AD 2003-10-06 Airworthiness Directives; Boeing Model 747 Series Airplanes

Models named: 747 series. Read the applicability below — it usually turns on serial or part numbers too.

Model 747 series airplanes, line numbers 1 through 1255 inclusive, certificated in any category. Note 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 (f) 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.

Required as indicated, unless accomplished previously,” which appears in every AD. Therefore, no change to the final rule is necessary in this regard. Request To Reference Existing AD and Relation to New AD One commenter states that the proposed AD affects an area that is the subject of AD 94-15-18, amendment 39-8989 (59 FR 41233, August 11, 1994), and Boeing 747 Supplemental Structural Inspection Document (SSID) D6-35022, and can affect Structurally Significant Item (SSI) F-39E. The commenter asks that any related requirements between the new AD and the existing AD be discussed. The commenter adds that the effect of repairs, modifications, and duplication of inspections done per the existing AD should be reviewed, and a determination made of whether one set of AD requirements meets the existing AD requirements. We have been informed by the manufacturer that the Boeing 747 SSID is being revised to remove the portions of SSI F-39 inspections that are required by this AD. This revision to the Boeing 747 SSID may be approved as an alternative method of compliance to AD 94-15-18, which would eliminate the potential for duplication of inspections. In addition, repairs and modifications done per the existing AD will not be affected by the requirements in this AD. Therefore, no change to the final rule is necessary in this regard. Request To Withdraw Proposed AD One commenter disagrees that the cracking found in the upper corners of the aft lower cargo door cutout constitutes an unsafe condition that warrants regulatory action. The commenter states that the cracks reported by Boeing in the referenced service bulletin were small and did not pose an imminent threat of rapid depressurization. The commenter notes that the robust structure of the lower lobe cargo door cutout mitigates threats from minor skin cracks. The commenter adds that cracks found on the commenter's airplanes were found as a result of routine maintenance inspection, proving that existing inspection and maintenance programs will detect cracking in the subject areas before an unsafe condition exists. The commenter states that a minor revision to the maintenance program would ensure adequate crack detection, without the need for additional regulatory action. We do not agree with the commenter. Cracks over one inch in length have been found in both the fuselage skin and the adjacent bear strap. If cracks propagate into the sill chord, rapid decompression could occur. The door hinge fairing also covers up the area of cracking, making it unlikely that all cracks will be detected by routine maintenance inspections. No change to the final rule is necessary in this regard. Request To Change Cost Impact Analysis One commenter states that the FAA estimate of approximately 3 work hours to accomplish the proposed inspection does not include the time required to gain access and close-up. In the case of this AD, some of the associated access and close-up time, including removing and re-installing fasteners and fittings, is not incidental, and is only required for this particular inspection procedure. The commenter notes that those costs should be included in the cost impact analysis. The commenter adds that the other costs, such as access and closeup of seats, carpet, cargo handling equipment, floor panels, and insulation blankets, may be incidental during some scheduled heavy maintenance inspections, but would not be incidental if done during a special maintenance visit. We do not agree to change the number of estimated work hours for the inspections. The number of work hours necessary to accomplish the inspections, specified as 3 in the cost impact information, is consistent with the service bulletin. This number represents the time necessary to perform only the inspections actually required by this AD. We recognize that, in accomplishing the requirements of any AD, operators may incur additional costs due to special circumstances when scheduling maintenance visits. However, because maintenance schedules vary significantly from operator to operator, the hours necessary for access and closeup time, including removing and re-installing fasteners, are almost impossible to calculate. Therefore, no change is made to the final rule in this regard. Requests To Change Compliance Time One commenter asks that the compliance time specified in paragraph (a)(2) of the proposed AD be changed from “For airplanes with 13,000 or more total flight cycles as of the effective date of this AD: Do the inspection within 1,000 flight cycles or 1 year after the effective date of this AD, whichever is first,” to “For airplanes with 13,000 or more flight cycles as of the effective date of this AD: Do the inspection within 1,000 flight cycles after the effective date of this AD.” If a calendar-driven timetable is used, to prevent unnecessary special maintenance visits, the commenter asks that paragraph (a)(2) be changed to, “For airplanes with 13,000 or more flight cycles as of the effective date of this AD: Do the inspection within 1,000 flight cycles or 18 months after the effective date of this AD, whichever occurs first.” The commenter states that the subject cracking is caused by fatigue, and such cracking is attributed to cyclic loading, not calendar time, so requiring a fatigue-related inspection based on calendar time is not justified. The commenter adds that most 747 operators currently use C-check inspection intervals of 18 months. Due to this fact, the commenter notes that the one-year initial inspection interval specified in paragraph (a)(2) would impose special inspection visits on one-third of the fleet. A second commenter also asks that the compliance time specified in paragraph (a)(2) of the proposed AD be changed to “For airplanes with 13,000 or more flight cycles as of the effective date of this AD: Do the inspection within 1,300 flight cycles or 18 months after the effective date of this AD, whichever occurs first.” The commenter adds that this compliance time supports maintenance flow. The same commenter asks that the compliance time in paragraph (a)(1) of the proposed AD be changed to “For airplanes with less than 13,000 flight cycles as of the effective date of this AD: Do the inspection prior to the accumulation of 13,000 flight cycles or within 1,300 flight cycles after the effective date of this AD, whichever occurs later.” The commenter adds that this compliance time results in inspections and rework during scheduled A-checks. We do not agree with the commenters. We have determined that a 1,000 flight cycle grace period for airplanes having more than 13,000 total flight cycles may not provide for an adequate level of safety for airplanes with low cycle usage. While there is some technical merit that a calendar-based compliance time should not apply to a fatigue issue, we have determined that the 1-year compliance time will ensure that the required inspections are completed in a timely manner, in particular, on airplanes that are well above the 13,000 total flight cycle threshold. In developing an appropriate compliance time for the actions required by this AD, we considered not only those safety issues, but the manufacturer's recommendations and the practical aspect of accomplishing the inspection within an interval paralleling normal scheduled maintenance for the majority of affected operators. In light of the factors described previously, we consider “within 1,000 flight cycles or 1 year after the effective date of this AD, whichever occurs first,” to be an appropriate compliance time wherein safety will not be adversely affected. No change to the final rule is necessary in this regard. Additional Change to Final Rule Because the language in Note 3 of the proposed AD is regulatory in nature, that note has been redesignated as paragraph (b) of this final rule. Conclusion After 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. Cost Impact There are approximately 1,129 airplanes of the affected design in the worldwide fleet. The FAA estimates that 275 airplanes of U.S. registry will be affected by this AD, that it will take approximately 3 work hours per airplane to accomplish the inspection, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of this required inspection on U.S. operators is estimated to be $49,500, or $180 per airplane, per inspection cycle. The 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. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close-up, planning time, or time necessitated by other administrative actions. Regulatory Impact The regulations adopted herein will not have a substantial direct effect 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, it is determined that this final rule does not have federalism implications under Executive Order 13132. 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. List of Subjects in 14 CFR Part 39 Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. Adoption of the Amendment Accordingly, 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: PART 39—AIRWORTHINESS DIRECTIVES 1. The authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. 106(g), 40113, 44701. § 39.13 [Amended] 2. Section 39.13 is amended by adding the following new airworthiness directive: 2003-10-06 Boeing: Amendment 39-13151. Docket 2000-NM-377-AD.