# AGENCY:

Federal Aviation Administration, DOT. 

# ACTION:

Notice of proposed rulemaking (NPRM). 

# SUMMARY:

This document proposes the supersedure of two existing airworthiness directives (AD), applicable to certain Airbus Model A320 series airplanes, that currently require modification of the rear spar web of the wing and cold expansion of certain attachment holes for the forward pintle fitting and certain holes at the actuating cylinder anchorage of the main landing gear (MLG). This proposed action would add a requirement for repetitive inspections to detect fatigue cracking in certain areas of the rear spar of the wing, and corrective action, if necessary. This proposed action would also provide for optional terminating action for the requirements of this AD. This proposal is prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by the proposed AD are intended to detect and correct fatigue cracking, which may lead to reduced structural integrity of the wing and the MLG. 

# DATES:

Comments must be received by March 13, 2000. 

# ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 98-NM-99-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal holidays. 

The service information referenced in the proposed rule may be obtained from Airbus Industrie, 1 Rond Point Maurice Bellonte, 31707 Blagnac Cedex, France. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington. 

# FOR FURTHER INFORMATION CONTACT:

Norman B. Martenson, Manager, International Branch, ANM-116, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2110; fax (425) 227-1149. 

# SUPPLEMENTARY INFORMATION: 

## Comments Invited 

Interested persons are invited to participate in the making of the proposed rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this notice may be changed in light of the comments received. 

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report summarizing each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket. 

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this notice must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 98-NM-99-AD.” The postcard will be date stamped and returned to the commenter. 

## Availability of NPRMs 

Any person may obtain a copy of this NPRM by submitting a request to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 98-NM-99-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. 

## Discussion 

On April 26, 1993, the FAA issued AD 93-08-15, amendment 39-8563 (58 FR 27923, May 12, 1993), applicable to certain Airbus Model A320 series airplanes, which requires modification of the rear spar web of the wing. 

On December 21, 1993, the FAA issued AD 93-25-13, amendment 39-8777 (59 FR 1903, January 13, 1994), applicable to certain Airbus Model A320 series airplanes, which requires cold expansion of certain attachment holes for the forward pintle fitting and certain holes at the actuating cylinder anchorage of the main landing gear (MLG). 

Those actions were prompted by the results of fatigue testing conducted by the manufacturer. The requirements of those ADs are intended to prevent fatigue cracking, which may lead to reduced structural integrity of the wing and MLG. 

## Actions Since Issuance of Previous Rules 

                    Since the issuance of AD 93-08-13 and AD 93-25-13, the Direction Ge                                        ne                                        rale de l'Aviation Civile (DGAC), which is the airworthiness autority for France, has advised the FAA that cracks were found on a Model A320 series airplane despite compliance with the requirements of those ADs. Investigation by the manufacturer provided further indication that an airplane on which the modifications required by that AD were installed could experience cracking prior to reaching the design life limits of the airplane. In response to these findings, the DGAC mandated repetitive ultrasonic inspections to detect fatigue cracks on the rear spar to ensure the structural integrity of the airplane.                 

Subsequent analysis of the results of the ultrasonic inspections indicated that reducing the inspection threshold for selected holes would ensure the structural integrity of the area and prevent the need for extensive repairs of the wing inner rear spar. 

## Explanation of Relevant Service Information 

Airbus issued Service Bulletin A320-57-1088, dated September 30, 1996; Revision 01, dated September 17, 1997; and Revision 02, dated July 29, 1999. This service bulletin describes procedures for repetitive ultrasonic inspections to detect cracking of the rear spar of the wing in the area of holes for the attachment of the gear rib, the forward pintle fitting, and the MLG actuating cylinder anchorage. Revision 02 specifies a reduced threshold for the initial inspection of certain holes [holes 52 through 55 (actuating cylinder anchorage) and holes 82, 83, 87, and 88 (gear support rib)]; the compliance time for the initial inspection of the remaining 32 holes is unchanged. 

Accomplishment of the actions specified in the service bulletin described previously is intended to adequately address the identified unsafe condition. The DGAC classified Airbus Service Bulletin A320-57-1088 as mandatory and issued French airworthiness directive 1999-264-135(B), dated June 30, 1999, in order to ensure the continued airworthiness of these airplanes in France. 

                    Airbus also issued Service Bulletin A320-57-1089, dated December 22, 1996, Revision 01, dated April 17, 1997; and Revision 02, dated November 6, 1998. This service bulletin describes a modification of all affected fastener holes in the rear spar of the wing. The modification involves a cold re-expansion of the holes in the rear spar of the wing for the attachment of gear rib 5, the forward pintle fitting, and the actuating cylinder anchorage; cold expansion of the pintle fitting and gear rib 5; and installation of interference fit fasteners into the rear spar and gear rib 5 while maintaining a clearance fit in the actuating cylinder anchorage and pintle fitting. This service bulletin specifies that the modification would                     Start Printed Page 6568                    eliminate the need for the repetitive ultrasonic inspections specified by Airbus Service Bulletin A320-57-1088. It would also eliminate the need for the modification specified by Airbus Service Bulletin A320-57-1004 and the cold expansion specified by Airbus Service Bulletin A320-57-1060, if accomplished prior to the accumulation of 12,000 total flight cycles.                 

## FAA's Conclusions 

This airplane model is manufactured in France and is type certificated for operation in the United States under the provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, the DGAC has kept the FAA informed of the situation described above. The FAA has examined the findings of the DGAC, reviewed all available information, and determined that AD action is necessary for products of this type design that are certificated for operation in the United States. 

## Explanation of Requirements of Proposed Rule 

Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design registered in the United States, the proposed AD would supersede AD 93-08-15 and AD 93-25-13 to continue to require modification of the wing rear spar web and cold expansion of certain attachment holes for the forward pintle fitting and certain holes at the actuating cylinder anchorage of the MLG. The proposed AD would add a requirement for repetitive ultrasonic inspections to detect fatigue cracking in certain areas of the wing rear spar, and repair of cracking. This proposed AD also would provide for optional terminating action for the inspections proposed by this AD. 

## Difference Between Proposed Rule and Service Bulletin 

Operators should note that, although Service Bulletin A320-57-1088 specifies that the manufacturer may be contacted for a repair if cracks are found, this proposal would require the repair of those cracks to be accomplished in accordance with a method approved by the FAA or the DGAC (or its delegated agent). In light of the type of repair that would be required to address the identified unsafe condition, and in consonance with existing bilateral airworthiness agreements, the FAA has determined that, for this proposed AD, a repair approved by the FAA or the DGAC would be acceptable for compliance with this proposed AD. 

## Cost Impact 

There are approximately 126 airplanes of U.S. registry that would be affected by this proposed AD. 

Subsequent to the issuance of AD 93-08-15 and AD 93-25-13, the FAA reviewed the figure it used in calculating the labor rate relevant to the required AD activities. In order to account for various inflationary costs in the airline industry, the FAA has found it appropriate to increase the labor rate used in these calculations from $55 per work hour to $60 per work hour. The economic impact information, below, has been revised to reflect this increase in the specified hourly labor rate. 

It takes approximately 60 work hours per airplane to accomplish the modification of the rear spar web of the wing, as required by AD 93-08-15 and retained in this AD, at an average labor rate of $60 per work hour. Based on these figures, the total cost impact of the modification on U.S. operators is estimated to be $3,600 per airplane. 

It takes approximately 600 work hours per airplane to accomplish the cold expansion of certain holes associated with the MLG, as required by AD 93-25-13 and retained in this AD, at an average labor rate of $60 per work hour. Required parts are provided by the manufacturer at no cost to the operators. Based on these figures, the total cost impact of the cold expansion on U.S. operators is estimated to be $36,000 per airplane. 

The inspection that is proposed in this AD action would take approximately 24 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 inspection proposed by this AD on U.S. operators is estimated to be $181,440, or $1,440 per airplane, per inspection cycle. 

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the current or proposed 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 action specified in this proposed AD, it would take approximately 750 work hours, at an average labor rate of $60 per work hour. The required parts would cost $27,036; $30,595; or $32,727; depending on the airplane configuration. Based on these figures, the cost per airplane of the optional terminating action proposed by this AD is estimated to be $72,036; $75,595; or $77,727. 

## Regulatory Impact 

The regulations proposed herein would not have a substantial direct effect 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, it is determined that this proposal would not have federalism implications under Executive Order 13132. 

                    For the reasons discussed above, I certify that this proposed regulation (1) is not a “significant regulatory action” under Executive Order 12866; (2) is not a “significant rule” under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) if promulgated, 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 copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption                     **ADDRESSES.**

# List of Subjects in 14 CFR Part 39

- Air transportation
- Aircraft
- Aviation safety
- Safety

## The Proposed Amendment 

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend 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

2. Section 39.13 is amended by removing amendments 39-8563 (58 FR 27923, May 12, 1993) and 39-8777 (59 FR 1903, January 13, 1994) and by adding a new airworthiness directive (AD), to read as follows:

**Airbus Industrie:**                                 Docket 98-NM-99-AD. Supersedes AD 93-08-15, Amendment 39-8563; and AD 93-25-13, Amendment 39-8777.                             

*Applicability:*                                 Model A320 series airplanes, certificated in any category, except those on which Airbus Modification 24591 (Airbus Service Bulletin A320-57-1089, dated December 22, 1996; Revision 01, dated April 17, 1997; or Revision 02, dated November 6, 1998) has been accomplished.                             
Start Printed Page 6569

# 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 (f)(1) 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 detect and correct fatigue cracking in certain areas of the rear spar of the wing, which may lead to reduced structural integrity of the wing and the main landing gear (MLG), accomplish the following: 

## Restatement of Actions Required by AD 93-08-15 

(a) For airplanes having manufacturer's serial numbers (MSN) 003 through 008 inclusive, and 010 through 021 inclusive: Prior to the accumulation of 12,000 total flight cycles, or within 500 flight cycles after June 11, 1993 (the effective date of AD 93-08-15, amendment 39-8563), whichever occurs later, modify the inner rear spar web of the wing in accordance with Airbus Industrie Service Bulletin A320-57-1004, Revision 01, dated September 24, 1992, or Revision 02, dated June 14, 1993. 

## Restatement of Actions Required by AD 93-25-13 

(b) For airplanes having MSN's 002 through 051 inclusive: Prior to the accumulation of 12,000 total flight cycles, or within 2,000 flight cycles after February 14, 1994 (the effective date of AD 93-25-13, amendment 39-8777), whichever occurs later, accomplish the requirements of paragraphs (b)(1) and (b)(2) of this AD in accordance with Airbus Industrie Service Bulletin A320-57-1060, dated December 8, 1992; or Revision 02, dated December 16, 1994. 

(1) Perform a cold expansion of all the attachment holes for the forward pintle fitting of the MLG, except for the holes that are for taper-lok bolts. 

(2) Perform a cold expansion of the holes at the actuating cylinder anchorage of the MLG. 

# Note 2:

Accomplishment of the cold expansion in accordance with Airbus Service Bulletin A320-57-1060, Revision 01, dated April 26, 1993, is also acceptable for compliance with the requirements of paragraph (b) of this AD.

## New Actions Required by This AD

(c) For all airplanes: Perform an ultrasonic inspection to detect cracking of the rear spar of the wing, in accordance with Airbus Service Bulletin A320-57-1088, Revision 02, dated July 29, 1999; at the applicable time specified by paragraph (c)(1) or (c)(2) of this AD. Repeat the inspection thereafter at intervals not to exceed 3,600 flight cycles. 

(1) For airplanes on which the actions specified by Airbus Service Bulletin A320-57-1004, Revision 02, dated June 14, 1993, or earlier version; and Airbus Service Bulletin A320-57-1060, Revision 02, dated December 16, 1994, or earlier version; have been accomplished: Perform the inspection of all applicable fastener holes within 12,000 flight cycles after accomplishment of the service bulletins, or within 750 flight cycles after the effective date of this AD, whichever occurs later. 

(2) For airplanes on which the actions specified by Airbus Modification 20740 and Airbus Service Bulletin A320-57-1060, Revision 02, dated December 16, 1994, or earlier version, have been accomplished; or on which Airbus Modifications 20740, 20741, and 20796 have been accomplished: Perform the inspections at the locations and applicable times specified by paragraphs (c)(2)(i) and (c)(2)(ii) of this AD. 

(i) Perform the inspection of left and right fastener holes 52 to 55, 82, 83, 87, and 88; located in the rear spar of the wing; prior to the accumulation of 17,300 total flight cycles, or within 750 flight cycles after the effective date of this AD, whichever occurs later. If any cracking is found, prior to further flight, accomplish the requirements of paragraph (c)(2)(ii) of this AD. 

(ii) Except as required by paragraph (c)(2)(i) of this AD: Perform the inspection of all fastener holes located in the rear spar of the wing that are not identified in paragraph (c)(2)(i) of this AD prior to the accumulation of 20,000 total flight cycles, or within 200 flight cycles after the effective date of this AD, whichever occurs later. 

# Note 3:

Accomplishment of the actions specified by Airbus Service Bulletin A320-57-1088, dated September 30, 1996, or Revision 01, dated September 17, 1997, prior to the effective date of this AD is acceptable for compliance with the requirements of the initial inspection required by paragraph (c) of this AD.

(d) If any crack is found during any inspection required by paragraph (c) of this AD: Prior to further flight, repair in accordance with a method approved by either the Manager, International Branch, ANM-116, FAA, Transport Airplane Directorate; or the DGAC (or its delegated agent). For a repair method to be approved by the Manager, International Branch, ANM-116, as required by this paragraph, the Manager's approval letter must specifically reference this AD. 

## Optional Terminating Action 

(e) Modification of all specified fastener holes in the rear spar of the wing in accordance with Airbus Service Bulletin A320-57-1089, dated December 22, 1996; Revision 01, dated April 17, 1997; or Revision 02, dated November 6, 1998; constitutes terminating action for the ultrasonic inspections required by this AD. Such modification, if accomplished prior to the accumulation of 12,000 total flight cycles, constitutes terminating action for the actions required by paragraphs (a) and (b) of this AD. 

## Alternative Methods of Compliance 

(f)(1) 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. 

(2) Alternative methods of compliance, approved previously in accordance with AD 93-25-13; amendment 39-8777, are approved as alternative methods of compliance with this AD. 

# 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 

(g) 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. 

# Note 5:

The subject of this AD is addressed in French airworthiness directive 1999-264-135(B), dated June 30, 1999.

Issued in Renton, Washington, on February 4, 2000. 

Donald L. Riggin, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 00-3132 Filed 2-9-00; 8:45 am] 

BILLING CODE 4910-13-U