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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 98-NM-164-AD] 
          - RIN 2120-AA64 

# AGENCY:

Federal Aviation Administration, DOT. 

# ACTION:

Notice of proposed rulemaking (NPRM). 

# SUMMARY:

This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Airbus Model A300-600 series airplanes, that currently requires repetitive ultrasonic inspections to detect cracks in the bolt holes inboard and outboard of rib 9 on the bottom booms of the front and rear wing spars, and repair, if necessary. This action would revise the compliance thresholds for the inspection and would require that the inspections be repeated at reduced intervals. 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 prevent fatigue cracks in the bolt holes of the wing spars, which could result in reduced structural integrity of a wing spar. 

# DATES:

Comments must be received by May 22, 2000. 

# ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 98-NM-164-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                           ( print page 21158)                        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-164-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-164-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. 

## Discussion 

On March 29, 1995, the FAA issued AD 95-07-05, amendment 39-9187 (60 FR 17990, April 10, 1995), applicable to certain Airbus Model A300-600 series airplanes, to require repetitive ultrasonic inspections to detect fatigue cracks in the bolt holes inboard and outboard of rib 9 on the bottom booms of the front and rear wing spars, and repair, if necessary. That action was prompted by the discovery of fatigue cracks that emanated from the bolt holes inboard and outboard of rib 9 in the bottom booms of the front and rear wing spars. The requirements of that AD are intended to prevent cracks in the bolt holes of the wing spars, which could result in reduced structural integrity of a wing spar. 

## Actions Since Issuance of Previous Rule 

                    Since the issuance of that AD, the Direction G                                        en                                        erale de l'Aviation Civile (DGAC), which is the airworthiness authority for France, received a report indicating that, during routine maintenance, a fatigue crack of 3.58 inches (91 millimeters) in length was discovered on the bolt holes of the wing spars on a Model A300 series airplane that had accumulated 29,919 total flight cycles. Investigation revealed that an initial inspection to detect cracks in the bolt holes of the wing spars, in accordance with that AD, had been performed on this airplane at 23,545 total flight cycles. Procedures for this inspection are described in Airbus Service Bulletin A300-57-6039, dated August 1, 1994 (which was referenced in AD 95-07-05 as the appropriate source of service information).                

That service bulletin specified an interval not to exceed 9,000 flight cycles for repetitive inspections, which would have resulted in accomplishment of the next inspection on this airplane at 32,545 total flight cycles. Accomplishment of the next inspection at the scheduled compliance time would have allowed the cracking on this airplane to remain undetected for 2,626 flight cycles. Therefore, the DGAC has concluded that the existing repetitive interval for these inspections does not detect such cracking in a timely manner, and advises that the interval should be reduced. 

## Explanation of Relevant Service Information 

Subsequent to the finding of this new cracking, Airbus issued Service Bulletin A300-57-6037, Revision 1, dated August 31, 1995. The inspection and repair procedures described in Revision 1 of the service bulletin are essentially identical to those described in the original issue of the service bulletin. However, Revision 1 of the service bulletin reduces the repetitive inspection intervals from 9,000 flight cycles, as specified in the original issue of the service bulletin, to 4,800 flight cycles. 

The DGAC classified Revision 1 of this service bulletin as mandatory and issued French airworthiness directive 94-208-169(B)R2, dated October 8, 1997, in order to assure the continued airworthiness of these airplanes in France.

## 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 95-07-05 to continue to require repetitive ultrasonic inspections to detect cracks in the bolt holes inboard and outboard of rib 9 on the bottom booms of the front and rear wing spars, and repair, if necessary. This proposed AD would require that the repetitive inspections be accomplished at a revised threshold and at reduced intervals. The actions would be required to be accomplished in accordance with the service bulletin described previously, except as discussed below. 

## Differences Between Proposed Rule and Service Bulletin 

Operators should note that, unlike particular provisions in the service bulletin regarding adjustment of the compliance times using an “adjustment-for-range” formula, this proposed AD would not permit formulaic adjustments of the inspection compliance times. The FAA has determined that such adjustments may present difficulties in determining if the applicable inspections and modifications have been accomplished within the appropriate time frame. Further, while such adjustable compliance times are utilized as part of the Maintenance Review Board program, they do not fit practically into the AD tracking process for operators or for Principal Maintenance Inspectors attempting to ascertain compliance with AD's. Therefore, the FAA has determined that fixed compliance times should be specified for accomplishment of the actions required by this AD.

Additionally, after discussions with the DGAC and the manufacturer, the FAA has determined that flight-hour maximums should be included as part of the compliance threshold and repetitive intervals for the inspections required by this proposed AD. Inclusion of a compliance threshold in terms of total flight hours as well as total flight cycles, and requiring inspection at the earlier of those times, will ensure that airplanes with longer-than-average flight times are inspected at a threshold and intervals necessary to maintain safety. Accordingly, the FAA has specified that the initial inspection must be accomplished at the earliest time an airplane reaches certain accumulated total flight cycles or total flight hours, and that repetitive inspections are to be accomplished at intervals not to exceed certain flight cycles or flight hours, whichever occurs first.

                    The FAA has determined that such revision of the inspection threshold and                           ( print page 21159)                        reduction of the intervals of the existing AD does not adversely impact any U.S. operators, since no airplanes on the U.S. Register have yet reached those accumulated flight-cycle or flight-hour thresholds.                 

## Cost Impact 

There are approximately 75 airplanes of U.S. registry that would be affected by this proposed AD. 

The inspection that is currently required by AD 95-07-05, and retained in this AD, takes approximately 1 work hour per airplane to accomplish (excluding 10 work hours for access and close-up), at an average labor rate of $60 per work hour. Based on this figure, the cost impact of the currently required inspection on U.S. operators is estimated to be $4,500, or $60 per airplane, per inspection cycle. 

The cost impact figure discussed above is 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.

## 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 amendment 39-9187 (60 FR 17990, April 10, 1995), and by adding a new airworthiness directive (AD), to read as follows: 

**Airbus Industrie:**                                 Docket 98-NM-164-AD. Supersedes AD 95-07-05, Amendment 39-9187.                            

*Applicability:*                                 Model A300-600 series airplanes, certificated in any category, on which Airbus Modification 10161 has not been installed in production.                            

# **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 specific proposed actions to address it.

*Compliance:*                                 Required as indicated, unless accomplished previously.                             

To prevent fatigue cracks in the bolt holes of the wing spars, which could result in reduced structural integrity of a wing spar, accomplish the following:

## Ultrasonic Inspections

(a) Perform an ultrasonic inspection to detect fatigue cracking of the bolt holes inboard and outboard of rib 9 on the bottom booms of the front and rear wing spars, in accordance with Airbus Service Bulletin A300-57-6037, dated August 1, 1994, or Revision 1, dated August 31, 1995, at the applicable time specified in paragraph (a)(1) or (a)(2) of this AD. Repeat the inspection thereafter at intervals not to exceed 4,800 flight cycles or 11,000 flight hours, whichever occurs first.

(1) For airplanes on which Airbus Modification 8842 (reference Airbus Service Bulletin A300-57-6039) has not been installed: Inspect at the earlier of the times specified by paragraphs (a)(1)(i) and (a)(1)(ii) of this AD.

(i) Prior to the accumulation of 17,000 total flight cycles, or within 2,000 flight cycles after May 10, 1995 (the effective date of AD 95-07-05, amendment 39-9187), whichever occurs later. 

(ii) Prior to the accumulation of 39,000 total flight hours. 

(2) For airplanes on which Airbus Modification 8842 has been installed: Inspect at the earlier of the times specified by paragraphs (a)(2)(i) and (a)(2)(ii) of this AD.

(i) Within 17,000 flight cycles after accomplishment of Airbus Modification 8842, or within 2,000 flight cycles after May 10, 1995, whichever occurs later.

(ii) Within 39,000 flight hours after accomplishment of Airbus Modification 8842. 

## Corrective Action 

(b) If any crack is found, prior to further flight, repair in accordance with Airbus Service Bulletin A300-57-6037, dated August 1, 1994, or Revision 1, dated August 31, 1995. Thereafter, perform the repetitive inspections required by paragraph (a) of this AD.

## Alternative Methods of Compliance 

(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, FAA, Transport Airplane Directorate. 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.

## Special Flight Permits 

(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.

# **Note 3:**

The subject of this AD is addressed in French airworthiness directive 94-208-169(B)R2, dated October 8, 1997.

Issued in Renton, Washington, on April 14, 2000. 

Charles D. Huber, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

[FR Doc. 00-9899 Filed 4-19-00; 8:45 am] 

BILLING CODE 4910-13-P