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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 2000-NM-157-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 certain Boeing Model 767 series airplanes powered by General Electric or Pratt & Whitney engines. This proposal would require repetitive inspections to detect discrepancies of the aft-most fastener holes in the horizontal tangs of the midspar fitting of the strut, and corrective actions, if necessary. This proposal also provides for optional terminating action for the repetitive inspections. This action is necessary to prevent fatigue cracking in primary strut structure and reduced structural integrity of the strut, which could result in separation of the strut and engine. This action is intended to address the identified unsafe condition. 

# DATES:

Comments must be received by November 24, 2000. 

# ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-157-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 be submitted via fax to (425) 227-1232. Comments may also be sent via the Internet using the following address: 9-anm-nprmcomment@faa.gov. Comments sent via fax or the Internet must contain “Docket No. 2000-NM-157-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 Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington. 

# FOR FURTHER INFORMATION CONTACT:

James Rehrl, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2783; fax (425) 227-1181. 

# 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 2000-NM-157-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. 2000-NM-157-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.                           ( print page 60125)    

## Discussion 

The FAA has received a report indicating fatigue cracking of an inboard midspar fitting on the number two pylon of a Boeing Model 767 series airplane powered by General Electric engines. The crack was detected during replacement of a midspar fitting bushing, and the airplane had accumulated 21,375 total flight hours and 11,563 total flight cycles. A cracked midspar fitting could result in a fractured fitting and drooping of the strut at the strut-to-wing interface. Structural assessment indicates that the actual operational loads applied to the nacelle strut and wing structure are higher than the analytical loads that were used during the initial design. Subsequent analysis and service history, which includes numerous reports of fatigue cracking on certain strut and wing structure, indicate that fatigue cracking can occur on the primary strut structure before an airplane reaches its design service objective of 20 years or 50,000 total flight cycles. Analysis also indicates that such cracking, if it were to occur, would grow at a much greater rate than originally expected. This condition, if not corrected, could result in reduced structural integrity of the strut and separation of the strut and engine. 

## Explanation of Relevant Service Information 

The FAA has reviewed and approved Boeing Service Bulletin 767-54A0101, Revision 1, dated February 3, 2000, which describes procedures for accomplishment of either repetitive detailed visual or high frequency eddy current inspections to detect discrepancies (cracking, incorrect fastener hole diameter), of the aft-most fastener holes in the horizontal tangs of the midspar fitting of the strut, and corrective actions. The corrective actions consist of rework of the aft-most fastener holes or replacement of the midspar fittings of the strut. The service bulletin references the strut improvement program (SIP) for accomplishment of the replacement. The service bulletin also specifies contacting the manufacturer for accomplishment of certain repairs. Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition. 

## Explanation of Requirements of Proposed Rule 

Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, 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 Service Bulletin 

Operators should note that, although the service bulletin describes procedures for inspections of the two aft-most fastener holes of the midspar fitting to detect cracking, this proposed AD would require inspections of the four aft-most fastener holes of the midspar fitting. The FAA has determined that this is necessary due to the service history of cracking on the Model 747 series airplane midspar fittings, which are made of the same material as the midspar fittings on the Model 767 series airplane and are also subject to similar loading conditions. 

Operators also should note that, although the service bulletin specifies that the manufacturer may be contacted for disposition of certain repair conditions; this proposed AD would require the repair of those conditions to be accomplished in accordance with a method approved by the FAA, or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make such findings. 

This proposed AD also would allow operators the option, if cracking is detected, of either repair of the midspar fitting or replacement with a serviceable fitting in accordance with a method approved by the FAA. This is due to the fact that parts are not always readily available and operators required to accomplish the strut improvement program before further flight could have a problem obtaining these parts. 

## Cost Impact 

There are approximately 636 Model 767 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 235 airplanes of U.S. registry would be affected by this proposed AD. 

It would take approximately 1 work hour per airplane to accomplish the proposed detailed visual 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 $14,100, or $60 per airplane, per inspection cycle. 

It would take approximately 3 work hours per airplane to accomplish the proposed eddy current 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 $42,300, or $180 per airplane, per inspection cycle. 

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 proposed AD were not adopted. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions. 

## 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. 

      ( print page 60126)    
§ 39.13 

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

**Boeing:**                                 Docket 2000-NM-157-AD.                             

*Applicability:*                                 Model 767 series airplanes, certificated in any category, as listed in Boeing Service Bulletin 767-54A0101, Revision 1, dated February 3, 2000.                             

# 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 (d) 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 cracking in primary strut structure and reduced structural integrity of the strut, which could result in separation of the strut and engine, accomplish the following: 

## Repetitive Inspections/Corrective Actions 

(a) Before the accumulation of 10,000 total flight cycles, or within 600 flight cycles after the effective date of this AD, whichever occurs later: Accomplish the inspections required by paragraph (a)(1) or (a)(2) of this AD, as applicable. 

(1) Perform a detailed visual inspection of the four aft-most fastener holes in the horizontal tangs of the midspar fitting of the strut to detect cracking, in accordance with Part 1, “Detailed Visual Inspection,” of the Accomplishment Instructions of Boeing Service Bulletin 767-54A0101, Revision 1, dated February 3, 2000. If no cracking is detected, repeat the inspection thereafter at the applicable intervals specified in Table 1, “Reinspection Intervals for Part 1—Detailed Visual Inspection” included in Figure 1 of the service bulletin. 

# 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.” 

(2) Perform a high frequency eddy current inspection of the four aft-most fastener holes in the horizontal tangs of the midspar fitting of the strut to detect discrepancies (cracking, incorrect fastener hole diameter), in accordance with Part 2, “High Frequency Eddy Current (HFEC) Inspection,” of the Accomplishment Instructions of the service bulletin. Accomplish the requirements specified in paragraph (a)(2)(i) or (a)(2)(ii) of this AD, as applicable; and repeat the inspection thereafter at the applicable intervals specified in Table 2, “Reinspection Intervals for Part 2—HFEC Inspection” included in Figure 1 of the service bulletin. 

(i) If no cracking is detected and the fastener hole diameter is less than or equal to 0.5322 inch, rework the hole in accordance with Part 3 of the Accomplishment Instructions of the service bulletin. 

(ii) If no cracking is detected and the fastener hole diameter is greater than 0.5322 inch, accomplish the requirements specified in either paragraph (b)(1) or (b)(2) of this AD. 

(b) If any cracking is detected after accomplishment of any inspection required by paragraph (a) of this AD, before further flight, accomplish the requirements specified in either paragraph (b)(1) or (b)(2) of this AD. 

(1) Accomplish the terminating action specified in Part 4 of the Accomplishment Instructions of Boeing Service Bulletin 767-54A0101, Revision 1, dated February 3, 2000. Accomplishment of this paragraph terminates the requirements of this AD. 

(2) Replace the midspar fitting of the strut with a serviceable part, or repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA. Repeat the applicable inspection thereafter at the applicable time specified in paragraph (a)(1) or (a)(2) of this AD. 

(c) If any discrepancies (cracking, incorrect fastener hole diameter) are detected after accomplishment of any inspection required by paragraph (a) of this AD, for which the service bulletin specifies that the manufacturer may be contacted for disposition of those repair conditions: Before further flight, accomplish the corrective actions (including fastener hole rework and/or midspar fitting replacement) in accordance with a method approved by the Manager, Seattle ACO; or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the Manager, Seattle ACO, to make such findings. 

## Alternative Methods of Compliance 

(d) 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, Seattle ACO. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO. 

# Note 3:

Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.

## Special Flight Permit 

(e) 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 October 3, 2000. 

Donald L. Riggin, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 00-25968 Filed 10-6-00; 8:45 am] 

BILLING CODE 4910-13-U