AD 99-19-27

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 737-100, -200, -300, -400, and -500 series airplanes, that requires a one-time inspection of the main landing gear (MLG) wheel assemblies to determine whether certain parts are installed, and follow-on corrective actions, if necessary. For certain airplanes, this amendment also requires eventual modification of MLG wheel assemblies, which terminates the requirements of this AD. This amendment is prompted by incidents of multiple tie bolt failures on certain BFGoodrich wheel assemblies. The actions specified by this AD are intended to prevent failure of multiple tie bolts of MLG wheel assemblies, which could result in failure of the wheel rim, rapid release of tire pressure, and possible consequent damage to the airplane and injury to passengers and flightcrew.

Final rule

99-19-27 BOEING: Amendment 39-11314. Docket 98-NM-251-AD.\n\n\tApplicability: Model 737-100, -200, -300, -400, and -500 series airplanes, 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 (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\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo preventfailure of multiple tie bolts of main landing gear (MLG) wheel assemblies, which could result in failure of the wheel rim, rapid release of tire pressure, and possible consequent damage to the airplane and injury to passengers and flightcrew, accomplish the following: \n\n\t(a)\tWithin 60 days after the effective date of this AD, perform an inspection of the MLG wheel assemblies or perform other verifications (such as a records review) to determine the part number (P/N) of each assembly. If no wheel assembly manufactured by BFGoodrich Aerospace and having P/N 3-1398-1, 3-1439-2, or 3-1439-3 is installed on the airplane, no further action is required by this AD. \n\n\t(b)\tExcept as provided by paragraph (d) of this AD, if any MLG wheel assembly manufactured by BFGoodrich Aerospace and having P/N 3-1398-1, 3-1439-2, or 3-1439-3 is installed on the airplane, within 60 days after the effective date of this AD, accomplish the actions specified by paragraph (b)(1) or (b)(2) of this AD. \n\n\t\t(1)\tAccomplish the actions specified by (b)(1)(i) or (b)(1)(ii) of this AD. \n\t\t\t(i)\tReplace all tie bolts, nuts, and washers of the MLG wheel assembly with parts having the same P/N's, in accordance with the BFGoodrich component maintenance manual. Thereafter, repeat the replacement of tie bolts, nuts, and washers, at intervals not to exceed 5 tire changes, until the actions specified by paragraph (b)(2) or paragraph (c) of this AD have been accomplished. Or \n\n\t\t\t(ii)\tPerform a detailed visual inspection to detect fractures of any of the 16 tie bolts on each MLG wheel assembly, in accordance with the Boeing 737 airplane maintenance manual. Thereafter, repeat the inspection at intervals not to exceed 100 flight cycles until the actions specified by paragraph (b)(2) or paragraph (c) of this AD have been accomplished. If any fracture of any tie bolt is found during any inspection performed in accordance with this requirement, prior to further flight, replace the tie bolt, nut, and washer, in accordance with the BFGoodrich component maintenance manual, with new parts having the same P/N's. \n\n\tNOTE 2: For the purposes of this AD, a detailed visual inspection is defined as: "An intensive visual 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 intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc. may be used. Surface cleaning and elaborate access procedures may be required." \n\n\t\t(2)\tRevise the FAA-approved maintenance program as specified in paragraph (b)(2)(i) or (b)(2)(ii) of this AD. \n\n\t\t\t(i)\tRevise the FAA-approved maintenance program to require replacement of all tie bolts, nuts, and washers of the MLG wheel assembly with parts having the same P/N's, in accordance with the BFGoodrich component maintenance manual, at intervals not to exceed 5 tire changes. Or \n\n\t\t\t(ii)\tRevise the FAA-approved maintenance program to require a detailed visual inspection to detect fractures of any of the 16 tie bolts on each MLG wheel assembly, in accordance with the Boeing 737 airplane maintenance manual, at intervals not to exceed 100 flight cycles. If any fracture of any tie bolt is found during any inspection performed in accordance with this requirement, prior to further flight, replace the tie bolt, nut, and washer, in accordance with the BFGoodrich component maintenance manual, with new parts having the same P/N's. \n\n\tNOTE 3: After the maintenance program has been revised to include the procedures specified in paragraph (b)(2)(i) or (b)(2)(ii) of this AD, operators are not required to subsequently record AD compliance each time the replacement or inspection is performed. \n\n\t(c)\tIf any MLG wheel assembly manufactured by BFGoodrich Aerospace and having P/N 3-1398-1, 3-1439-2, or 3-1439-3 is installed on the airplane: Except as provided by paragraph (d) of this AD, within 2 years after the effective date of this AD, modify any BFGoodrich Aerospace wheel assembly, having P/N 3-1398-1, 3-1439-2, or 3-1439-3; by replacing all existing tie bolts, nuts, and washers, with new, improved parts; and by converting the P/N of the MLG wheel assembly to 3-1398-2 (for BFGoodrich wheel assemblies having the old P/N 3-1398-1), 3-1439-5 (for BFGoodrich wheel assemblies having the old P/N 3-1439-2), or 3-1439-6 (for BFGoodrich wheel assemblies having the old P/N 3-1439-3), as applicable; in accordance with BFGoodrich Aerospace Service Bulletin 3-1439-32-13, or BFGoodrich Aerospace Service Bulletin 3-1398-32-16, both dated August 20, 1993, as applicable. Such modification constitutes terminating action for the requirements of this AD, and the FAA-approved maintenance program procedures specified by paragraph (b)(2) of this AD may be removed following accomplishment of the requirements of this paragraph. \n\n\t(d)\tAirplanes on which the modification required by paragraph (c) of this AD is accomplished within the compliance time specified in paragraph (b) of this AD are not required to accomplish the actions required by paragraph (b). \n\nAlternative Methods of Compliance \n\n\t(e)\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 4: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. \n\nSpecial Flight Permits \n\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. \n\nIncorporation by Reference \n\n\t(g)\tThe modification shall be done in accordance with BFGoodrich Aerospace Service Bulletin 3-1439-32-13, dated August 20, 1993; or BFGoodrich Aerospace Service Bulletin 3-1398-32-16, dated August 20, 1993, 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 BFGoodrich Aerospace, Aircraft Wheels and Brakes, P.O. Box 340, Troy, Ohio 45373. 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(h)\tThis amendment becomes effective on October 20, 1999.

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 all Boeing Model 737-100, -200, -300, -400, and -500 series airplanes was published in the Federal Register on November 18, 1998 (63 FR 64013). That action proposed to require a one-time inspection of the main landing gear (MLG) wheel assemblies to determine whether certain parts are installed, and follow-on corrective actions, if necessary. For certain airplanes, that action also proposed to require eventual modification of MLG wheel assemblies, which would terminate the requirements of this AD. \n\nComments \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\nSupport for the Proposal \n\n\tOne commenter has no objection to the proposed AD. \n\nExplanation of Change Made to Proposal \n\n\tThe FAAhas clarified the inspection requirement contained in the proposed AD. Whereas the proposed specified a visual inspection, the FAA has revised paragraphs (b)(2)(i) and (b)(2)(ii) of this final rule to clarify that its intent is to require a detailed visual inspection. Additionally, Note 2 has been added to the final rule to define that inspection. \n\nRequest to Revise Applicability \n\n\tOne commenter requests that the applicability of the proposed AD be revised to read, "All Model 737-100, -200, -300, -400, and -500 series airplanes certificated in any category, having wheel assemblies manufactured by BFGoodrich installed." In support of its request, the commenter states that the current applicability does not exclude airplanes that do not have BFGoodrich wheel and brake assemblies installed. \n\n\tThe FAA does not concur. The purpose of the AD is to assure that all operators verify part numbers, determine if BFGoodrich wheel assemblies are installed, and if so, take appropriate action. No change to the applicability section of the AD is made in this regard. However, the FAA recognizes that a records review can verify part numbers, and as discussed below, paragraph (a) of the AD has been revised to essentially accomplish the result sought by the commenter. \n\nRequest to Revise Inspection Procedures \n\n\tSeveral commenters request that the proposed inspection procedures of the main landing gear (MLG) wheel assemblies be revised to allow for a records review in lieu of a visual inspection to determine whether certain parts are installed. In support of this request, the commenters noted that other wheel assemblies (AlliedSignal) are not interchangeable with BFGoodrich wheel assemblies, and since it is not necessary to determine the type of wheel assemblies that are installed, a review of records would be less expensive than a visual inspection. \n\n\tThe FAA concurs with the commenters' request to revise the inspection procedures required by paragraph (a) of this AD. The FAA recognizes that a visual inspection is not necessary to determine the type of wheel assemblies that are installed. In light of this, the FAA has revised paragraph (a) of this final rule to require, "an inspection of the MLG wheel assemblies or perform other verifications (such as a records review) to determine the part number (P/N) of each assembly." \n\nRequest for Clarification of Discussion Section \n\n\tOne commenter requests that the FAA clarify the description in the Discussion Section of the proposed AD of the tie bolt failures to indicate that they occurred only on certain BFGoodrich wheel assemblies that are installed on the main landing gear (MLG) of Boeing Model 737-300 and -400 series airplanes. \n\n\tThe FAA agrees that the Discussion section of the proposed rule may have been unclear regarding the incidents of tie bolt failures on certain BFGoodrich wheel assemblies. The FAA acknowledges that no reports of failures have been reported for Boeing Model 737-100, -200, or -500 series airplanes. However, because the Discussion section is not restated in the final rule, no change to this final rule is necessary in this regard. \n\nRequest for Revision of Cost Impact Information \n\n\tOne commenter requests that the cost impact information of the proposed AD be revised to clarify the usage of parts should an operator elect to accomplish the replacement. The commenter requests adding a phrase to clarify that if the same part number steel tie bolt fasteners were used, such replacement will require no additional work hours if accomplished during a regularly scheduled tire change. \n\n\tThe FAA concurs with the commenter's request. The cost impact information, below, has been revised accordingly. \n\n\tThe same commenter requests that the cost impact information of the proposed AD be revised to clarify the types of parts to be used. The commenter requests adding a phrase to clarify that the modification of the wheel assembly be accomplished by installing improved, Inconel tie bolt fasteners, and that it would require no additional work hours per airplane if the modification is accomplished during a regularly scheduled tire change. \n\n\tThe FAA concurs with the commenter's request. The cost impact information, below, has been revised accordingly. \n\nRequest for Clarification of Requirements \n\n\tOne commenter requests that the proposed rule be revised to clarify certain requirements. The commenter suggests that additional information be provided to clarify the visual inspections, replacements, and terminating action. \n\n\tThe FAA does not concur. The FAA acknowledges the comment, however, the commenter did not make any specific recommendations. Therefore, no change to the final rule in this regard is necessary. \n\nConclusion \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 increase the economic burden on any operator nor increase the scope of the AD. \n\nCost Impact \n\n\tThere are approximately 460 Model 737-100, -200, -300, -400, and -500 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 118 airplanes of U.S. registry will be affected by this AD. \n\n\tIt will take approximately 1 work hour per airplane to accomplish the required one-time inspection, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the one-time inspection required by this AD on U.S. operators is estimated to be $7,080, or $60 per airplane. \n\n\tThe cost impact figure discussed above is 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\n\tShould an operator elect to accomplish the repetitive visual inspection, it would take approximately 1 work hour per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the repetitive inspections, if accomplished, is estimated to be $60 per airplane, per inspection cycle. \n\n\tShould an operator elect to accomplish the replacement using the same part number steel tie bolt fasteners, such replacement would require no additional work hours if accomplished during a regularly scheduled tire change. Required parts would cost $2,840 per airplane ($710 per wheel). Based on these figures, the cost impact of the replacement, if accomplished, is estimated to be $2,840 per airplane, per replacement cycle. \n\n\tShould an operator elect to accomplish the revisions to the FAA-approved maintenance program, it would take approximately 1 work hour per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the maintenance programrevision, if accomplished, is estimated to be $60 per airplane. \n\n\tShould an operator be required to accomplish the necessary modification of the wheel assembly by installing improved Inconel tie bolt fasteners, it would require no additional work hours per airplane, if the modification is accomplished during a regularly scheduled tire change. Required parts would cost $4,848 per airplane ($1,212 per wheel). Based on these figures, the cost impact of any necessary modification is estimated to be $4,848 per airplane. \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 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.For 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\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\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: