AD 96-16-04

This amendment supersedes an existing airworthiness directive (AD), applicable to certain McDonnell Douglas Model DC-9 and DC-9-80 series airplanes, Model MD-88 airplanes, and C-9 (military) airplanes, that currently requires repetitive inspections to detect fatigue cracking in the area of the attach tees of the ventral aft pressure bulkhead. This amendment requires revised inspection and repair procedures, and provides for terminating action. It also deletes Model MD-88 airplanes from the applicability of the rule. This amendment is prompted by reports of fatigue cracking found in the subject area. The actions specified by this AD are intended to prevent the propagation of fatigue cracking, which could lead to structural failure of the ventral aft pressure bulkhead and subsequent rapid depressurization of the airplane.

Final rule.

96-16-04 McDONNELL DOUGLAS: Amendment 39-9704. Docket 95-NM-186-AD. Supersedes AD 89-16-12, Amendment 39-6287 which superseded AD 88-13-09, Amendment 39-5954 which superseded AD 85-16-03, Amendment 39-5109 which superseded AD 85-06-03, Amendment 39-5014. \n\n\tApplicability: Model DC-9-10, -20, -30, -40, and -50 series airplanes; Model DC-9-81 (MD-81), DC-9-82 (MD-82) and DC-9-83 (MD-83) series airplanes; and C-9 (military) airplanes; equipped with a ventral aft pressure bulkhead; as listed in McDonnell Douglas Alert Service Bulletin A53-232, Revision 2, dated April 28, 1995; 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 the propagation of fatigue cracks that could result in structural failure of the ventral aft pressure bulkhead, accomplish the following: \n\n\t(a)\tAccomplish the requirements of either paragraph (a)(1), "OPTION I," or (a)(2), "OPTION II," of this AD in accordance with McDonnell Douglas Alert Service Bulletin A53-232, Revision 2, dated April 28, 1995. The initial inspection of either option must be accomplished at the applicable time specified in Table 1 of this AD. \n\nTABLE 1 \n\n\nTotal accumulated \nlandings as of the \neffective date of this AD\n\n\n\nInitial inspection\nLess than 35,000\nPrior to the accumulation of 36,500 \ntotal landings, or within 1,500 \nlandings after the effective date of \nthis AD, whichever occurs later\n \n35,000 or more\nWithin 300 landings after the \neffective date of this AD; or within \n3,500 landings after accomplishing \nthe last inspection performed in \naccordance with AD 89-16-12; \nwhichever occurs later \n\t\n\t\t(1)\tOPTION I: Accomplish the requirements of paragraphs (a)(1)(i), (a)(1)(ii), and (a)(1)(iii) of this AD. \n\n\t\t\t(i)\tConduct a low frequency eddy current inspection to detect cracks of the side areas above the floor between longerons 7 and 17 on fuselage left and right sides. Repeat this inspection at intervals not to exceed 1,500 landings. \n\n\t\t\t(ii)\tConduct an optically aided detailed visual inspection to detect cracks of the top and lower areas from longeron 7 left side to longeron 7 right side, and on the lower fuselage from longeron 17 to longeron 20 on fuselage left and right sides. Repeat this inspection thereafter at intervals not to exceed 1,500 landings. \n\n\t\t\t(iii)\tConduct an optically aided detailed visual inspection to detect cracks of the bottom area from longeron 20 left side to longeron 20 right side. Repeat this inspection thereafter at intervals not to exceed 3,500 landings. \n\n\t\t(2)\tOPTION II: Conduct both a high frequency and a low frequency eddy current inspection for cracks around the entire periphery of the fuselage from the forward side of the bulkhead. Repeat these inspections at intervals not to exceed 2,500 landings. \n\n\t(b)\tIf any cracked tee section is found during any inspection required by this AD, prior to further flight, accomplish the requirements of either paragraph (b)(1) or (b)(2) of this AD, in accordance with the procedures specified in McDonnell Douglas Alert Service Bulletin A53-232, Revision 2, dated April 28, 1995: \n\n\t\t(1)\tReplace the cracked tee section with a new like part. Once that replaced part has accumulated 35,000 landings, repeat the inspections required by paragraph (a) of this AD. Or \n\n\t\t(2)\tReplace the cracked tee section with an improved part, as specified in the alert service bulletin. Such replacement constitutes terminating action for the repetitive inspections of that section of the tee only. \n\n\t(c)\tReplacement of all six aft pressure bulkhead tee sections with new improved parts, in accordance with McDonnell Douglas Alert Service Bulletin A53-232, Revision 2, dated April 28, 1995, constitutes terminating action for the inspections required by this AD. \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, Los Angeles 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, Los Angeles ACO. \n\n\tNOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Los Angeles 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 McDonnell Douglas Alert Service Bulletin A53-232, Revision 2, dated April 28, 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 McDonnell Douglas Corporation, 3855 Lakewood Boulevard, Long Beach, California 90846, Attention: Technical Publications Business Administration, Department C1-L51 (2-60). Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Los Angeles Aircraft Certification Office, Transport Airplane Directorate, 3960 Paramount Boulevard, Lakewood, California; 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 September 4, 1996.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 89-16-12, amendment 39-6287 (54 FR 31649, August 1, 1989), which is applicable to certain McDonnell Douglas Model DC-9 and DC-9-80 series airplanes, Model MD-88 airplanes, and C-9 (Military) airplanes, was published in the Federal Register on August 1, 1989 (54 FR 31649). The action proposed to require revised inspection and repair procedures, and provide for terminating action. It also proposed to delete Model MD-88 airplanes from the applicability of the rule, since the terminating action was installed on those airplanes during production. \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 proposal. \n\nRequest to Allow Inspections at Current Intervals \n\n\tSeveral commenters oppose the proposed shorter inspection intervals. These commenters request that the proposal be revised to permit operators to continue to conduct inspections at the same frequency as was mandated previously by AD 89-16-12. The commenters contend that the proposed AD is founded on the FAA's statement that improved inspection methods are available and should be used. These commenters do not object to modernizing the inspection methods, but state that nothing supports the proposed increase in inspection frequency. The commenters maintain that the increase in the frequency of inspections will be disruptive to airline maintenance programs and scheduling, and this will have an adverse economic impact on operators. \n\n\tThe FAA does not concur with the commenters' request. After cracking of the ventral aft pressure bulkhead tees was found, the FAA issued AD 89-16-12 only as an interim measure to mandate some type of inspection on these tees. Because no inspection procedures had been developedat that time for inspecting these specific tees, the FAA required that operators inspect them using the same inspection methods -- and inspection intervals -- that already had been developed for inspecting non-ventral aft pressure bulkhead tees. (Those inspection methods and intervals were described in McDonnell Douglas Service Bulletin A53-231.) The FAA issued AD 89- 16-12 in the absence of any specific, pertinent technical data relative to appropriate inspections of ventral bulkhead tees, and considered that some type of inspection of these tees was better than none at all. Even at the time that AD 89-16-12 was issued, it was the FAA's intention to revise that AD once the manufacturer had developed inspection methods that were specific to ventral bulkhead tees. (The FAA explained this in the preamble to AD 89-16-12.) \n\n\tWhen McDonnell Douglas eventually developed inspections for the ventral bulkhead tees, it issued Service Bulletin A53-232, which contained the inspection instructions and recommended inspection intervals. The inspection intervals were shorter than those that had been recommended for non-ventral bulkhead tees. These shorter intervals were determined based on the crack growth rate of these specific tees, residual strength of uncracked tees, and the detectability of the cracking using the inspection method. The FAA reviewed and approved the technical material presented in Service Bulletin A53-232. \n\n\tBased on that material and other data gathered from the in-service fleet, the FAA has determined that: \n\n\t1. the structure of the ventral and non-ventral bulkheads differs enough to justify the difference in the inspection intervals of the associated attach tees; \n\n\t2. using the same inspection interval for both ventral and non-ventral attach tees cannot be technically justified; \n\n\t3. shorter repetitive inspection intervals are appropriate for the ventral attach tees; and \n\n\t4. the shorter inspection intervals will ensure that fatigue cracking at the attach tees positioned in the ventral aft pressure bulkhead is detected and corrected before cracking can grow to a critical length and jeopardize the integrity of the bulkhead. \n\n\tWhile operators may incur additional costs because of more frequent inspections and maintenance schedule changes, the FAA finds that these costs are necessary in order to ensure the continued airworthiness of these airplanes and the safety of the flying public. \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 as proposed. \n\nCost Impact \n\n\tThere are approximately 1,500 Model DC-9 and DC-9-80 series airplanes, and C-9 (military) airplanes of the affected design in the worldwide fleet. The FAA estimates that 1,000 airplanes of U.S. registry will be affected by this proposed AD. \n\n\tTo accomplish the actions specified as "OPTION I" of the AD will entail approximately 22 work hours per visual inspection and 12 work hours per low frequency eddy current inspection. The average labor rate is $60 per work hour. Based on these figures, the cost impact on U.S. operators who elect to accomplish OPTION I is estimated to be $2,040 per airplane per inspection cycle. \n\n\tTo accomplish the actions specified as "OPTION II" of the AD will entail approximately 8 work hours per high and low frequency eddy current inspection. The average labor rate is $60 per work hour. Based on these figures, the cost impact on U.S. operators who elect to accomplish OPTION II is estimated to be $480 per airplane per inspection cycle. \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. \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: \n\nAuthority: 49 U.S.C. 106(g), 40113, 44701. \n\n§ 39.13 - (Amended) \n\n\t2. Section 39.13 is amended by removing amendment 39-6287 (54 FR 31649, August 1, 1989), and by adding a new airworthiness directive (AD), amendment 39-9704, to read as follows: