AD 99-19-26

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Airbus Model A300 and A300-600 series airplanes, that currently requires inspections to detect cracks in Gear Rib 5 of the main landing gear (MLG) attachment fittings at the lower flange, and repair, if necessary. This amendment establishes repetitive inspection intervals for certain inspections required by the existing AD. This amendment also adds a requirement to modify Gear Rib 5 of the MLG attachment fittings, which constitutes terminating action for the repetitive inspections. This amendment is prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by this AD are intended to prevent fatigue cracking of the MLG attachment fittings, which could result in reduced structural integrity of the airplane.

Final rule.

99-19-26 AIRBUS INDUSTRIE: Amendment 39-11313. Docket 98-NM-249-AD. Supersedes AD 98-03-06, Amendment 39-10298.

Applicability: Model A300 series airplanes, as listed in Airbus Service Bulletin A300- 57-0234, Revision 01, dated March 11, 1998; and Model A300-600 series airplanes, as listed in Airbus Service Bulletin A300-57-6087, Revision 01, dated March 11, 1998; except airplanes on which Airbus Modification 11912 has been installed in production, or on which Airbus Modification 11932 has been accomplished; certificated in any category.

NOTE 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 (e) 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.

Compliance: Required as indicated, unless accomplished previously.

To prevent fatigue cracking of the main landing gear (MLG) attachment fittings, which could result in reduced structural integrity of the airplane, accomplish the following:

RESTATEMENT OF REQUIREMENTS OF AD 98-03-06

Inspections and Repair

(a) For Model A300 series airplanes that have accumulated more than 27,000 flight cycles as of March 9, 1998 (the effective date of AD 98-03-06, amendment 39-10298): Except as provided by paragraph (b) of this AD, within 40 flight cycles after March 9, 1998, perform a detailed visual inspection to detect cracks in Gear Rib 5 of the MLG attachment fittings at the lowerflange, in accordance with Airbus Service Bulletin A300-57-0234, Revision 01, dated March 11, 1998. Thereafter, repeat the inspection at intervals not to exceed 40 flight cycles, until the initial inspections required by paragraph (b) are accomplished.

(b) For all airplanes: Perform a detailed visual and a high frequency eddy current (HFEC) inspection to detect cracks in Gear Rib 5 of the MLG attachment fittings at the lower flange, in accordance with Airbus Service Bulletin A300-57-6087, Revision 01, dated March 11, 1998 (for Model A300-600 series airplanes); or A300-57-0234, Revision 01, dated March 11, 1998 (for Model A300 series airplanes); as applicable; at the time specified in paragraph (b)(1) or (b)(2) of this AD, as applicable. Repeat the inspections thereafter at intervals not to exceed 1,500 flight cycles. Accomplishment of the inspections required by this paragraph terminates the inspections required by paragraph (a) of this AD.

(1) For airplanes that have accumulated 20,000 or more total flight cycles as of March 9, 1998: Inspect within 500 flight cycles after March 9, 1998.

(2) For airplanes that have accumulated less than 20,000 total flight cycles as of March 9, 1998: Inspect prior to the accumulation of 18,000 total flight cycles, or within 1,500 flight cycles after March 9, 1998, whichever occurs later.

NOTE 2: Accomplishment of the initial detailed visual and HFEC inspections in accordance with Airbus Service Bulletin A300-57A0234 or A300-57A6057, both dated August 5, 1997, as applicable, is considered acceptable for compliance with the initial inspections required by paragraph (a) or (b) of this AD.

(c) If any crack is detected during any inspection required by this AD, prior to further flight, repair in accordance with a method approved by the Manager, International Branch, ANM-116, FAA, Transport Airplane Directorate, or the Direction G n rale de l'Aviation Civile (or its delegated agent).

NEW REQUIREMENTS OF THIS AD

Terminating Modification
(d) Prior to the accumulation of 21,000 total flight cycles, or within 2 years after the effective date of this AD, whichever occurs later: Modify Gear Rib 5 of the MLG attachment fittings at the lower flange in accordance with Airbus Service Bulletin A300-57-6088, Revision 01, including Appendix 01 (for Model A300-600 series airplanes), or A300-57-0235, Revision 01, including Appendix 01 (for Model A300 series airplanes), all dated February 1, 1999, as applicable. Accomplishment of this modification constitutes terminating action for the repetitive inspection requirements of this AD.

NOTE 3: Accomplishment of the modification required by paragraph (d) of this AD prior to the effective date of this AD in accordance with Airbus Service Bulletin A300-57-6088 or A300-57-0235, both dated August 5, 1998; as applicable; is acceptable for compliance with the requirements of that paragraph.

Alternative Methods of Compliance
(e) 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, International Branch, ANM-116. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, International Branch, ANM-116.

NOTE 4: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the International Branch, ANM-116.

Special Flight Permits
(f) 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.

Incorporation by Reference
(g) The actions shall be done in accordance with Airbus Service Bulletin A300-57-6087, Revision 01, dated March 11, 1998; Airbus Service Bulletin A300-57-0234, Revision 01, dated March 11, 1998; Airbus Service Bulletin A300-57-6088, Revision 01, dated February 1, 1999, including Appendix 01, dated February 1, 1999; and Airbus Service Bulletin A300-57-0235, Revision 01, dated February 1, 1999, including Appendix 01, dated February 1, 1999; 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 Airbus Industrie, 1 Rond Point Maurice Bellonte, 31707 Blagnac Cedex, France. 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.

NOTE 5: The subject of this AD is addressed in French airworthiness directive 98-151- 247 (B), dated April 8, 1998.

(h) This amendment becomes effective on October 20, 1999.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 98-03-06, amendment 39-10298 (63 FR 5224, February 2, 1998), which is applicable to certain Airbus Model A300 and A300-600 series airplanes, was published in the Federal Register on November 23, 1998 (63 FR 64661). The action proposed to continue to require inspections to detect cracks in Gear Rib 5 of the main landing gear (MLG) attachment fittings at the lower flange, and repair, if necessary. That action also proposed to establish repetitive inspection intervals for certain inspections required by the existing AD. That action also proposed to add a requirement to modify Gear Rib 5 of the MLG attachment fittings, which constitutes terminating action for the repetitive inspections.

Comments Received
Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

Support for the Proposal
One commenter, an operator, expresses no objection to the inspections or modification required by the proposed AD.

Request to Remove Requirement for Terminating Modification
One commenter, the manufacturer, states that, according to the damage-tolerance methodology of design and evaluation, safety is maintained by adequate repetitive inspections because crack initiation and propagation can be anticipated with sufficient precision to allow inspection programs to safely detect and repair metal fatigue or other structural damage before safety is affected (without accomplishing modifications). Therefore, the commenter does not see the need to mandate structural modifications in general, or in the specific case of this proposed AD.

The commenter notes that if inspection results are considered in specific cases to be unreliable due to access difficulty or human factor considerations, the Airworthiness Assurance Working Group (AAWG) of the Aviation Rulemaking Advisory Committee has established three major criteria for determining when a terminating modification should be mandated. The commenter further states that these criteria were developed industry-wide in the context of general aging aircraft activities, but do apply in general to aircraft structures and provide adequate guidance for such a determination. The commenter requests that general guidelines for mandating structural modifications be established in line with the criteria already set forth by the AAWG.

The FAA does not agree that the damage tolerance methodology, and the continuance of long-term repetitive inspections, provide adequate continued operational safety in many cases. Following a structure-related accident in 1988, FAA policy transitioned to a more stringent assessment of whether modifications should be mandated, and worked with the AAWG in development of criteria for such evaluation. The FAA considers this policy necessary to counteract the reduced efficacy of inspection resulting from the increased likelihood of damage as airplanes age.

The FAA agrees that general guidelines should be established that are in line with the criteria set forth by the AAWG. In the case of this AD, the FAA did utilize the AAWG criteria as a general guideline in making the decision to require accomplishment of the modification. The FAA infers that the commenter is requesting that the requirement to accomplish the terminating modification be removed from the proposed AD. The FAA does not concur in this case. In making the determination that the terminating modification should be mandated, several factors were considered, as discussed below.

o Consequence of Failure: As noted by the Direction G n rale de l'Aviation Civile (DGAC), which is the airworthiness authority for France, in its corresponding airworthiness directive, the propagation of cracks in the area of concern could affect the structural integrity of the airplane. Although not stated specifically in the proposed AD, the FAA considers that such reduced integrity could cause permanent deformation of the surrounding structure that could lead to fuel leaks. Further, cracking of Gear Rib 5 of the main landing gear (MLG) attachment fitting could precipitate failure of the fitting, which could possibly lead to failure of the MLG during landing, rupture of the fuel tank, and fire. These factors led the FAA to determine that a significant unsafe condition exists.

o Probability of Occurrence: The referenced Airbus service bulletins document eleven in-service occurrences of cracking, detected on airplanes which had accumulated between 20,959 and 29,023 total flight cycles. The likelihood of cracking therefore appears high for airplanes on which 21,000 total flight cycles or more have been accumulated. Since a number of airplanes exist today in the world with this amount of service, the FAA proposed 21,000 total flight cycles as the compliance time for the modification. Additionally, due to the age of affected airplanes, the FAA considers it possible that other adjacent damage may exist, which could aggravate the seriousness of the cracking.

o Access/Inspection Difficulty: The FAA judges the difficulty of both access to the inspection area and accomplishment of the inspection itself to be above average. Cracks are not evident without a directed inspection, and approximately 3 work hours are required to gain access to the inspection area. Additionally, some cracks found during inspections were already of a substantial length, indicating that such cracking may have existed without detection for some time. Therefore, the FAA concludes that there is a certain level of difficulty in continued access and accomplishment of this inspection.

In consideration of the factors described above, and using the general criteria established by the AAWG, the FAA has determined that accomplishment of the terminating modification is justified.Request to Revise Applicability
One commenter requests that the applicability of the proposed AD be revised to exclude those airplanes on which Airbus Modification 11912 has been installed in production. The commenter notes that this production modification is equivalent to the retrofit solution described in Airbus Service Bulletins A300-57-6088 and A300-57-0235, both dated August 5, 1998, which are referenced in the proposed AD as appropriate terminating action for the repetitive inspection requirements of this AD. The FAA concurs that airplanes on which the production modification or the retrofit modification has been installed may be excluded from the requirements of this AD, and has revised the applicability of the final rule accordingly.

Service Bulletin Revisions
Airbus has issued Service Bulletins A300-57-6088, Revision 01, (for Model A300-600 series airplanes), and A300-57-0235, Revision 01, (for Model A300 series airplanes), both dated February 1, 1999. These revisions clarify work procedures, add Figures, and update the cost and materials information. The FAA has determined that these later revisions of the service bulletins are substantially equivalent to the original issue of the bulletins. Therefore, the FAA has revised paragraph (d) of the final rule to cite Revision 01 of the applicable service bulletins as the appropriate source of service information. A NOTE 3 also has been added to the final rule to provide credit for operators who may have accomplished the modification in accordance with the previously cited service bulletins prior to the effective date of this AD.

Conclusion
After 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 changes previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.

Cost Impact
There are approximately 164 airplanes of U.S. registry that will be affected by this AD.

The inspection currently required by AD 98-03-06, and retained in this new AD, takes approximately 6 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the currently required inspection on U.S. operators is estimated to be $59,040, or $360 per airplane, per inspection cycle.

The modification required by this new AD will take approximately 62 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts will cost approximately $10,270 per airplane. Based on these figures, the cost impact of the new actions required by this AD on U.S. operators is estimated to be $2,294,360, or $13,990 per airplane.

The 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.

Regulatory Impact
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 "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 forthis 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."

List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment
Accordingly, 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:
PART 39 - AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
39.13 [Amended]
2. Section 39.13 is amended by removing amendment 39-10298 (63 FR 5224, February 2, 1998), and by adding a new airworthiness directive (AD), amendment 39-11313, to read as follows: