AD 96-22142

[Federal Register Volume 61, Number 170 (Friday, August 30, 1996)] [Proposed Rules] [Pages 45910-45912] From the Federal Register Online via the Government Publishing Office [www.gpo.gov] [FR Doc No: 96-22142]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-NM-29-AD] RIN 2120-AA64

Airworthiness Directives; Airbus Model A320 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Airbus Model A320 series airplanes. This proposal would require repetitive inspections to detect wear of the inboard flap trunnions, and modification or replacement, if necessary. This proposal would also require the eventual modification of the trunnions, which would terminate the repetitive inspections. This proposal is prompted by reports of wear damage found on the inboard flap drive trunnions that was caused by chafing of the Teflon rollers of the chain that actuates the sliding panel of the fairing. The actions specified by the proposed AD are intended to prevent such chafing and resultant wear damage, which could result in the failure of the trunnion primary load path; this would adversely affect the fatigue life of the secondary load path and could lead to loss of the flap.

DATES: Comments must be received by October 8, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-103, Attention: Rules Docket No. 96-NM-29-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: Tim Backman, Aerospace Engineer, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206) 227-2797; fax (206) 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 96-NM-29-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-103, Attention: Rules Docket No. 96-NM-29-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The Direction Generale de l'Aviation Civile (DGAC), which is the airworthiness authority for France, recently notified the FAA that an unsafe condition may exist on certain Airbus Model A320 series airplanes. The DGAC advises that several operators have found wear marks on the inboard drive flap trunnions (both left-hand and right- hand) during removal and inspection of the inboard flaps. Investigation has revealed that such wear is caused by chafing of the Teflon rollers of the drive chain that actuates the sliding panel on the track No. 1 fairing. This chafing and resultant wear damage, if not corrected, could result in the failure of the trunnion primary load path. This failure would adversely affect the fatigue life of the secondary load path and, consequently, could lead to the loss of the flap.

Explanation of Relevant Service Information

Airbus has issued Service Bulletin A320-27-1066, dated March 7, 1994; and Revision 1, dated February 21, 1995. These service bulletins describe a program for conducting repetitive inspections to detect wear damage of the inboard flap trunnions. The interval for conducting each inspection depends

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upon the amount of wear detected during the last inspection. These inspections are intended to detect wear marks in the outside diameter (primary load path) of the trunnion before they reach a critical depth that would lead to failure. If wear damage exceeds a certain amount, the service bulletin recommends that the trunnions be modified in accordance with the procedures specified in Airbus Service Bulletin A320-27-1050. Additionally, if wear damage is great (more than 5.0 mm in depth), the service bulletin recommends that Airbus be contacted for further actions. The DGAC classified this service bulletin as mandatory and issued French airworthiness directive (CN) 94-165-055(B), dated July 30, 1994, in order to assure the continued airworthiness of these airplanes in France. Additionally, Airbus has issued Service Bulletin A320-27-1050, Revision 3, dated October 21, 1994, which describes procedures for modifying the inboard flap drive trunnions. The modification is identified as Modification 22881, and entails installing protective half shells on the trunnion assembly to prevent chafing and wear damage. Once this modification is accomplished, the repetitive inspections of the trunnions to detect wear marks are no longer necessary. The DGAC has approved the technical content of this service bulletin and has classified it as ``recommended.''

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 the 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 require repetitive inspections to detect wear of each inboard flap trunnion. It would also require that the trunnion be either modified or replaced, depending upon the amount of wear detected. This proposed AD also would require that Modification 22881 be installed eventually on trunnions of all affected airplanes as terminating action for the repetitive inspections. The inspection, modification, and replacement actions would be required to be accomplished in accordance with the service bulletins described previously.

Differences Between Proposed Rule and Service Information

The inboard flap attachment trunnion is a primary structural element that is designed with both a primary and a secondary load path. The wear marks that have been found have been located on the outside diameter of the trunnion, which is the primary load path. Modification 22881, described in Airbus Service Bulletin A320-27-1050, entails installing protective half-shells on this outside diameter to prevent further wear damage. Unlike the Airbus service bulletin and the French CN, this proposed AD would require the installation of Modification 22881as terminating action for the repetitive inspections. The FAA has determined that long term continued operational safety will be better assured by modifications or design changes to remove the source of the problem, rather than by repetitive inspections. Long term inspections may not be providing the degree of safety assurance necessary for the transport airplane fleet. This, coupled with a better understanding of the human factors associated with numerous repetitive inspections, has led the FAA to consider placing less emphasis on special procedures and more emphasis on design improvements. The proposed modification requirement is in consonance with these considerations.

Cost Impact

The FAA estimates that 91 airplanes of U.S. registry would be affected by this proposed AD. Accomplishment of the proposed inspections would take approximately 3 work hours per airplane, at an average labor rate of $60 per work hour. (This includes the time necessary to gain access, inspect, and close up.) Based on these figures, the cost impact of the proposed inspection requirement on U.S. operators is estimated to be $16,380, or $180 per airplane, per inspection. Accomplishment of the proposed modification would require approximately 93 work hours, at an average labor rate of $60 per work hour. (This includes the time necessary to gain access, modify, test, and close up.) Required parts would cost approximately $1,923 per airplane. Based on these figures, the cost impact of the proposed modification requirement on U.S. operators is estimated to be $682,773, or $7,502 per airplane. The cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the 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 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 proposal would not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. 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), 40101, 40113, 44701.

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Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new airworthiness directive:

Airbus: Docket 96-NM-29-AD.

Applicability: Model A320-111, -211, -212, -231, and -232 series airplanes; as listed in Airbus Service Bulletin A320-27-1066, Revision 1, dated February 21, 1995; and on which Airbus Modification 22881 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 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 chafing and resultant wear damage to the inboard flap trunnion, which could result in the failure of the trunnion primary load path, could adversely affect the fatigue life of the secondary load path, and could lead to loss of the flap, accomplish the following: (a) Prior to the accumulation of 500 flight hours after the effective date of this AD, conduct a detailed visual inspection to detect wear marks on each inboard flap trunnion (right-hand and left-hand), in accordance with Airbus Service Bulletin A320-27-1066, dated March 7, 1994, or Revision 1, dated February 21, 1995. Measure and record the depth of all wear marks found on each trunnion, in accordance with the service bulletin. (1) If no wear marks are found or if the depth of the deepest wear mark is less than or equal to 2.0 mm: Repeat the inspection at intervals not to exceed 5,000 flight hours. (2) If the depth of the deepest wear mark is greater 2.0 mm but less than or equal to 3.0 mm: Repeat the inspection within the next 1,000 flight hours. Prior to the accumulation of 5,000 flight hours after the initial inspection, modify the trunnion (Modification 22881) in accordance with Airbus Service Bulletin A320-27-1050, Revision 3, dated October 21, 1994. This modification constitutes terminating action for the repetitive inspections of that trunnion required by this AD. (3) If the depth of the deepest wear mark is greater 3.0 mm, but is less than or equal to 4.0 mm: Prior to the accumulation of 500 flight hours after the initial inspection, modify the trunnion (Modification 22881) in accordance with Airbus Service Bulletin A320-27-1050, Revision 3, dated October 21, 1994. This modification constitutes terminating action for the repetitive inspections of that trunnion that are required by this AD. (4) If the deepest wear mark exceeds 4.0 mm: Prior to further flight, replace the trunnion in accordance with the Airbus Model A320 Maintenance Manual. This replacement constitutes terminating action for the repetitive inspections of that trunnion that are required by this AD. (b) Prior to the accumulation of 10,000 total flight hours, modify each inboard flap trunnion, right-hand and left-hand, (Modification 22881) in accordance with Airbus Service Bulletin A320-27-1050, Revision 3, dated October 21, 1994. Accomplishment of this modification on each trunnion constitutes terminating action for the inspections required by 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, Standardization Branch, ANM-113. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Standardization Branch, ANM-113.

Note 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Standardization Branch, ANM-113.

(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.

Issued in Renton, Washington, on August 23, 1996. Darrell M. Pederson, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 96-22142 Filed 8-29-96; 8:45 am] BILLING CODE 4910-13-P