AD 2001-16-07

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747-400 and 767 series airplanes, that requires modification of the core cowl assemblies of the engines. This action is necessary to prevent failure of the core cowl latches during an engine fire, and consequent in-flight separation of an engine core cowl and its strut fire barrier from the airplane. This action is intended to address the identified unsafe condition.

Final rule.

2001-16-07 Boeing: Amendment 39-12375. Docket 2000-NM-275-AD. \n\n\tApplicability: Model 747-400 and 767 series airplanes, certificated in any category, equipped with General Electric CF6-80C2 series engines; as listed in Boeing Service Bulletin 747-71-2285 or 767-71-0088, both dated October 8, 1998. \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 (c) 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 failure of the core cowl latches during an engine fire, and consequent in-flight separation of an engine core cowl and its strut fire barrier from the airplane, accomplish the following: \n\nModification \n\n\t(a) Within 36 months after the effective date of this AD: Modify the left-and right-hand core cowl assemblies of the engines per the Accomplishment Instructions of Boeing Service Bulletin 747-71-2285 (for Model 747-400 series airplanes) or 767-71-0088 (for Model 767 series airplanes), both dated October 8, 1998. \n\n\tNote 2: The Boeing service bulletins reference ROHR Service Bulletin TBC/80C2-NAC-71-028, dated August 1, 1998, as an additional source of service information for accomplishment of the modification. \n\nSpares \n\n\t(b) As of 6 months after the effective date of this AD, no one may install an aluminum core cowl assembly, part number 224-2301-513(left-hand) or 224-2302-539 (right-hand), on any airplane. \n\nAlternative Methods of Compliance \n\n\t(c) An 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. Operators shall submit their requests through an appropriate FAA Principal Operations Inspector or Principal Maintenance Inspector, as applicable, who may add comments and then send the request and any comments 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\nSpecial Flight Permits \n\n\t(d) Special 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(e) The actions shall be done in accordance with Boeing Service Bulletin 747-71-2285, dated October 8, 1998; or Boeing Service Bulletin 767-71-0088, dated October 8, 1998; 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 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\nEffective Date \n\n\t(f) This amendment becomes effective on September 24, 2001.

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 747-400 and 767 series airplanes was published in the Federal Register on December 5, 2000 (65 FR 75881). That action proposed to require modification of the core cowl assemblies of the engines. \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\n\tOne commenter states that it does not own or operate any of the subject airplanes and, thus, offers no additional comment on the proposed AD. \n\nRequests To Extend Compliance Time \n\n\tThree commenters request that the FAA extend the compliance time for the proposed modification. One of the commenters requests that the FAA extend the compliance time from 24 months to 36 months after the effective date of this AD, due to itsconcerns about availability of necessary parts for the modification. The other two commenters request that the FAA extend the compliance time to 48 months after the effective date of this AD. One of these commenters is also concerned about parts availability, while the other commenter wants the extension so that it may accomplish the modification during its regularly scheduled "C" and "D" checks. \n\n\tThe FAA concurs with the one commenter's request to extend the compliance time to 36 months after the effective date of this AD. We have determined that extending the compliance time to 36 months will allow a sufficient supply of parts to be made available for the required modification without adversely affecting safety. We have revised paragraph (a) of this final rule accordingly. \n\n\tWe do not concur with the other commenters' requests to extend the compliance time for the modification to 48 months. With regard to parts availability, as stated above, we find that a 36-month compliancetime will be adequate for a sufficient quantity of parts to be available. With regard to extending the compliance time to allow the modification to be accomplished at a "C" or "D" check, we have already considered factors such as operators' maintenance schedules in setting a compliance time for the required modification and determined that 36 months is an appropriate compliance time in which the modification may be accomplished during scheduled airplane maintenance for the majority of affected operators. Since maintenance schedules vary from operator to operator, it would not be possible to guarantee that all affected airplanes could be modified during scheduled maintenance, even with a compliance time of 48 months. In any event, we find that 36 months represents the maximum time wherein the affected airplanes may continue to operate prior to modification without compromising safety. No further change to the final rule is necessary in this regard. \n\nRequest To Withdraw Proposed RuleOne commenter requests that the FAA withdraw the proposed rule. In the proposed rule, we explained that, in the event of an engine fire, the core cowl latches may fail, and opening of the core cowls breaches the engine fire containment design and could allow the fire to spread to the strut and wing of the airplane. The commenter states that, following extensive review of the engine cowling configuration, it cannot see that the core cowls would open during an engine fire even if the frame is weakened, because the trailing edge of the thrust reverser covers up the leading edge of the core cowl. Therefore, the commenter does not agree that there is risk of a fire spreading to the strut. The commenter further requests that we withdraw the proposed rule because the total cost of the modification that would be required by this AD for its fleet would be very expensive. \n\n\tWe do not concur with the commenter's request to withdraw the proposed rule. With regard to the commenter's doubtsabout whether failure of the core cowl latches is an unsafe condition, we acknowledge that the commenter is correct when it states that the trailing edge of the thrust reverser covers the leading edge of the core cowl. However, in the event of an engine fire when the aluminum structure supporting the steel latches holding the core cowls closed is significantly weakened, the structural continuity between the hinges at the top of the core cowl and the latches at the bottom no longer exists. Therefore, the structural integrity of the attachment of the core cowl to the airplane is compromised, and aerodynamic loads will force the core cowls to open and subsequently detach from the airplane. As explained in the NPRM, this condition could allow the engine fire to spread to the strut and wing. We have determined that this risk of a fire propagating to the strut and wing is significant and constitutes an unsafe condition that must be addressed. \n\n\tWith regard to the commenter's concern about the cost of the AD, we acknowledge that there are relatively high costs associated with the required modification. For operators with many affected airplanes, the cost could run into millions of dollars. However, in considering whether to issue this AD, we conducted a cost analysis and determined that the costs of the modification required by this AD are commensurate with the level of risk involved, and it is necessary to issue this AD to ensure the continued safety of the affected airplanes. \n\n\tNo change to the final rule is necessary in this regard. \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 change previously described. The FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD. \n\nCost Impact \n\n\tThere are approximately 563 Model 747-400 and 767 series airplanes of the affected design in the worldwide fleet. \n\n\tThe FAA estimates that 14 Model 747-400 series airplanes of U.S. registry will be affected by this AD, that it will take approximately 168 work hours (42 per engine) per airplane to accomplish the required modification, and that the average labor rate is $60 per work hour. Required parts will cost approximately $84,732 ($21,183 per engine) per airplane. Based on these figures, the cost impact of the modification required by this AD on U.S. operators of Model 747-400 series airplanes is estimated to be $1,327,368, or $94,812 per airplane. \n\n\tThe FAA estimates that 64 Model 767 series airplanes of U.S. registry will be affected by this AD, that it will take approximately 84 work hours (42 per engine) per airplane to accomplish the required modification, and that the average labor rate is $60 per work hour. Required parts will cost approximately $42,366 ($21,183 per engine) per airplane. Based on these figures, the costimpact of the modification required by this AD on U.S. operators of Model 767 series airplanes is estimated to be $3,033,984 or $47,406 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. 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. \n\nRegulatory Impact \n\n\tThe 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. \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: \n\n\tAuthority: 49 U.S.C. 106(g), 40113, 44701. \n\nSec. 39.13 (Amended) \n\n\t2. Section 39.13 is amended by adding the following new airworthiness directive: