AD 96-22-11

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 737 and 747 series airplanes, that requires replacement of Waterman hydraulic fuse assemblies with modified assemblies. This amendment is prompted by reports of failure of hydraulic system A and the standby system, due to corrosion on the magnesium piston of the hydraulic fuse and consequent failure of the fuse to close sufficiently to prevent the loss of hydraulic fluid from the system. The actions specified by this AD are intended to prevent such failure of the fuse, which could result in the failure of one or more hydraulic systems and resultant reduced controllability of the airplane.

Final rule

96-22-11 BOEING: Amendment 39-9799. Docket 96-NM-36-AD. \n\n\tApplicability: Model 737-100 and -200 series airplanes, as identified in Boeing Service Letter 737-SL-29-21, dated December 16, 1982; and Model 747-100, -200, -300, and -SP series airplanes, as identified in Boeing Service Letter 747-SL-32-19, dated January 16, 1980; 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 (d) 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 unsafecondition 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 failure of the hydraulic fuse, which could result in the failure of one or more hydraulic systems and resultant reduced controllability of the airplane, accomplish the following: \n\n\t(a)\tFor Model 737-100 and -200 series airplanes: Within 24 months after the effective date of this AD, replace Waterman hydraulic fuse assemblies, having Waterman part number (P/N) G838-8-40, G838-8-60, or G838-8-160, with modified assemblies having P/N G8381-8-40, G8381-8-60, or G8381-8-160, respectively; or with a PneuDraulics fuse specified in Boeing Service Letter 737-SL-29-21, dated December 16, 1982, including Attachments 1, 2, and 3, dated April 15, 1982. Accomplish the replacement in accordance with the service letter. \n\n\tNOTE 2: The Boeing service letter references Imperial Clevite, Inc., Service Bulletins G838- 80-4, G838-80-5, and G838-80-6, all dated April 15, 1982, as additional sources of service information for accomplishment of the replacement. \n\n\t(b)\tFor Model 747-100, -200, -300, and -SP series airplanes: Within 24 months after the effective date of this AD, replace Waterman hydraulic fuse assemblies, having Waterman P/N G905-120, with PneuDraulics assemblies having PneuDraulics P/N 6105, in accordance with Boeing Service Letter 747-SL-32-19, dated January 16, 1980. \n\n\t(c)\tAs of the effective date of this AD, no person shall install on any airplane Waterman hydraulic fuse assemblies having Waterman P/N G838-8-40, G838-8-60, G838-8-160, or G905-120. \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\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. \n\n\t(e)\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(f)\tThe replacement shall be done in accordance with the following Boeing service letters, as applicable, which include the specified list of effective pages: \n\n\nService Letter \nReferenced and Date\n\nPage Number\nRevision Level\nShown on Page\n Date \nShown on Page\n737-SL-29-21,\nDecember 16, 1982 \n1, 2\n\nAttachment 1,\t \nPage 1, 2; \nAttachment 2, \nPage 1, 2; \nAttachment 3, \nPage 1, 2 \n--\n\n--\nDecember 16, 1982 \n\nApril 15, 1982 \n747-SL-32-19,\nJanuary 16, 1980 \n1, 2\n--\nJanuary 16, 1980 \n\nThis 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 December 11, 1996.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Boeing Model 737 and 747 series airplanes was published in the Federal Register on April 30, 1996 (61 FR 18997). That action proposed to require replacement of Waterman hydraulic fuse assemblies with modified assemblies.\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 Request to Extend Compliance Time \n\n\tThe Air Transport Association (ATA) of America, on behalf of several of its members, requests that the proposed compliance time be extended from 3,000 flight hours to 24 months. The commenter indicates that accomplishment of the modification is dependent upon the ability of an outside vendor to rework the fuse assemblies and return them to the operator. The commenter states that the proposed compliance time may be insufficient for the vendor to provide this service. Additionally, two ATA members indicate that no fuse failures have occurred within their fleets. \n\n\tAnother commenter suggests that, since the compliance time would be insufficient to send the assemblies to a vendor for modification, operators of affected Model 747 series airplanes should be required to perform an initial and periodic inspections of the Waterman hydraulic fuses having part number G905-120 in accordance with the Airplane Maintenance Manual to confirm the function of the fuses until they can be replaced with PneuDraulics fuses having part number 6105. \n\n\tThe FAA concurs that the compliance time may be extended. In developing an appropriate compliance time for this AD action, the FAA considered not only the degree of urgency associated with addressing the subject unsafe condition, but the practical aspect of sending the fuse assemblies to an outside vendor for accomplishment of themodification. The FAA has considered the information presented by the commenters as to the turnaround time for accomplishment of the modification. In light of this information and the number of fuses that may need to be modified, the FAA agrees that the compliance time should be extended. The FAA has determined that extending the compliance time from the proposed 3,000 flight hours to 24 months will provide an acceptable level of safety without the need for interim inspections (as suggested by one of the commenters). Paragraphs (a) and (b) of the final rule have been revised accordingly.\n\n Request to Add a Note to the AD \n\n\tOne commenter requests that the FAA add a note to the proposal to specify that availability of replacement fuses should be considered when scheduling compliance with the AD, and to advise operators to begin accomplishing the requirements of the AD as soon as the final rule is issued. The commenter expresses concern that the lead time for obtaining replacement fuses may be inadequate and that the proposed compliance time may not be met unless operators place orders for these fuses during the early stages of the compliance period.\n \n\tThe FAA does not concur that a note should be added to the final rule. The FAA acknowledges that accomplishment of the replacement is dependent upon the ability of outside vendors to manufacture and rework rotable units within a certain time frame. However, as explained previously, the FAA has extended the compliance time for accomplishing the replacement from 3,000 flight hours to 24 months. The FAA finds that this extension should allow sufficient time for operators to obtain replacement parts within the compliance time specified in this final rule.\n\n Request to Allow Additional Method of Compliance \n\n\tOne commenter requests that the FAA revise the proposal to cite Gould/Waterman Service Bulletin G905-40-8, dated July 15, 1981, as an additional method of complying with the requirements of the AD. The Gould/Waterman service bulletin describes procedures for modifying the G905-120 Type II fuse by replacing the magnesium piston with an aluminum piston and by revising the part number to G9051-120. The commenter indicates that accomplishing the Gould/Waterman service bulletin is equivalent to replacing the fuse with a PneuDraulics fuse. \n\n\tA second commenter requests that the FAA revise the proposed rule to include replacement of Waterman fuses having part number G905-120 with Waterman fuses having part number G9051-120, in accordance with the Gould/Waterman service bulletin, as an acceptable method of compliance with the AD for Model 747 series airplanes. This commenter indicates that the change in piston subassembly materials from magnesium to an all aluminum design eliminates corrosion problems related to the G905-8-120 model fuse. The commenter adds that many operators have replaced G905-120 fuses with the replacements identified in the Gould/Waterman service bulletin. \n\n\tThe FAA does not concur that the final rule should be revised to cite the Gould/Waterman service bulletin or to specify that the G9051-120 Waterman fuse is an acceptable replacement part. The FAA has not approved the Gould/Waterman service bulletin as an additional method of complying with the AD. The FAA finds that it is inappropriate to delay the issuance of this final rule to provide time for review and approval of the Gould/Waterman service bulletin. However, should an operator of an affected Model 747 series airplane wish to accomplish the requirements of this AD by replacing Waterman fuses having part number G905-120 with Waterman fuses having part number G9051-120, that operator should submit a request for approval of such replacement, in accordance with the provisions of paragraph (d) of this final rule. \n\nRequest to Disallow Use of Certain Replacement Fuses \n\n\tOne commenter asks that the FAA disapprove any request from an operator of a Model 747 series airplane to accomplish the proposed replacement using a modified fuse in lieu of a PneuDraulics fuse having part number 6105. The commenter explains that one of the primary reasons for replacing the Waterman fuses is that the fuse would not reset once pressure was balanced in the system. The commenter indicates that the airplane manufacturer prefers to install PneuDraulics fuses having part number 6105 in the hydraulics systems of Model 747 series airplanes. The commenter adds that replacement of Waterman hydraulic fuse pistons with modified fuse pistons does not incorporate the use of the latest technology. \n\n\tThe FAA concurs partially. The FAA points out that paragraph (b) of this final rule requires that operators of Model 747 series airplanes use PneuDraulics fuse assemblies having part number 6105 as replacement parts. However, as explained previously, if an operator of these airplanes wishes to request approval of the use of other airworthy replacement parts (including modified parts) in lieu of the PneuDraulics part, the FAA would consider such a request provided that data is submitted to substantiate approval of that request.\n\n Request for Clarification of Fuse Locations and Numbers \n\n\tOne commenter requests that the FAA provide the exact position and number of fuses that require replacement. The commenter notes that the preamble of the proposed rule indicates there are eight affected fuses installed on each Model 737 series airplane. However, the commenter's records show that there are only four possible locations for the affected fuses to be installed on those airplanes. \n\n\tThe FAA concurs that clarification is necessary. A total of eight affected fuses (four wheel brake fuses, one auto brake fuse, one leading edge fuse, and two thrust reverser fuses) are installed in the standby leading edge system, the brake system, and the standby thrust reverser system of Model 737 series airplanes. Further, a total of 24 brake fuses are installed in the normal and reserve brake systems on Model 747 series airplanes. The FAA finds that no change to the final rule is necessary in response to the commenter's request. \n\nRevision to Service Letter Citation \n\n\tThe FAA has revised paragraph (a) of the final rule to indicate that Boeing Service Letter 737-SL-29-21, dated December 16, 1982, includes Attachments 1, 2, and 3, dated April 15, 1982.\n\n Revision to Cost Impact Information \n\n\tSince the issuance of the proposed rule, a vendor has advised the FAA that the cost for required replacement parts for Boeing Model 747 series airplanes will be $31,200 per airplane ($1,300 per fuse; 24 fuses per airplane). In light of this, the FAA has revised the cost impact information, below, to reflect this change.\n\n Conclusion \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 changes previously described. The FAA has determined that these changes will neither significantly increase the economic burden on any operator nor increase the scope of the AD. \nCost Impact \n\n\tThere are approximately 1,145 Boeing Model 737 series airplanes and 727 Boeing Model 747 series airplanes of the affected design in the worldwide fleet.\n\n\tThe FAA estimates that 421 Boeing Model 737 series airplanes of U.S. registry will be affected by this AD, that it will take approximately 16 work hours per airplane (8 fuses per airplane; 2 work hours per fuse) to accomplish the required actions, and that the average labor rate is $60 per work hour. Required parts that are modified by the vendor will be provided at no cost to operators. Based on these figures, the cost impact of the AD on U.S. operators of Model 737 series airplanes is estimated to be $404,160, or $960 per airplane. \n\n\tThe FAA estimates that 208 Boeing Model 747 series airplanes of U.S. registry will be affected by this AD, that it will take approximately 48 workhours per airplane (24 fuses per airplane; 2 work hours per fuse) to accomplish the required actions, and that the average labor rate is $60 per work hour. The cost for required parts will be $31,200 per airplane ($1,300 per fuse; 24 fuses per airplane). Required parts that are modified by the vendor will be provided at no cost to operators. Based on these figures, the cost impact of the AD on U.S. operators of Model 747 series airplanes is estimated to be $7,088,640, or $34,080 per airplane. \n\n\tThe cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. \n\nRegulatory 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 variouslevels 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\n List of Subjects in 14 CFR Part 39 \n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.\n\n Adoption of the AmendmentAccordingly, 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\n PART 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\t2. Section 39.13 is amended by adding the following new airworthiness directive: