AD 98-15-04

This amendment adopts a new airworthiness directive (AD), applicable to certain Airbus Model A320 series airplanes, that requires repetitive inspections for fatigue cracking of the bottom flanges of the longitudinal floor beams at frame 43; and repair, if necessary. This amendment also requires a one-time inspection for fatigue cracking of the fastener holes in the longitudinal floor beams, and modification of the floor beams, 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 on the bottom flanges of the longitudinal floor beams, which could result in reduced structural integrity of the airplane.

Final rule.

98-15-04 AIRBUS INDUSTRIE: Amendment 39-10655. Docket 97-NM-197-AD.

Applicability: Model A320 series airplanes, on which Airbus Modification 20904 (reference Airbus Service Bulletin A320-53-1008, dated March 31, 1995) has not 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 (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 include specificproposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To prevent fatigue cracking on the bottom flanges of the longitudinal floor beams at frame 43, which could result in reduced structural integrity of the airplane, accomplish the following:

(a) Prior to the accumulation of 20,000 total flight cycles, or within 1,000 flight cycles after the effective date of this AD, whichever occurs later, perform a visual inspection for fatigue cracking of the longitudinal floor beams at frame 43, in accordance with Airbus Service Bulletin A320-53-1085, dated March 31, 1995.

(1) If no cracking is detected, repeat the visual inspection thereafter at intervals not to exceed 6,000 flight cycles.

(2) If any cracking is detected, prior to further flight, repair in accordance with a method approved by the Manager, International Branch, ANM-116, FAA, Transport Airplane Directorate.

(b) Prior to the accumulation of 32,000 total flight cycles, or within 1,000 flight cycles after the effective date of this AD, whichever occurs later, accomplish paragraphs (b)(1) and (b)(2) of this AD. Accomplishment of paragraphs (b)(1) and (b)(2) constitutes terminating action for the repetitive inspection requirements of this AD.

(1) Perform a one-time eddy current (rotary probe) non-destructive test (NDT) inspection for fatigue cracking of the fastener holes on the longitudinal floor beams at frame 43, in accordance with Airbus Service Bulletin A320-53-1008, dated March 31, 1995. If any cracking is detected, prior to further flight, repair in accordance with a method approved by the Manager, International Branch, ANM-116.

(2) Modify the floor beam fasteners in accordance with Airbus Service Bulletin A320-53-1008, dated March 31, 1995.

(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 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.

(e) The visual inspection shall be done in accordance with Airbus Service Bulletin A320-53-1085, dated March 31, 1995. The eddy current inspection and the modification shall be done in accordance with Airbus Service Bulletin A320-53-1008, dated March 31, 1995. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and1 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 96-236- 089(B), dated October 23, 1996.

(f) This amendment becomes effective on August 19, 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 Model A320 series airplanes was published in the Federal Register on April 14, 1998 (63 FR 18158). That action proposed to require repetitive inspections for fatigue cracking of the bottom flanges of the longitudinal floor beams at frame 43; and repair, if necessary. That action also proposed to require a one-time inspection for fatigue cracking of the fastener holes in the longitudinal floor beams, and modification of the floor beams, which would constitute terminating action for the repetitive inspections.

Comments
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 supports the proposed rule.

Request to Allow Flight With Cracks
One commenter requests that the proposed AD be revised to allow continued operation of the airplane following the detection of cracks, provided operators follow the defined values for follow-on inspections and repairs as recommended in Airbus Service Bulletin A320-53-1085. The commenter states that the structure of Airbus A320 series airplanes is classified as damage tolerant. Additionally, based on fatigue test results and calculations of the crack propagation rate, the manufacturer has defined in the service bulletin an appropriate number of flight cycles for continued flight with cracks, depending on the crack length detected. Finally, the commenter notes that the inspection program recommended in the service bulletin was developed in order to prevent the need for extensive repair of the aircraft.

The FAA does not concur with the commenter s request to allow continued operation of the airplane following the detection of cracks. Generally, the FAA considers that damage tolerance assessment methodologies are effective for establishing an inspection program that will detect cracks before failure occurs, but they are not sufficiently accurate to predict precisely and reliably the rates at which identified cracks will propagate to failure. Additionally, the FAA recognizes that there are adverse human factors associated with the performance of repetitive inspections that may reduce safety if such repair deferrals are practiced routinely.

Therefore, it is FAA policy to require repair of known cracks prior to further flight whether the airplane structure is classified as damage tolerant or not, rather than to use the principles of damage tolerance as a tool to manage existing cracks. There may be certain exceptions to this policy for cases where there is an unusual need for a temporary deferral of the repair, such as difficulty in acquiring parts to accomplish a repair in a timely manner. Since the commenter has not identified any unusual need that would warrant an exception to FAA policy inthis instance, 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.

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 5 airplanes of U.S. registry will be affected by this AD. It will take approximately 3 work hours per airplane to accomplish the required inspection of the bottom flanges, at an average labor rate of $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 $900, or $180 per airplane, per inspection cycle.

It will take approximately 32 work hours per airplane to accomplish the required inspection of the fastener holes and required modification, at an average labor rate of $60 per work hour. Required parts will cost between $649 and $3,056 per airplane, depending on the service kit purchased. Based on these figures, the cost impact of the inspection of the fastener holes and modification required by this AD on U.S. operators is estimated to be as low as $12,845, or $2,569 per airplane, and as high as $24,880, or $4,976 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 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 meby 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: