AD 98-18-26

This amendment adopts a new airworthiness directive (AD), applicable to certain Airbus Model A320 series airplanes, that requires repetitive inspections to detect fatigue cracking of the front spar vertical stringers on the wings; and repair, if necessary. This amendment also provides for an optional 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 detect and correct fatigue cracking of the front spar vertical stringers on the wings, which could result in reduced structural integrity of the airframe.

Final rule.

98-18-26 AIRBUS INDUSTRIE: Amendment 39-10742. Docket 98-NM-18-AD.

Applicability: Model A320 series airplanes on which Airbus Modification 21290 (reference Airbus Service Bulletin A320-57-1017, Revision 01, dated March 17, 1997) has not been installed, 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 (c) 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 includespecific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To detect and correct fatigue cracking of the front spar vertical stringers on the wings, which could result in reduced structural integrity of the airframe, accomplish the following:

(a) Prior to the accumulation of 24,000 total flight cycles, or within 60 days after the effective date of this AD, whichever occurs later: Perform an eddy current inspection to detect fatigue cracking of the front spar vertical stringers on the wings, in accordance with Airbus Service Bulletin A320-57-1016, Revision 1, dated December 6, 1995.

(1) If no crack is detected, repeat the eddy current inspection thereafter at intervals not to exceed 14,000 flight cycles.

(2) If any crack is detected, 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 ralede l'Aviation Civile (or its delegated agent). Thereafter, repeat the eddy current inspection at intervals not to exceed 14,000 flight cycles.

(b) Modification of the front spar vertical stringers on the wings, in accordance with Airbus Service Bulletin A320-57-1017, Revision 01, dated March 17, 1997, constitutes terminating action for the repetitive inspection requirements of this AD.

(c) 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 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the International Branch, ANM-116.

(d) Special flight permits may be issued inaccordance 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.

(e) The inspections shall be done in accordance with Airbus Service Bulletin A320-57-1016, Revision 1, dated December 6, 1995, which contains the following list of effective pages:

Page Number
Revision Level Shown on Page
Date Shown on Page
1-4, 7
1
December 6, 1995
5-6, 8-13
Original
September 3, 1991

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 3: The subject of this AD is addressed in French airworthiness directive 97-311-105(B), dated October 22, 1997.

(f) This amendment becomes effective on October 13, 1998.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Airbus A320 series airplanes was published in the Federal Register on May 5, 1998 (63 FR 24760). That action proposed to require repetitive inspections to detect fatigue cracking of the front spar vertical stringers on the wings; and repair, if necessary. That action also proposed to provide for an optional terminating action for the repetitive inspections.

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

Request to Allow Flight with Known Cracks

One commenter, the manufacturer, requests that the proposed AD be revised to allow operators to continue operation of an unrepaired airplane following detection of cracks, utilizing the follow-on inspections and conditions described in Airbus Service Bulletin A320-57-1016, Revision 1, dated December 6, 1995. The commenter states that the follow-on inspection intervals are based on fatigue test results and calculations of the crack propagation rate, depending on the crack length. The commenter also states that the structure of the Airbus Model A320 series airplane is classified as damage tolerant. Additionally, the commenter notes that the inspection program specified in the service bulletin was developed in order to prevent the need for extensive repairs of the aircraft.

The FAA does not concur. It is the FAA's policy to require repair of known cracks prior to further flight, except in certain cases of unusual need, as discussed below. This policy is based on the fact that such damaged airplanes do not conform to the FAA certificated type design, and therefore, are not airworthy until a properly approved repair is incorporated. While recognizing that repair deferrals may be necessary at times, the FAA policy is intended to minimize adverse human factors relating to the lack of reliability of long-term repetitive inspections, which may reduce the safety of the type certificated design if such repair deferrals are practiced routinely.

As noted above, the FAA's policy regarding flight with known cracks does allow deferral of repairs in certain cases, if there is an unusual need for a temporary deferral. Unusual needs include such circumstances as legitimate difficulty in acquiring parts to accomplish repairs. Under such conditions, the FAA may allow a temporary deferral of the repair, subject to a stringent inspection program acceptable to the FAA. The FAA acknowledges that the manufacturer has specified inspection intervals that are intended to allow continued operation with known cracks, and to prevent the need for extensive repairs. However, since the FAA is not aware of any unusual need for repair deferral in regard to this AD, the FAA has not evaluated these inspection intervals.

Additionally, the FAA policy applies to airplanes certificated to damage tolerance evaluation regulations as well as those not so certificated. Therefore, the commenter's statement that "the Airbus Model A320 airplane structure is classified as damage tolerant" is not relevant to the application of the FAA's policy in this regard.

The FAA considers the compliance times in this AD to be adequate to allow operators to acquire parts to have on hand in the event that a crack is detected during inspection. Therefore, the FAA has determined that, due to the safety implications and consequences associated with such cracking, any subject bottom flange or fastener hole that is found to be cracked must be repaired or modified prior to further flight. No change to the final rule is necessary.

Request to Revise Service Bulletin Dates

One commenter supports the intent of the proposed AD, but requests that it be revised to reflect the correct issuance date for Revision 1 ofAirbus Service Bulletins A320-57-1016 and A320-57-1017. The commenter states that the correct issuance date for both of these service bulletins is September 3, 1991. The FAA does not concur. The original version of these service bulletins is dated September 3, 1991, rather than Revision 1. Therefore, the FAA finds that no change to the final rule is necessary.

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 as proposed.

Cost Impact

The FAA estimates that 16 airplanes of U.S. registry will be affected by this AD, that it will take approximately 2 work hours per airplane to accomplish the required inspection, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the inspection required by this AD on U.S. operators is estimated to be $1,920, or $120 per airplane, per inspection cycle.The cost impact figure discussed above is 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.

Should an operator elect to accomplish the optional terminating modification, rather than continue the repetitive inspections, it would require approximately 6 work hours to accomplish it, at an average labor rate of $60 per work hour. Required parts would cost approximately $700 per airplane. Based on these figures, the cost impact of the optional terminating modification provided by this AD on U.S. operators is estimated to be $1,060 per airplane.

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 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."

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 adding the following new airworthiness directive: