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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 99-NM-355-AD] 
          - RIN 2120-AA64 

# AGENCY:

Federal Aviation Administration, DOT. 

# ACTION:

Notice of proposed rulemaking (NPRM). 

# SUMMARY:

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all British Aerospace Model BAe 146 and certain Model Avro 146-RJ series airplanes. This proposal would require inspections and torque checks of the stringer crown fittings and bolts at Ribs 0 and 2 of the wings for discrepancies, corrective action, if necessary; and eventual modification of the stringer crown fittings, which would terminate the inspections and checks. This action is necessary to prevent increased loads on the upper wing skin due to looseness of the stringer fittings and bolts at Ribs 0 and 2 of the wings, which could result in reduced structural integrity of the wings. This action is intended to address the identified unsafe condition. 

# DATES:

Comments must be received by July 28, 2000. 

# ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-355-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. Comments may also be sent via the Internet using the following address: 9-anm-nprmcomment@faa.gov. Comments sent via the Internet must contain “Docket No. 99-NM-355-AD” in the subject line and need not be submitted in triplicate. Comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 for Windows or ASCII text. 

The service information referenced in the proposed rule may be obtained from British Aerospace Regional Aircraft American Support, 13850 Mclearen Road, Herndon, Virginia 20171. 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. 

Submit comments using the following format: 
    - Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.
    - For each issue, state what specific change to the proposed AD is being requested.
    - Include justification (e.g., reasons or data) for each request.

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 99-NM-355-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. 99-NM-355-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. 

## Discussion 

The Civil Aviation Authority (CAA), which is the airworthiness authority for the United Kingdom, notified the FAA that an unsafe condition may exist on all British Aerospace Model BAe 146 and certain Model Avro 146-RJ series airplanes. The CAA advises that, during in-service maintenance inspections inside the upper part of the center and outer wing fuel tanks at Ribs 0 and 2, loose Jo-bolts and movement at the stringer crown fittings have been found. Movement in this area will cause increased loads on the upper wing skin. This condition, if not corrected, could result in reduced structural integrity of the wings. 

## Explanation of Relevant Service Information 

                    British Aerospace has issued Service Bulletin SB.57-56, dated September 2, 1999, which describes procedures for repetitive detailed visual inspections of the stringers and torque checks of the Jo-bolts at Ribs 0 and 2 of the wings for discrepancies. The discrepancies include loose Jo-bolts, loose stringer crown fittings, fretting of fittings and stringers, and cracking or other damage of attachments to the upper skin and joint plates. The service bulletin also describes procedures for modification of all stringer crown fittings at Ribs 0 and 2 of the wings, which would eliminate the need for the repetitive inspections. The modification includes detailed visual and eddy current inspections for discrepancies (                    *i.e.*, fretting, cracking, corrosion) of the stringers, fittings, and upper wing skin; repairs, if necessary; and installation of oversize interference fit radial-lock fasteners per Repair Instruction (R.I.L. HC571H9033).                 

Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition. The CAA classified this service bulletin as mandatory and issued British airworthiness directive 004-09-99 in order to assure the continued airworthiness of these airplanes in the United Kingdom. 

## FAA's Conclusions 

                    These airplane models are manufactured in the United Kingdom and are type certificated for operation in the United States under the provisions                           ( print page 39832)                        of § 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, the CAA has kept the FAA informed of the situation described above. The FAA has examined the findings of the CAA, 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 require accomplishment of the actions specified in the service bulletin described previously, except as discussed below. 

## Differences Between Proposed Rule and the Service Bulletin 

Operators should note that, although the service bulletin specifies that the manufacturer may be contacted for disposition of certain repair conditions, this proposal would require the repair of those conditions to be accomplished in accordance with a method approved by either the FAA or the CAA (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 either the FAA or the CAA would be acceptable for compliance with this proposed AD. 

## Cost Impact 

The FAA estimates that 20 airplanes of U.S. registry would be affected by this proposed AD. 

It would take approximately 8 work hours per airplane to accomplish the proposed inspection, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed inspection on U.S. operators is estimated to be $9,600, or $480 per airplane, per inspection cycle. 

It would take approximately 450 work hours per airplane (including access and close) to accomplish the proposed modification, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed modification on U.S. operators is estimated to be $540,000, or $27,000 per airplane. 

The cost impact figures discussed above are 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 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 adding the following new airworthiness directive: 

**British Aerospace Regional Aircraft**

(Formerly British Aerospace Regional Aircraft Limited, Avro International Aerospace Division; British Aerospace, PLC; British Aerospace Commercial Aircraft Limited): Docket 99-NM-355-AD. 

*Applicability:*                                 All Model BAe 146 series airplanes; and Model Avro 146-RJ series airplanes, as listed in British Aerospace Service Bulletin SB.57-56, dated September 2, 1999; certificated in any category; except those on which British Aerospace Modification HCM01307A or HCM01307B [Reference Repair Instruction (R.I.L. HC571H9033)] has been accomplished.                             

# 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 increased loads on the upper wing skin due to looseness of the stringer fittings and bolts at Ribs 0 and 2 of the wings, which could result in reduced structural integrity of the wings, accomplish the following: 

## Inspections and Modification 

(a) Prior to the accumulation of 14,000 total flight cycles, or within 4,000 flight cycles after the effective date of this AD, whichever occurs later: Perform a detailed visual inspection of the stringers and a torque check of the Jo-bolts at Ribs 0 and 2 of the wings for discrepancies (including loose Jo-bolts and stringer crown fittings, fretting of fittings and stringers, and cracking or damage of attachments); in accordance with British Aerospace Service Bulletin SB.57-56, dated September 2, 1999. 

(1) If no discrepancy is found, or, if 1, 2, or 3 loose Jo-bolts are found per rib side and no loose crown (dagger) fittings are found (Category 1 or 2, as specified in Table 2 of paragraph D. “Compliance” of the service bulletin), accomplish the actions required in paragraphs (a)(1)(i) and (a)(1)(ii) of this AD. 

(i) Repeat the inspection thereafter at the applicable times specified in Table 2, until accomplishment of the actions required by paragraph (a)(1)(ii). 

(ii) Prior to accumulation of 40,000 total flight cycles, or within 4,000 flight cycles after the effective date of this AD, whichever occurs later: Modify all stringer crown fittings at Ribs 0 and 2 of the wings (including inspections, repairs, and installation of oversize interference fit fasteners per R.I.L. HC571H9033) in accordance with the service bulletin, except as required by paragraph (b) of this AD. This modification terminates the requirements of this AD. 

                                (2) If any other discrepancy is found, as specified in Table 2 (Categories 3 through 6): At the applicable times specified in Table 2, repeat the inspection thereafter, and modify all crown fittings at Ribs 0 and 2 of the wings (including inspections, repairs, and installation of oversize interference fit fasteners per R.I.L. HC571H9033); in accordance with the service bulletin, except as required by paragraph (b) of this AD. This                                       ( print page 39833)                                    modification terminates the requirements of this AD.                             

# Note 2:

For the purposes of this AD, a detailed visual inspection is defined as: “An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required.” 

## Approved Repairs 

(b) Where British Aerospace Service Bulletin SB.57-56, dated September 2, 1999, specifies to contact the manufacturer for a repair, 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 Civil Aviation Authority of the United Kingdom (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. 

## 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. 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 3:

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 §§ 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 4:

The subject of this AD is addressed in British airworthiness directive 004-09-99.

Issued in Renton, Washington, on June 22, 2000. 

Donald L. Riggin, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 00-16359 Filed 6-27-00; 8:45 am] 

BILLING CODE 4910-13-U