RULES and REGULATIONS

DEPARTMENT OF TRANSPORTATION Federal Aviation Administration 14 CFR Part 39 [Docket No. 89 -NM-223 -AD; Amendment 39 -6603] Airworthiness Directives; Airbus Industrie Model A300 Series Airplanes Tuesday, May 15, 1990 AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Final rule. SUMMARY: This amendment adopts a new airworthiness directive (AD), applicable to certain Airbus Industrie Model A300 series airplanes, which requires repetitive inspections to detect cracks in the outer shroud box aft hinge brackets, and repair, if necessary. This amendment is prom pted by reports of cracks found during routine maintenance checks. This condition, if not corrected, could lead to failure of these brackets and subsequent structural and system damage to the airplane. EFFECTIVE DATE: June 19, 1990. ADDRESSES: The applicable service information may be obtained from Airbus Industrie, Airbus Support Division, Avenue Didier Daurat, 31700 Blagnac, France. This information may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 17900 Pacific Highway South, Seattle, Washington, or the Standardization Branch, 9010 East Marginal Way South, Seattle, Washington. FOR FURTHER INFORMATION CONTACT:Mr. Greg Holt, Standardization Branch, ANM- 113; telephone (206) 431 - 1918. Mailing address: FAA, Northwest Mountain Region, 17900 Pacific Highway South, C-68966, Seattle, Washington 98168. SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal Aviation Regulations to include a new airworthiness directive, applicable to certain Airbus Industrie Model A300 series airplanes, which requires re-petitive inspections to detect cracks in the outer shroud box aft hinge brackets, and repair if necessary, and eventual

modification, was published in the Federal Register on December 7, 1989 (54 FR 50515) . Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. One commenter requested that the final rule be clarified by adding, “if no crack(s) have been found during the initial inspection,” to the repetitive inspection interval requirement of 1,000 landings to ensure that the repetitive inspections would be required only in instances when cracks were not found. The FAA concurs. In order to avoid confusion or any possibility of

misunderstanding, the final rule has been revised to indicate that the repetitive inspections are only required if no cracks are found. The commenter also noted the inconsistencies between the proposed rule and the service bulletin and the French Airworthiness Directive (AD). Specifically, the commenter noted that these airplanes should be allowed to continue to fly, if only one bracket is cracked, in which case repetitive inspections would be conducted every 50 landings, as specified in the service bulletin and the French AD. The FAA does not concur. The FAA has determined that airworthiness cannot be ensured if airplanes are permitted further flight with one cracked bracket. The potential exists for the remaining brackets to sustain the load of the cracked bracket, thus placing inordinate stress on the remaining brackets, and eventually also causing them to crack. Another commenter requested that the proposed rule be withdrawn because the com pliance time of two years to replace all existing aluminum alloy brackets with steel brackets is too restrictive for a nonsafety related issue. Additionally, two commenters questioned the justification for the proposed rule, since cracks in shroud boxes do not lead to an unsafe condition. The commenters viewed replacement of brackets as an economic issue rather than a safety issue. The FAA does not concur. Bracket failure may cause vertical movement of the inboard shroud box structure in the immediate area and subsequent fouling of the inboard flap top skin. This contact would be progressively loaded during airbrake deployment. When a bracket fails, the loads may transfer to the remaining supports and they may also eventually crack. However, the FAA has reevaluated the circumstances which prom pted the proposal to replace the aluminum alloy brackets with steel brackets, and has reconsidered the mandatory replacement requirement. The FAA has determined that the high degree of reliability of the inspection methods, and the frequency of the inspection intervals, as proposed, will ensure that cracks will be detected before airworthiness is com promised. Accordingly, the final rule has been revised to delete this requirement. Because of the deletion of this requirement, the final rule provides for an optional replacement of the aluminum alloy brackets with new improved steel brackets, in which case the requirement for the repetitive inspections would be terminated. The economic analysis paragraph below has been revised to reflect only the cost for repetitive inspections. Since the proposed mandatory replacement requirement has been deleted from the final rule, related parts costs have also been deleted from the economic analysis. “Close visual inspection”, has been changed to read, “detailed visual inspection,” to clarify the terminology in paragraphs A. and B. of the final rule to more accurately describe the type of visual inspection required.After careful review of 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 noted above. These changes will neither increase the economic burden on any operator nor increase the scope of the AD. It is estimated that 66 airplanes of U.S. registry will be affected by this AD, that it will take approximately 4 manhours per airplane to accomplish the required actions, and that the average labor cost will be $40 per manhour. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $10,560. 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 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. For the reasons discussed above, I certify that this action (1) Is not a “major rule” under Executive Order 12291 ; (2) is not a “significant rule” under DOT Regulatory Policies and Procedures (44 FR 11034; February 2 6, 1979); and (3) will not have a significant economic im pact, 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 is contained in the regulatory docket. A copy of it may be obtained from the Rules Docket. List of Subjects in 14 CFR Part 39 Air transportation, Aircraft, Aviation safety, Safety. Adoption of the Amendment Accordingly, 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: 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 . § 39.13 [Amended] 2. Section 39.13 is amended by adding the following new airworthiness directive: Airbus Industrie: Applies to Model A300 series airplanes, as listed in Airbus Industrie Service Bulletin A300- 57 - 142, dated December 17, 1986, certificated in any category. Com pliance is required as indicated, unless previously accomplished.To prevent failure of the outer shroud box aft hinge brackets, accomplish the following:

A. Prior to the accumulation of 5,000 landings, or within the next 300 landings after the effective date of this AD, whichever occurs later, perform a detailed visual inspection to detect cracks in the outer shroud box aft hinge brackets, in accordance with Airbus Industrie Service Bulletin A300 - 57 - 142, dated December 17, 1986. B. If no cracks are found, repeat the inspection required by paragraph A., above, at intervals not to exceed 1,000 landings. C. If cracks are found, prior to further flight, perform a detailed visual inspection to detect cracks or damage in the remaining supports (shroud box forward hinge brackets, inner shroud box forward attachments, and the attachment brackets at the inboard end of the inner box shroud box), in the inner and outer shroud box structure in the vicinity of the failed bracket, and the top skin of the inboard flap, in accordance with the Airbus Industrie Service Bulletin A300 - 57 - 142, dated December 17, 1986. 1. If cracks or damage is found in the remaining supports, the inner and outer shroud box structure, or top skin of the inboard flap, repair prior to further flight in a manner approved by the Manager, Standardization Branch, ANM- 113, FAA, Northwest Mountain Region. 2 . If any bracket is found to be cracked, damaged, or otherwise failed, replace the bracket with a serviceable part prior to further flight.

a. If the bracket is replaced with an im proved steel bracket (Modification 6661H1033), in accordance with Airbus Industrie Service Bulletin A300 - 57 - 142, dated December 17, 1986, or Airbus Industrie Service Bulletin A300 - 57 - 143, Revision 2, dated July 10, 1989, the repetitive inspection of that bracket, as required by paragraph A., above, may be terminated. b. If the bracket is replaced with other than an improved steel bracket, repeat the inspection required by paragraph A. above, prior to the accumulation of 5,000 landings on the new bracket, and thereafter at intervals not to exceed 1,000 landings. D. An alternative means of com pliance or adjustment of the com pliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Standardization Branch, ANM- 113, FAA, Northwest Mountain Region. Note: The request should be forwarded through an FAA Principal Maintenance Inspector (PMI), who will either concur or comment and then send it to the Manager, Standardization Branch, ANM- 113. E. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes 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 Airbus Industrie, Airbus Support Division, Avenue Didier Daurat, 31700 Blagnac, France. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 17900 Pacific Highway South, Seattle, Washington, or the Standardization Branch, 9010 East Marginal Way South, Seattle, Washington. This amendment becomes effective June 19, 1990. Issued in Seattle, Washington, on May 4, 1990. Steven B. Wallace, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.