AD 99-15-09

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 737-600 series airplanes. This action requires revising the Airplane Flight Manual (AFM) to prohibit operation of the airplane under certain conditions; repetitive inspections of the tab mast fittings of the elevator tab assemblies to detect cracking; an elevator tab freeplay check; and corrective actions, if necessary. This AD also requires installing an additional fastener on the elevator tab mast fitting, which terminates the AFM revision and extends certain repetitive inspections. This AD also requires replacement of the elevator tab mast fitting with a new, improved fitting, which constitutes terminating action for the requirements of this AD. This amendment is prompted by a report of a severe vibration incident on a Boeing Model 737-800 series airplane; inspection revealed fracturing of the elevator tab mast fitting and excessive freeplay in the elevator tab. The actionsspecified in this AD are intended to prevent loss of controllability of the airplane due to excessive freeplay in the elevator tab or a free tab.

Final rule; request for comments.

99-15-09 BOEING: Amendment 39-11229. Docket 99-NM-155-AD. \n\n\tApplicability: Model 737-600 series airplanes having line numbers 1 through 190, 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 (g) 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\tToprevent loss of controllability of the airplane due to excessive freeplay in the elevator tab or a free tab, accomplish the following: \n\nAirplane Flight Manual (AFM) Revision \n\n\t(a)\tWithin 24 clock hours after the effective date of this AD, revise the Limitations Section of the FAA-approved AFM to include the following information. This may be accomplished by inserting a copy of this AD into the AFM. "Except as otherwise provided for in the AFM emergency procedures, do not operate the airplane at speeds in excess of 310 knots indicated airspeed (IAS) with speed brakes extended. Do not operate the airplane above FL 390." \n\n\t(b)\tIn the event of deployment of the speed brakes at speeds in excess of 310 knots indicated airspeed (IAS), prior to further flight after landing, accomplish the requirements of paragraph (c) of this AD. \n\nInspections and Check \n\n\tNOTE 2: Accomplishment of the inspections and check required by this AD, prior to the effective date of this AD, in accordance with Boeing Alert Service Bulletin 737-55A1068, dated June 9, 1999, is considered acceptable for compliance with the repetitive inspections and checks required by paragraphs (c) and (d) of this AD. \n\n\t(c)\tWithin 10 days after the effective date of this AD, perform a high frequency eddy current (HFEC) inspection, and a detailed visual inspection of the elevator tab mast fittings of the left and right elevator tab assemblies to detect cracking, and a one-time elevator tab freeplay check to detect freeplay of the elevator tabs, in accordance with Boeing Alert Service Bulletin 737-55A1068, Revision 1, dated June 11, 1999. \n\n\tNOTE 3: For the purposes of this AD, a detailed 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. Inspectionaids such as mirror, magnifying lenses, etc. may be used. Surface cleaning and elaborate access procedures may be required." \n\n\t\t(1)\tIf no cracking is found in any elevator tab mast fitting, repeat the HFEC and detailed visual inspections thereafter at intervals not to exceed 15 days, until accomplishment of the actions required by paragraph (d) of this AD. \n\n\t\t(2)\tIf any cracking is found in any elevator tab mast fitting, prior to further flight, accomplish the requirements of paragraph (e) of this AD. \n\n\t\t(3)\tIf any freeplay is found in any elevator tab, which is outside the limits specified in the alert service bulletin, prior to further flight, perform corrective actions in accordance with the alert service bulletin. \n\n\tNOTE 4: Boeing Alert Service Bulletin 737-55A1068, Revision 1, dated June 11, 1999, references Boeing Model 737-600/-700/-800 Maintenance Manual (AMM), Subjects 27-09-91, 27-31-00, and 51-21-99; 737 Nondestructive Test (NDT) Manual D6-37239, Part 6, Subject 55-00-00; 737 Structural Repair Manual (SRM) Subject 51-20-81; and Operations Manual Service Bulletin D6-27370-TBC ("Elevator Tab Operational Limitations"), dated June 10, 1999; as additional sources of service information to accomplish certain requirements of this AD. \n\nTime-Limited Modification \n\n\t(d)\tWithin 90 days after the effective date of this AD, install an additional high-strength fastener on the elevator tab mast fitting in accordance with Boeing Alert Service Bulletin 737-55A1068, Revision 1, dated June 11, 1999. Accomplishment of this modification constitutes terminating action for the requirements of paragraph (b) of this AD. \nFollowing accomplishment of the installation, the AFM revision required by paragraph (a) of this AD may be removed from the AFM. Following accomplishment of the installation, repeat the HFEC and detailed visual inspections required by paragraph (c) of this AD thereafter at intervals not to exceed 90 days until accomplishment of paragraph (e)of this AD. \n\nTerminating Action \n\n\t(e)\tWithin 4,000 flight cycles or 18 months after the effective date of this AD, whichever occurs earlier, replace the elevator tab mast fittings with new, improved tab mast fittings, in accordance with Boeing Service Bulletin 737-55-1063, dated July 1, 1999. Accomplishment of this replacement action constitutes terminating action for the requirements of this AD. \n\nSpares \n\n\t(f)\tAs of the effective date of this AD, no elevator tab mast fitting, part number (P/N) 183A8400-1 or 183A8400-2, shall be installed on any airplane. \n\nAlternative Methods of Compliance \n\n\t(g)\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 tothe Manager, Seattle ACO. \n\n\tNOTE 5: 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(h)\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(i)\tExcept as provided by paragraphs (a) and (b) of this AD, the actions shall be done in accordance with Boeing Alert Service Bulletin 737-55A1068, Revision 1, dated June 11, 1999, and Boeing Service Bulletin 737-55-1063, dated July 1, 1999. 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(j)\tThis amendment becomes effective on August 11, 1999.

On June 2, 1999, the FAA received a report of a severe vibration incident on a Boeing Model 737-800 series airplane, which had accumulated 3,517 total flight hours and 1,284 total flight cycles. The airplane was involved in a high-speed descent with speed brakes extended while operating at an airspeed of 320 knots. During the descent, severe vibration occurred at 250 knots. At 230 knots, the speed brakes were retracted and the vibration stopped. The landing was uneventful. \n\n\tInspection of the airplane revealed that the upper flange of the right elevator tab mast fitting, to which the elevator tab push rods are attached, was found fractured. The lower flange of the fitting was not damaged. In addition, excessive freeplay in the elevator tab also was observed and measured during the inspection. \n\n\tFurther analysis confirmed that the damage to the fitting was aggravated by speed-brake-induced airframe vibration. Such vibration could lead to damage of the elevator tab mast fitting, excessive freeplay in the tab, and consequent separation of the tab mast fitting from the tab. Excessive freeplay in the tab could result in severe airframe vibration and consequent damage to the tab, elevator, and horizontal stabilizer. Separation of the elevator tab mast fitting will result in a free tab. These conditions, if not corrected, could result in loss of controllability of the airplane. \n\n\tIn light of this information, on June 10, 1999, the FAA issued telegraphic AD T99-13-51, which is applicable to certain Boeing Model 737-700 and -800 series airplanes. In addition, the FAA has received information indicating that Boeing Model 737-600 series airplanes also are subject to the unsafe condition identified in telegraphic AD T99-13-51. Therefore, the FAA has determined that rulemaking action is necessary to address that unsafe condition on Model 737-600 series airplanes. \n\nExplanation of Relevant Service Information\n \n\tThe FAA has reviewed and approved Boeing Alert Service Bulletin 737-55A1068, Revision 1, dated June 11, 1999, which describes procedures for repetitive high frequency eddy current (HFEC) and detailed visual inspections of the tab mast fittings of the left and right elevator tab assemblies to detect cracking, and a one-time elevator tab freeplay check to detect excessive freeplay of the elevator tabs; and corrective actions, if necessary. The alert service bulletin also describes procedures for installing an additional high-strength fastener on the elevator tab mast fitting (time-limited modification). \n\n\tThe FAA also has reviewed and approved Boeing Service Bulletin 737-55-1063, dated July 1, 1999, which describes procedures for replacing a cracked elevator tab mast fitting with a new, improved fitting. Such replacement eliminates the need for repetitive inspections of the elevator tab mast fittings. \n\nExplanation of Requirements of the Rule \n\n\tSince an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design, this AD is being issued to prevent loss of controllability of the airplane due to excessive freeplay in the elevator tab or a free tab. This AD requires revising the Limitations Section of the FAA-approved Airplane Flight Manual (AFM) to prohibit operation of the airplane at certain airspeeds with the speed brakes extended, and at certain altitudes. \n\n\tThis AD also requires repetitive HFEC and detailed visual inspections of the tab mast fittings of the left and right elevator tab assemblies to detect cracking, and a one-time elevator tab freeplay check to detect excessive freeplay of the elevator tab; and corrective actions, if necessary. \n\n\tAdditionally, this AD requires installing an additional high-strength fastener on the elevator tab mast fitting (time-limited modification). Such installation terminates the AFM revision and allows extension of the repetitive interval for accomplishment of the HFEC and detailed visual inspections. \n\n\tThis AD also requires replacement of the elevator tab mast fittings with new, improved fittings, which constitutes terminating action for the requirements of this AD. \n\n\tCertain inspections and checks are required to be accomplished in accordance with Boeing Alert Service Bulletin 737-55A1068, Revision 1. Replacement actions are required to be accomplished in accordance with Boeing Service Bulletin 737-55-1063, dated July 1, 1999. \n\n\tIt should be noted that, except as otherwise provided for in the AFM emergency procedures, this AD prohibits the deployment of the spoilers at speeds in excess of 310 knots indicated airspeed (IAS) with speed brakes extended. This AD also prohibits operation of the airplane above FL 390. The FAA recognizes that under emergency circumstances, as specified in the AFM, it might become necessary to deploy spoilers in excess of 310 knots IAS. In that event, this AD requires accomplishment of the HFEC and detailed visual inspections of the elevator tab mast fittings and of the check of the tabs for freeplay, prior to further flight after landing. \n\nCost Impact \n\n\tNone of the Model 737-600 series airplanes affected by this action are on the U.S. Register. All airplanes included in the applicability of this rule currently are operated by non-U.S. operators under foreign registry; therefore, they are not directly affected by this AD action. However, the FAA considers that this rule is necessary to ensure that the unsafe condition is addressed in the event that any of these subject airplanes are imported and placed on the U.S. Register in the future. \n\n\tShould an affected airplane be imported and placed on the U.S. Register in the future: \n\n\tIt would require approximately 2 work hours to accomplish the inspection and check, at an average labor rate of $60 per work hour. Based on this figure, the cost impact of the inspection and check required by this AD would be $120 per airplane. \n\n\tIt would require approximately 3 work hours to accomplish the time-limited modification, at an average labor rate of $60 per work hour. Based on this figure, the cost impact of the time-limited modification required by this AD would be $180 per airplane. \n\n\tIt would require approximately 8 work hours to accomplish the replacement action, at an average labor rate of $60 per work hour. Required parts would cost approximately $5,149 per airplane. Based on these figures, the cost impact of the replacement required by this AD would be $5,629 per airplane. \n\nDetermination of Rule's Effective Date \n\n\tSince this AD action does not affect any airplane that is currently on the U.S. register, it has no adverse economic impact and imposes no additional burden on any person. Therefore, prior notice and public procedures hereon are unnecessary and the amendment may be made effective in less than 30 days after publication in the Federal Register. \n\nComments Invited \n\n\tAlthough this action isin the form of a final rule and was not preceded by notice and 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 99-NM-155-AD." The postcard will be date stamped and returned to the commenter. \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: