AD 94-01-08

This amendment adopts a new airworthiness directive (AD) that is applicable to certain McDonnell Douglas Model DC-9 and C-9 (military) series airplanes. This action requires inspections to detect cracking in the ventral aft pressure bulkhead, and repair, if necessary. This amendment is prompted by reports of cracking found in the ventral aft pressure bulkhead on several airplanes. The actions specified in this AD are intended to prevent the propagation of cracks in the ventral aft pressure bulkhead, which could lead to failure of the bulkhead and subsequent rapid decompression of the airplane.

Final rule; request for comments.

94-01-08 McDONNELL DOUGLAS: Amendment 39-8790. Docket 93-NM-224-AD. \n\n\tApplicability: Model DC-9 and C-9 (military) series airplanes, as listed in McDonnell Douglas DC-9 Alert Service Bulletin A53-264, dated December 22, 1993; equipped with a ventral aft pressure bulkhead web composed of 2014-T6 material that is 0.042 inch thick; certificated in any category. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent failure of the aft pressure bulkhead due to cracking, accomplish the following: \n\n\t(a)\tFor airplanes on which the procedures specified in McDonnell Douglas DC-9 Service Bulletins 53-26 and A53-144, or production equivalent, have not been accomplished (Group I airplanes): Upon the accumulation of 50,000 total landings, or within 30 days after the effective date of this AD, whichever occurs later, conduct an initial visual, low frequency eddy current, and high frequency eddy current inspection to detect cracks in the ventral aft pressure bulkhead, in accordance with McDonnell Douglas DC-9 Alert Service Bulletin A53-264, dated December 22, 1993. \n\n\t\t(1)\tIf no crack is detected during any of the inspections, repeat these inspections at intervals not to exceed 1,500 landings. \n\n\t\t(2)\tIf any crack is detected during any of the inspections, prior to further flight, repair in accordance with a method approved by the Manager, Los Angeles Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. \n\n\t(b)\tFor airplanes on which the procedures specified in McDonnell Douglas DC-9 Service Bulletins 53-26 and A53-144, or production equivalent, have previously been accomplished (Group II airplanes): Upon the accumulation of 60,000 total landings, or within 60 days after the effective date of this AD, whichever occurs later, conduct an initial visual, low frequency eddy current, and high frequency eddy current inspection to detect cracks in the ventral aft pressure bulkhead, in accordance with McDonnell Douglas DC-9 Alert Service Bulletin A53-264, dated December 22, 1993. \n\n\t\t(1)\tIf no crack is detected during any of the inspections, repeat these inspections at intervals not to exceed 1,500 landings. \n\n\t\t(2)\tIf any crack is detected during any of the inspections, prior to further flight, repair in accordance with a method approved by the Manager, Los Angeles ACO, FAA, Transport Airplane Directorate. \n\n\t(c)\tWithin 10 calendar days after accomplishing the initial inspection required by paragraph (a) or (b) of this AD, as applicable, submit a report of inspection findings, both positive and negative, to the Manager, Los Angles ACO, FAA, Transport Airplane Directorate, 3229 East Spring Street, Long Beach, California 90806-2425; fax (310) 988-5210. The report must include the following information: \n\n\t\t(1)\tFactory serial number of the airplane \n\n\t\t(2)\tTotal time and flight cycles on the airplane; \n\n\t\t(3)\tA detailed description of the discrepancy finding; \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 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: 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 FAR 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 shall be done in accordance with McDonnell Douglas DC-9 Alert Service Bulletin A53-264, dated December 22, 1993. 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, P. O. Box 1771, Long Beach, California 90846-0001, Attention: Business Unit Manager, Technical Publications, C1-HDR (54-60). Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Los Angeles Aircraft Certification Office, FAA, Transport Airplane Directorate, 3229 East Spring Street, Long Beach, 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 January 28, 1994.

The FAA has recently received reports of cracking found in the ventral aft pressure bulkhead on several McDonnell Douglas Model DC-9 series airplanes. Two operators reported finding fatigue cracks on four airplanes in both the left- and right-hand side ventral aft pressure bulkhead web and doublers, between water lines (stations) Z=43.000 and Z=74.000. The length of the reported cracks found in the webs ranged from 5 inches to 48 inches. The webs of each of the cracked bulkheads on the subject airplanes were made of 2014-T6 material and were 0.042 inch thick. It is suspected that fatigue is the cause of the cracks. The affected airplanes had accumulated between 73,803 and 83,760 landings at the time of the crack findings. In each case, the cracking was found during inspections that were outside of the operator's normal maintenance program schedule. Currently, there is no requirement for regular inspection of the affected area of the bulkhead. Crackingin the ventral aft pressure bulkhead web or doublers, if allowed to propagate to a critical length, could lead to failure of the bulkhead, extensive structural damage, and subsequent rapid decompression of the airplane. \n\n\tThe FAA has reviewed and approved McDonnell Douglas DC-9 Alert Service Bulletin A53-264, dated December 22, 1993, that describes procedures for conducting repetitive visual, low frequency eddy current, and high frequency eddy current inspections to detect cracking in the ventral aft pressure bulkhead. The area of inspection includes the upper left and right sides of the ventral aft pressure bulkhead in the area of the finger doublers and web between stations Z=34.000 and Z=74.000, from the edge of the ventral doorway outboard and upward along the edge of the doublers. \n\n\tSince an unsafe condition has been identified that is likely to exist or develop on other Model DC-9 and C-9 (military) series airplanes of the same type design, this AD is being issued to prevent failure of the ventral aft pressure bulkhead due to cracking. This AD requires repetitive visual, low frequency eddy current, and high frequency eddy current inspections to detect cracking in the ventral aft pressure bulkhead. These inspections are required to be accomplished in accordance with the service bulletin described previously. Any cracks found are required to be repaired, prior to further flight, in accordance with a method approved by the FAA. Additionally, operators are required to submit a report of initial inspection findings to the FAA. \n\n\tThis is considered to be interim action until final action is identified, at which time the FAA may consider further rulemaking. \n\n\tSince a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days. \n\nComments Invited \n\n\tAlthough this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an 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 notice must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 93-NM-224-AD." The postcard will be date stamped and returned to the commenter. \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\tThe FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, 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 14 CFR part 39 of the Federal Aviation Regulations as follows: \n\nPART 39 - AIRWORTHINESS DIRECTIVES \n\n\t1.\tThe authority citation for part 39 continues to read as follows: \n\nAuthority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89. \n\n§ 39.13 - (Amended) \n\n\t2.\tSection 39.13 is amended by adding the following new airworthiness directive: