AD 96-25-18

This amendment adopts a new airworthiness directive (AD), applicable to all Boeing Model 767 series airplanes, that requires inspections of the components of the leading edge outboard slat; replacement of the control rod end, if necessary; and various follow-on actions. This amendment is prompted by reports of skewed panels of the outboard leading edge slat due to failure of a corroded rotary actuator or the control rod. The actions specified by this AD are intended to prevent such conditions, which could result in reduced controllability of the airplane and damage to or cracking of the leading edge slats or the fixed leading edge of the wing.

Final rule

96-25-18 BOEING: Amendment 39-9861. Docket 95-NM-244-AD. \n\n\tApplicability: All Model 767 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 otherwise 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 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 reduced controllability of the airplane and damage to or cracking of the leading edge slats or the fixed leading edge of the wing, accomplish the following: \n\n\tNOTE 2: Actions specified in this AD that were accomplished prior to the effective date of this AD in accordance with Boeing Alert Service Bulletin 767-27A0137, dated May 18, 1995, are considered acceptable for compliance. \n\n\t(a)\tPrior to the accumulation of 10,500 total hours time-in-service, or within 500 hours time-in-service after the effective date of this AD, whichever occurs later: Perform a visual inspection to verify proper clearance of the overtravel stop of the outboard leading edge slats 2, 3, 4, 5, 8, 9, 10, and 11, in accordance with Part I of Boeing Service Bulletin 767-27A0137, Revision 1, dated November 30, 1995, or Chapter 27-81-20 of the Boeing 767 Airplane Maintenance Manual (AMM). \n\n\tNOTE 3: Although the Boeing service bulletin indicates that the actions required by this paragraph may be accomplished in accordance with the "operator's equivalent procedure," this AD does not permit use of an "operator's equivalent procedure" unless it has been approved as an alternative method of compliance in accordance with paragraph (d) of this AD. \n\n\t\t(1)\tIf proper clearance exists, repeat the inspection for proper clearance thereafter at intervals not to exceed 6,000 hours time-in-service or 18 months, whichever occurs later. \n\n\t\t(2)\tIf clearance exists, but is incorrect, at the next convenient maintenance interval, but no later than 500 flight hours after accomplishment of the inspection, adjust the stop clearance for the slats in accordance with the service bulletin or AMM. Repeat the inspection for proper clearance thereafter at intervals not to exceed 6,000 hours time-in-service or 18 months, whichever occurs later. \n\n\t\t(3)\tIf no clearance exists (i.e., stop contact), prior to further flight, adjust the stop clearance for the slats in accordance with the service bulletin or AMM. After the adjustment, within 3,000 hours time-in-service or 1,500 flight cycles after accomplishing the inspection required by paragraph (a) of this AD, whichever occurs later, replace the rotary actuator and adjacent offset gearbox in accordance with the service bulletin or AMM. After replacement, repeat the inspection for proper clearance at intervals not to exceed 6,000 hours time-in-service or 18 months, whichever occurs later. \n\n\t(b)\tPrior to the accumulation of 10,500 total hours time-in-service, or within 500 hours time-in-service after the effective date of this AD: Perform a visual inspection to detect external signs of internal corrosion of the rotary actuator of the outboard leading edge slats 2, 3, 4, 5, 8, 9, 10, and 11, in accordance with Part II of the Boeing Service Bulletin 767-27A0137, Revision 1, dated November 30, 1995, or Chapter 27-81-20 of the Boeing 767 AMM. \n\n\tNOTE 4: Although the Boeing service bulletin indicates that the actions required by this paragraph may be accomplished in accordance with the "operator's equivalent procedure," this AD does not permit use of an "operator's equivalent procedure" unless it has been approved as an alternative method of compliance in accordance with paragraph (d) of this AD.\n\n\t\t(1)\tIf no sign of internal corrosion is detected, accomplish paragraph (b)(1)(i) or (b)(1)(ii) of this AD, as applicable. \n\n\t\t\t(i)\tFor airplanes on which a rotary actuator having part number (P/N) 256T2120-3 or earlier is installed: Within 4,000 flight hours after the effective date of this AD, replace that rotary actuator with a serviceable rotary actuator having P/N 256T2120-5 or later, in accordance with the service bulletin or AMM. After replacement, repeat the inspection of the rotary actuator at intervals not to exceed 6,000 flight hours or 18 months, whichever occurs later. \n\n\t\t\t(ii)\tFor airplanes on which a rotary actuator having P/N 256T2120-5 or later is installed: Repeat the inspection of the rotary actuator thereafter at intervals not to exceed 6,000 flight hours or 18 months, whichever occurs later. \n\n\t\t(2)\tIf any sign of internal corrosion is detected, accomplish paragraph (b)(2)(i) or (b)(2)(ii) of this AD, as applicable. \n\n\t\t\t(i)\tFor airplanes on which a rotary actuator having part number (P/N) 256T2120-3 or earlier is installed: Within 4,000 flight hours after the effective date of this AD, replace that rotary actuator with a serviceable rotary actuator having P/N 256T2120-5 or later, in accordance with the service bulletin or AMM. After replacement, repeat the inspection of the rotary actuator at intervals not to exceed 6,000 flight hours or 18 months, whichever occurs later.\n\n\t\t\t(ii)\tFor airplanes on which a rotary actuator having P/N 256T2120-5 or later is installed: Within 6,000 flight hours or 18 months after accomplishing the initial inspection required by paragraph (b) of this AD, replace that rotary actuator with a serviceable rotary actuator having P/N 256T2120-5 or later, in accordance with the service bulletin or AMM. After replacement, repeat the inspection required of the rotary actuator at intervals not to exceed 6,000 flight hours or 18 months, whichever occurs later. \n\n\t(c)\tPrior to the accumulation of 10,500 total hours time-in-service, or within 500 hours time-in-service after the effective date of this AD: Perform a visual inspection to verify proper installation (including loose bolts and missing lockwires) of the control rods of the outboard leading edge slats 2, 3, 4, 5, 8, 9, 10, and 11, in accordance with Part III of the Boeing Service Bulletin 767- 27A0137, Revision 1, dated November 30, 1995; or Chapter 27-81-20 of the Boeing 767 AMM. \n\n\tNOTE 5: Although the Boeing service bulletin indicates that the actions required by this paragraph may be accomplished in accordance with the "operator's equivalent procedure," this AD does not permit use of an "operator's equivalent procedure" unless it has been approved as an alternative method of compliance in accordance with paragraph (d) of this AD. \n\n\t\t(1)\tIf all control rods are installed properly, repeat the inspection to verify proper installation thereafter at intervals not to exceed 6,000 flight hours or 18 months, whichever occurs later.\n \n\t\t(2)\tIf any bolt is loose or any lockwire missing, prior to further flight, tighten the bolt or install a new lockwire, in accordance with the service bulletin or the AMM. Repeat the inspection to verify proper installation thereafter at intervals not to exceed 6,000 flight hours or 18 months, whichever occurs later. \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 6: 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 inspections and replacements shall be done in accordance with Boeing Service Bulletin 767-27A0137, Revision 1, dated November 30, 1995. 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(g)\tThis amendment becomes effective on January 31, 1997.

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 767 series airplanes was published in the Federal Register on December 13, 1995 (60 FR 63992). That action proposed to require inspections of the components of the leading edge outboard slat; replacement of the control rod end, if necessary; and various follow-on actions. \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\tTwo commenters support the proposed rule. \n\nRequest to Revise the Description of the Addressed Unsafe Condition \n\n\tOne commenter notes that the description of the cause of the addressed unsafe condition that appeared in the Summary and Discussion sections of the preamble to the notice states that ". . . the cause of the skewed panels is attributed to either corrosion of the rotary actuator, cracking of the control rod, or incorrect clearance of the overtravel stop . . . ." The commenter suggests that a more accurate description of the cause would be ". . . failure of a corroded rotary actuator, due to excessive loads caused by the incorrect clearance of the overtravel stop, or failure of the control rod." \n\n\tThe FAA concurs and has revised the appropriate sections of this preamble to specify this language. \n\nRequests to Extend the Compliance Time for Inspections Performed Previously \n\n\tSeveral commenters request that the compliance time for paragraphs (a), (b), and (c) of the proposal be revised to allow credit for visual inspections performed previously within 6,000 hours time-in-service, or 18 months, whichever occurs later. One commenter submitted an identical request, but for inspections performed previously within 5,500 hours time-in-service. Two other commenters narrowed this request to apply to only paragraph (b) of the proposal. These commenters state that, as the NPRM is currently worded, it penalizes operators who promptly started accomplishing Boeing Service Bulletin 767-27A0137 after its issuance on May 18, 1995. These commenters assert that their suggested compliance times will coincide with the repetitive inspection requirements of the proposal. \n\n\tThe FAA concurs with the commenters' request to allow credit for all inspections accomplished prior to the effective date of this AD. The FAA has re-reviewed the recommended compliance time in the subject service bulletin and the proposed AD. The FAA does not intend that operators be penalized for accomplishing the actions specified in Boeing Service Bulletin 767- 27A0137 in an expeditious manner. Although the service bulletin recommends that credit be allowed only for inspections accomplished previously within 3,000 hours time-in-service, the FAA finds that no data exist to warrant limiting credit for such inspections to 3,000 hours. Therefore, the FAA has removed the phrase "unless previously accomplished within the last 3,000 hours time- in-service prior to the effective date of this AD" from paragraphs (a), (b), and (c) of the final rule. In the case of this AD, if the initial inspection has been accomplished prior to the effective date of the AD, this AD does not require that it be repeated. However, the AD does require that repetitive inspections be conducted thereafter at intervals not to exceed 6,000 hours time-in-service, and that other follow-on actions be accomplished when indicated. \n\nRequest to Extend the Compliance Time for Slat Adjustment \n\n\tOne commenter requests that the compliance time for adjustment of the stop clearance, as specified in paragraph (a)(2) of the proposal, be extended from the proposed 500 hours time-in- service to 3,000 hours time-in-service. This commenter asserts that the time for accomplishing this adjustment of the slats with incorrect clearance at the overtravel stop should not be more stringent than the time for accomplishing the replacement of the rotary actuator if no clearance is found to exist (specified in proposed paragraph (a)(3) as 3,000 hours time-in-service). \n\n\tThe FAA does not concur with the commenter's request to extend the compliance time for the slat adjustment; nor does the FAA agree that the compliance time for adjustment of the slats is more stringent than that for replacement of the actuator and gearbox. Paragraph (a)(2) of the AD requires the proper adjustment of the stop clearance within 500 flight hours after the initial inspection if that inspection reveals that some clearance exists, but not the correct clearance; the inspection is then to be repeated thereafter at intervals of 6,000 hours time-in-service. However, the FAA points out that paragraph (a)(3) of the AD requires adjustment of the stop clearance immediately (prior to further flight) if the inspection reveals that no clearance exists; afterthis adjustment is accomplished, the replacement of the actuator and gearbox is required within 3,000 hours time-in-service. For cases where some clearance exists, the FAA finds a compliance time of 500 flight hours to be appropriate and warranted, since some clearance may continue to deteriorate until no clearance exists.\n\nRequests to Defer Initial Inspections \n\n\tTwo commenters request that the compliance time for the initial inspections be deferred until Model 767 series airplanes have accumulated 10,000 total hours time-in-service, as recommended in Boeing Service Bulletin 767-27A0137, Revision 1, dated November 30, 1995. One of these commenters states that the history of the Model 767 fleet has shown that, for airplanes that have accumulated 10,000 total hours time-in-service or less, the amount and location of corrosion in the rotary actuators does not adversely affect their strength or function. \n\n\tThe FAA concurs with the commenters' request to defer the initial inspections. The FAA has reviewed and approved Revision 1 of Boeing Service Bulletin 767-27A0137, dated November 30, 1995, as discussed below. The FAA has revised the compliance time of the initial inspection requirements of paragraphs (a), (b), and (c) of the final rule to state "prior the accumulation of 10,500 total hours time-in-service since date of manufacture, or within 500 hours time-in-service after the effective date of this AD, whichever occurs later . . ." to coincide with the recommendations of the service bulletin. \n\nRequests to Reference Boeing Service Bulletin 767-27A0137 \n\n\tSeveral commenters request that the FAA reference Boeing Service Bulletin 767-27A0137, Revision 1, dated November 30, 1995, as the appropriate source of service information for accomplishing the actions required by the proposal. \n\n\tThese commenters point out that, even though the proposal references the Boeing 767 Airplane Maintenance Manual (AMM), Chapter 27-81-20, as the appropriate source of service information, the proposed actions and compliance times of the proposal appear to be consistent with the recommendations of Boeing Service Bulletin 767-27A0137. Two of these commenters point out that the procedures described in the Boeing 767 AMM for accomplishing the inspection requirements of the proposal are not as detailed as those described in Boeing Service Bulletin 767- 27A0137. The commenters contend that referencing the subject service bulletin will eliminate the operators' confusion as to which slats are to be inspected. \n\n\tOne of these commenters states that many operators have already accomplished the recommendations of Boeing Service Bulletin 767-27A0137, since it has been available for some time now. However, without specific reference to this service bulletin in the proposal, operators will be hesitant to indicate compliance with the AD without first submitting a request for an alternative method of compliance. \n\n\tThe FAA concurs with the commenters' request toreference Boeing Service Bulletin 767- 27A0137 as the appropriate source of service information. The FAA has reviewed and approved Boeing Service Bulletin 767-27A0137, Revision 1, dated November 30, 1995. The service bulletin describes procedures for: \n\n\t1. A visual inspection to verify proper clearance of the overtravel stop; \n\t2. Adjustment of the stop clearance, and replacement of the rotary actuator and adjacent offset gearbox, if necessary; \n\t3. Repetitive visual inspections to detect external signs of internal corrosion of the rotary actuator of the outboard leading edge slat; \n\t4. Replacement of a certain earlier model rotary actuator with a certain later model rotary actuator, for certain airplanes; \n\t5. Visual inspection(s) to verify proper installation of the control rods of the outboard leading edge slats; and \n\t6. Tightening of the bolts or installing a new lockwire, if any bolt is loose or any lockwire is missing. \n\n\tThe final rule has been revised to include this service bulletin as an additional source of appropriate service information. The final rule also has been revised to indicate the specific numbers of the outboard leading edge slats that are to be inspected. \n\n\tOperators should note that although the Boeing service bulletin indicates that certain procedures may be accomplished in accordance with an "operator's equivalent procedure," this AD does not permit such procedures to be used unless they have been approved as an alternative method of compliance under the provisions of paragraph (d) of the final rule. Since procedures may vary from operator to operator, the FAA would have no way of knowing whether an "equivalent" procedure would provide an acceptable level of safety unless it has been reviewed and verified in accordance with the alternative method of compliance approval process. New NOTES 3, 4, and 5 have been added to this final rule to clarify this information. \n\nRequest to Reference Original Version of ServiceBulletin \n\n\tTwo commenters request that the proposed rule be revised to cite the original version of Boeing Alert Service Bulletin 767-27A0137, dated May 18, 1995, as an additional source of service information for accomplishing the actions specified in the AD. The FAA concurs and has revised the final rule to include a new "NOTE 2" to clarify this point. \n\nRequest to Revise the Reference to "New" Actuator \n\n\tSeveral commenters note that paragraphs (b)(1)(i), (b)(2)(i), and (b)(2)(ii) of the proposal specify replacement of the actuator with a "new" actuator having part number (P/N) 256T2120-5 or later. One of these commenters suggests that, in lieu of the word "new," the language in the AD should use the term "serviceable," which would be a more accurate description. This same commenter states that a serviceable actuator, having P/N 256T2120-5 or later, is sufficient when it has been inspected according to the Component Maintenance Manual.\n\n\tThe FAA concurs with this suggestion and has revised the relevant wording of the final rule. \n\nRequest to Revise the Cost Impact Statement \n\n\tOne commenter questions the FAA's cost estimate presented in the preamble to the notice. The commenter points out that the cost estimate did not include the cost of replacement of the rotary actuators, having part number (P/N) 256T2120-3 or earlier, with a new rotary actuator, having P/N 256T2120-5 or later. \n\n\tThe FAA finds that clarification of the costs associated with the requirements of this AD is necessary. The FAA points out that the economic analysis of the AD is usually limited only to the cost of actions actually required by the rule. It does not consider the costs of "on condition" actions (e.g., "replace if any sign of internal corrosion is detected"), since those actions would be required to be accomplished, regardless of AD direction, in order to correct an unsafe condition identified in an airplane, and to ensure operation of that airplane in an airworthycondition, as required by the Federal Aviation Regulations. \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 612 Model 767 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 213 airplanes of U.S. registry will be affected by this AD, that it will take approximately 14 work hours per airplane to accomplish the required inspections, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $178,920, or $840 per airplane, per inspection cycle. \n\n\tThe cost impact figure discussed above is based on assumptionsthat 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 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\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\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\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\t2. Section 39.13 is amended by adding the following new airworthiness directive: