risk of fire. This AD requires a one-time detailed visual inspection of wire bundles W0334 and W5230 and the hydraulic case drain and pressure hoses for the EMDP for hydraulic system "B" located in the right main wheel well to detect discrepancies; and corrective actions, if necessary. The actions are required to be accomplished in accordance with the alert service bulletins described previously, except as described below.\nDifferences Between This AD and the Alert Service Bulletins\n\tOperators should note that the alert service bulletins recommend accomplishment of the inspection and corrective actions as soon as manpower and equipment are available. However, the FAA has determined that the compliance time proposed by the manufacturer would not address the identified unsafe condition in a timely manner. In developing an appropriate compliance time for this AD, the FAA considered not only the manufacturer's recommendation, but the degree of urgency associated with addressing the subject unsafe condition, the average utilization of the affected fleet, and the time necessary to perform the inspection (less than two hours). In light of all these factors, the FAA finds a 90-day compliance time for accomplishing the required actions to be warranted, in that it represents an appropriate interval of timeallowable for affected airplanes to continue to operate without compromising safety. \nDetermination of Rule's Effective Date\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. \nComments Invited\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 rulemay 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\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\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 99-NM-342-AD." The postcard will be date stamped and returned to the commenter.\nRegulatory Impact\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\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,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."\nList of Subjects in 14 CFR Part 39\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.\nAdoption of the Amendment\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:\nPART 39 - AIRWORTHINESS DIRECTIVES\n\t1. The authority citation for part 39 continues to read as follows: \nAuthority: 49 U.S.C. 106(g), 40113, 44701. \n§ 39.13 (Amended)\n\t2. Section 39.13 is amended by adding the following new airworthiness directive: