RULES and REGULATIONS

DEPARTMENT OF TRANSPORTATION 14 CFR Part 39 [Docket No. 89 -NM- 15 -AD; Amdt. 39 - 6152] Airworthiness Directives: McDonnell Douglas Model DC - 9 - 10 Through - 30 Series and C - 9 (Military) Airplanes, Equipped With a Non-Ventral Aft Pressure Bulkhead Friday, March 17, 1989 AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Final rule. SUMMARY: This amendment adopts a new airworthiness directive, applicable to certain McDonnell Douglas Model DC - 9 - 10 through - 30 series and C - 9 (Military) series airplanes equipped with a non-ventral aft pressure bulkhead, which requires both visual and high frequency eddy current inspection of the aft pressure bulkhead from the aft side. This amendment is prompted by a recent report of a crack in the aft pressure bulkhead tee cap. If this condition is not corrected, bulkhead tee cap cracks may develop, which could result in rapid depressurization of the fuselage in flight and cause severe structural damage to the airplane. DATE: Effective March 24, 1989. ADDRESSES: The applicable service information may be obtained from McDonnell Douglas Corporation, 3855 Lakewood Boulevard, Long Beach, California 90846, Attention: Director of Publications, C1 -L00 (54 - 60). This information may be examined at FAA, Northwest Mountain Region, 17900 Pacific Highway South, Seattle, Washington, or 3229 East Spring Street, Long Beach, California. FOR FURTHER INFORMATION CONTACT: Mr. Michael N. Asahara, DC9/MD80 Program Manager, Airframe Branch, ANM - 122L, FAA, Northwest Mountain Region, Los Angele s Aircraft Certification Office, 3229 East Spring Street, Long Beach, California 90806 -2425; telephone (213) 988 - 5321. SUPPLEMENTARY INFORMATION: On May 31, 1988, the FAA issued AD 88 - 13 - 09, Amendment 39 - 5954 ( 53 FR 21411 ; June 8, 1988), to require the structural inspection of the aft pressure bulkhead using low frequency eddy current inspection techniques from the forward side of the bulkhead of all McDonnell Douglas Model DC - 9 series airplanes. That AD was prompted by reports of cracks in the aft pressure bulkhead tee cap. This condition, if not corrected, could result in rapid depressurization of the fuselage, causing structural damage and possible loss of adjacent structures, including damage to control cables, with sub sequent loss of airplane control.Since issuance of AD 88 - 13 - 09, a DC - 9 operator reported finding a 24 -inch crack in the non-ventral aft pressure

bulkhead tee while performing an unscheduled heavy maintenance inspection. Preliminary analysis of the tee revealed that the cracks initiated at multiple sites on the forward surface of the upstanding leg of the tee as the result of metal fatigue due to bending and preloads. The crack was detected on an airplane having logged 36,079 landings, with 40,336 total hours on the fuselage. Fractrographic analysis revealed that the crack initiated approximately 12,000 landings prior to its discovery. In light of this new report of cracking, the FAA has determined that the initial inspection threshold for com

pliance with the inspection requirements of AD8 8 - 13 - 09 must be reduced to 25,000 landings on airplanes equipped with non-ventral aft pressure bulkheads in order to adequately detect cracking in a timely manner. The FAA canvassed the affected airline operators, through the Air Transport Association (ATA) of America, and McDonnell Douglas, to ascertain their experience with the low f requency eddy

current inspection from the forward side of the bulkhead, as an option provided in AD 88 - 13 - 09. From information supplied by those groups, the FAA has determined that, due to the complexity and difficulty in performing that ty pe of inspection, the results may not be reliable and, therefore, the inspection may not be effective. The FAA has determined that a high frequency eddy current inspection of

the 5910163 - 91 and - 92 attach tee from the aft side of the bulkhead, coupled with an optically aided visual inspection, will more adequately detect cracking in the attach tee area. In addition, the FAA has determined that sealant must be removed from the inspection area prior to inspection. Further, because of the differences in the eddy current inspection equipment sensitivity, the FAA has determined that the interval between inspections of the 5910163 - 91 and - 92 attach tees must be reduced to 500 landings. The FAA has determined that, due to the multip le - site nature of the reported cracking, continued operation of airplanes with cracks is unacceptable. Accordingly, this action does not permit the interim repair for certain cracks as currently described in paragraph C.2.a. of AD 88 - 13 - 09. The FAA has reviewed and approved McDonnell Douglas Alert Service Bulletin A57 -231, dated February 24, 1989, which describes high frequency eddy current inspection of the attach tee area, and repairs or replacement, if necessary. Since this unsafe condition may exist or develop on other airplanes of the same ty pe design equipped with a non-ventral aft pressure bulkhead, this AD requires repetitive high frequency eddy current inspection of the 5910163 - 91 and - 92 attach tee, coupled with repetitive optically aided visual inspections of the attach tee from the aft side of the bulkhead, and repair or replacement, if necessary. Subsequent inspections are also required after any repair or replacement. Additionally, affected operators are required to remove sealant from the inspection area prior to inspection. The requirements of this AD differ from and replace the requirements of AD 88 - 13 - 09 for airplanes equipped with non-ventral aft pressure bulkheads by: (1) Deleting the option for low f requency eddy

current inspections from the forward side of the bulkhead; (2) lowering the initial inspection threshold called out in AD 88 - 13 - 09 to 25,000 landings; (3) eliminating the interim repair provided by that AD; and (4) eliminating the optional inspections from the forward side of the bulkhead. Since a situation exists that requires immediate adoption of this regulation, it is found that notice and public procedurehereon are impracticable, and good cause exists for making this amendment effective in less than 30 days.

The FAA is currently preparing a similar action to address revised inspection requirements for Model DC - 9 series airplanes equipped with a ventral aft pressure bulkhead. However, the proposed compliance time would not preclude a period for public comment. (Therefore, that action will appear as a Notice of Proposed Rulemaking.) The 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 resp onsibilities 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. The FAA has determined that this regulation is an emergency regulation that is not considered to be major under Executive Order 12291 . It is impracticable for the agency to follow the procedures of Order 12291 with respect to this rule since the rule must be issued immediately to correct an unsafe condition in aircraft. It has been further determined that this document involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034; February 26, 1979). If this action is subsequently determined to involve a significant/major regulation, a final regulatory evaluation or analysis, as appropriate, will be prepared and placed in the regulatory docket (otherwise, an evaluation or analysis is not required). List of Subjects in 14 CFR Part 39 Aviation safety, Aircraft. Adoption of the Amendment 14 CFR § 39.13 Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends Section 39.13 of Part 39 of the Federal Aviation Regulations ( 14 CFR 39.13) as follows: PART 39

— [AMENDED]1. The authority citation for Part 39 continues to read as follows: Authority: 49 U.S.C. 1354(a), 1421 and 1423; 49 U.S.C. 106(g) (Revised Pub. L. 97 -449, January 12, 1983); and 14 CFR 11.89 . 14 CFR § 39.13 § 39.13 Amended] 2. By adding the following new airworthiness directive:McDonnell Douglas: Applies to Model DC - 9 - 10 through - 30 series and C - 9 (Military) series airplanes, equipped with

a non-ventral aft pressure bulkhead, certificated in any category. Comp liance required as indicated, unless previously accomplished. To prevent cracks which could result in structural failure of the nonventral aft ventral pressure bulkhead, accomplish the following: A. Prior to the accumulation of 25,000 landings or within 500 landings after the effective date of this AD, whichever occurs later, inspect the aft pressure bulkhead attach tee section, in accordance with the following procedures. 1. Remove any sealant from inspection area of the tee section that might hinder optically aided and high frequency eddy current inspections. Clean dirt, grease, and all foreign materials from inspection area using lint- free wipers and 1,1,1 trichloroethane solvent or equivalent; 2. Using an optically aided visual inspection technique, inspect the 5910163 - 89, - 93, - 94, and - 95 attach tees from the aft side of the bulkhead, in accordance with McDonnell Douglas Alert Service Bulletin A53 -231, dated February 24, 1989 (hereinafter referred to as ASB53 -231). Repeat this inspection thereafter at intervals not to exceed 1,500 landings; and 3. Using a high frequency eddy current inspection technique, in accordance with ASB53 -231, inspect the 5910163 - 91 and - 92 attach tees from the aft side of the bulkhead. Repeat this inspection thereafter at intervals not to exceed 500 landings. B. If cracks are found, prior to further flight, replace the cracked tee cap or repair by splicing in a section of tee cap with a new like or im

proved part, in ac cordance with McDonnell Douglas Service Rework Drawings SR09530001, Revision C, dated August 18, 1987, and SR09530001, Revision “Advance D”, dated October 29, 1987. Prior to the accumulation of 25,000 landings after the repair or replacement, resume the repetitive inspections in accordance with paragraph A., above. C. Compliance with the requirements of this AD constitutes terminating action for the requirements of AD 88 - 13 - 09, Amendment 39 - 5954, relating to airplanes equipped with non-ventral aft pressure bulkheads. Note.

—The requirements of AD 88 - 13 - 09 relating to airplanes with ventral aft pressure bulkheads are not affected by this AD. D. An alternate means of com pliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Los Angeles Aircraft Certification Office, FAA, Northwest Mountain Region. Note.

—The request should be forwarded through an FAA Principal Maintenance Inspector (PMI), w ho may add anycomments then send it to the Manager, Los Angeles Aircraft Certification Office.

E. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes unpressurized to a base in order to comply with the requirements of this AD. All persons affected by

this directive who have not already received the appropriate service documents from the manufacturer may obtain copies upon request to McDonnell Douglas Corporation, 3855 Lakewood Boulevard, Long Beach, California 90846, Attention: Director of Publications, C1 -L00 (54 - 60). These documents may be examined at FAA, Northwest Mountain Region, 17900 Pacific Highway South, Seattle, Washington, or 3229 East Spring Street, Long Beach, California. This amendment becomes effective March 24, 1 989. Issued in Seattle, Washington, on February 24, 1989. Leroy A. Keith, Manager, Transport Airplane Directorate, Aircraft Certification Service. 54 FR 11167 - 01, 1989