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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39
          - [Docket No. 99-NM-127-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 engines. This proposal would require modification of the nacelle strut and wing structure. This proposal is prompted by reports indicating that the actual operational loads applied to the nacelle are higher than the analytical loads that were used during the initial design. Such an increase in loading can lead to fatigue cracking in the primary strut structure prior to an airplane reaching its design service objective. The actions specified by the proposed AD are intended to prevent fatigue cracking in the primary strut structure and consequent reduced structural integrity of the strut.

# 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. 99-NM-127-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. 99-NM-127-AD” in the subject line and need not be submitted in triplicate. Comments sent                               ( print page 60127)                            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 G. 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.

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-127-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-127-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

## Discussion

The FAA has received reports indicating that the airplane manufacturer has accomplished a structural reassessment of the damage tolerance capabilities of the Boeing Model 767 series airplane powered by General Electric engines. This reassessment 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 flight cycles. Analysis also indicates that such cracking, if it were to occur, would grow at a much greater rate than originally expected. Fatigue cracking in the primary strut structure would result in reduced structural integrity of the strut.

## Explanation of Relevant Service Information

Boeing recently has developed a modification of the strut-to-wing attachment structure installed on Model 767 series airplanes powered by General Electric engines. This modification significantly improves the load-carrying capability and durability of the strut-to-wing attachments. Such improvements also will substantially reduce the possibility of fatigue cracking and corrosion developing in the attachment assembly.

The FAA has reviewed and approved Boeing Service Bulletin 767-54-0081, dated July 29, 1999, which describes procedures for modification of the nacelle strut and wing structure. The modification consists of replacing many of the significant load-bearing components of the strut and wing (e.g., the side link fittings, the midspar fittings, the side load fittings, certain fuse pins assemblies, etc.) with improved components.

The service bulletin contains a formula for calculating an optional compliance threshold for the specified modification. This formula is intended to be used as an alternative to the 20-year calendar threshold specified in the service bulletin.

In addition, Table 2 of the service bulletin also identifies six related service bulletin modifications that must be accomplished before or at the same time as the modification in Boeing Service Bulletin 767-54-0081:
    -  Boeing Service Bulletin 767-29-0057:                      The FAA has reviewed and approved Boeing Service Bulletin 767-29-0057, dated December 16, 1993, which describes procedures for modification of the electrical wiring support of the alternating current motor pump of the main hydraulic power system. The modification involves installing new band clamps and index-straps, and on certain airplanes, installing new wire support brackets on the strut bulkhead.                
    -  Boeing Service Bulletin 767-54-0069:                      The FAA has reviewed and approved Boeing Service Bulletin 767-54-0069, Revision 1, dated January 29, 1998, which describes procedures for rework of the side load fitting and tension fasteners, as applicable, and replacement of midspar fuse pins with new, higher-strength midspar fuse pins. The rework involves increasing the size of the tension bolts of the inboard and outboard side load fittings. The replacement also involves installing new, higher-strength bolts and radius fillers in the side load fittings and backup support structure, and installing higher-strength fasteners common to the front spar and rib number 8 rib post.                
    -  Boeing Service Bulletin 767-54-0083:                      The FAA has reviewed and approved Boeing Service Bulletin 767-54-0083, dated September 17, 1998, which describes procedures for replacement of the upper link with a new, improved part that will increase the strength and durability of the upper link installation. That service bulletin also describes procedures for modification of the wire support bracket attached to the upper link.                
    -  Boeing Service Bulletin 767-54-0088:                      The FAA has reviewed and approved Boeing Service Bulletin 767-54-0088, Revision 1, dated July 29, 1999, which describes procedures for replacement of the upper link fuse pin and aft pin with new, improved pins that will increase the strength and durability of the upper link installation.                
    -  Boeing Service Bulletin 767-54A0094:                      The FAA has previously reviewed and approved Boeing Service Bulletin 767-54A0094, Revision 1, dated September 16, 1999. This service bulletin is referenced as the appropriate service information for accomplishing the actions required in AD 2000-07-05, amendment 39-11659, which was issued March 31, 2000 ( 65 FR 18883 , April 10, 2000). This service bulletin describes procedures for repetitive detailed visual inspections to detect cracking of the one-piece diagonal brace of the forward and aft lugs, and corrective actions, if necessary. The corrective actions involve installing a new, three-piece diagonal brace, which eliminates the need for the repetitive inspections. The service bulletin also describes procedures for rework of the three-piece diagonal brace, which                            ( print page 60128)                          increases the inspection intervals of the three-piece diagonal brace.                
    -  Boeing Service Bulletin 767-57-0053:                      Boeing Service Bulletin 767-54-0081 lists Boeing Service Bulletin 767-57-0053, Revision 1, however, the FAA has previously reviewed and approved Boeing Service Bulletin 767-57-0053, Revision 2, dated September 23, 1999. This service bulletin is referenced as the appropriate source of service information for accomplishing the actions required in AD 2000-12-17, amendment 39-11795, which was issued June 9, 2000 ( 65 FR 37843 , June 19, 2000). Revision 1 also is acceptable for compliance with the requirements in that AD. Revision 2 of the service bulletin describes procedures for repetitive ultrasonic and eddy current inspections of the pitch load fitting lugs of the wing front spar for cracking, and rework of the fitting, if necessary.                

Accomplishment of the actions specified in the service bulletins 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 bulletins described previously, except as discussed below.

## Differences Between Proposed Rule and Service Bulletin

Operators should note that, although Boeing Service Bulletin 767-54-0081 specifies that the manufacturer may be contacted for disposition of certain damage conditions that may be detected during accomplishment of the modification, this proposal would require the repair of those conditions to be accomplished in accordance with a method approved by the FAA.

## Cost Impact

There are approximately 381 airplanes of the affected design in the worldwide fleet. The FAA estimates that 159 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 1,006 work hours, including time for gaining access and closing up, per airplane to accomplish the proposed modification in Boeing Service Bulletin 767-54-0081, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $9,597,240, or $60,360 per airplane.

It would take approximately 16 work hours per airplane to accomplish the proposed actions described in Boeing Service Bulletin 767-29-0057, at an average labor rate of $60 per work hour. Required parts would be provided at no cost by the airplane manufacturer. Based on these figures, the cost impact of these proposed actions on U.S. operators is estimated to be $152,640, or $960 per airplane. 

It would take approximately 106 work hours per airplane to accomplish the actions described in Boeing Service Bulletin 767-53-0069, Revision 1, at an average labor rate of $60 per work hour. Required parts would be provided at no cost by the airplane manufacturer. Based on these figures, the cost impact of these proposed actions on U.S. operators is estimated to be $1,011,240, or $6,360 per airplane.

It would take approximately 1 work hour per airplane to accomplish the actions described in Boeing Service Bulletin 767-54-0083, at an average labor rate of $60 per work hour. Required parts would be provided at no cost by the airplane manufacturer. Based on these figures, the cost impact of these proposed actions on U.S. operators is estimated to be $9,540, or $60 per airplane. 

It would take approximately 4 work hours per airplane to accomplish the actions described in Boeing Service Bulletin 767-54-0088, Revision 1, at an average labor rate of $60 per work hour. Required parts would be provided at no cost by the airplane manufacturer. Based on these figures, the cost impact of these proposed actions on U.S. operators is estimated to be $38,160, or $240 per airplane. 

It would take approximately 20 work hours per airplane to accomplish the proposed actions described in Boeing Service Bulletin 767-54A0094, Revision 1, at an average labor rate of $60 per work hour. Required parts would be provided at no cost by the airplane manufacturer. Based on these figures, the cost impact of these proposed actions on U.S. operators is estimated to be $190,800, or $1,200 per airplane. Because the actions described in this service bulletin are already required by another AD action, this proposed requirement would add no new costs for affected operators. 

It would take approximately 5 work hours per airplane to accomplish the proposed actions described in Boeing Service Bulletin 767-57-0053, Revision 2, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of these proposed actions on U.S. operators is estimated to be $47,700, or $300 per airplane. Because the actions described in this service bulletin are already required by another AD action, this proposed requirement would add no new costs for affected operators. 

Some operators may have accomplished certain modifications on some or all of the airplanes in their fleets, while other operators may not have accomplished any of the modifications on any of the airplanes in their fleets. As indicated earlier in this preamble, the FAA invites comments specifically on the overall economic aspects of this proposed rule. 

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. 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                           ( print page 60129)                        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:

**Boeing:**                                 Docket 99-NM-127-AD.                            

*Applicability:*                                 Model 767 series airplanes powered by General Electric engines, line numbers 1 through 663 inclusive, 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 (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 the primary strut structure and consequent reduced structural integrity of the strut, accomplish the following: 

## Modification 

(a) Modify the nacelle strut and wing structure on both the left and right sides of the airplane, in accordance with Boeing Service Bulletin 767-54-0081, dated July 29, 1999, at the later of the times specified in paragraphs (a)(1) and (a)(2) of this AD. 

(1) Prior to the accumulation of 37,500 total flight cycles, or within 20 years since date of manufacture, whichever occurs first. Use of the optional threshold formula described in Figure 1 on page 54 of the service bulletin is an acceptable alternative to the 20-year threshold provided that the conditions specified in Figure 1 of the service bulletin are met. 

(2) Within 3,000 flight cycles after the effective date of this AD. 

(b) Prior to or concurrently with the accomplishment of the modification of the nacelle strut and wing structure required by paragraph (a) of this AD; as specified in paragraph 1.D., Table 2, “Prior or Concurrent Service Bulletins,” on page 8 of Boeing Service Bulletin 767-54-0081, dated July 29, 1999; accomplish the actions specified in Boeing Service Bulletin 767-29-0057, dated December 16, 1993; Boeing Service Bulletin 767-54-0069, Revision 1, dated January 29, 1998; Boeing Service Bulletin 767-54-0083, dated September 17, 1998; Boeing Service Bulletin 767-54-0088, Revision 1, dated July 29, 1999; Boeing Service Bulletin 767-54A0094, Revision 1, dated September 16, 1999; and Boeing Service Bulletin 767-57-0053, Revision 2, dated September 23, 1999; as applicable, in accordance with those service bulletins. 

# Note 2:

AD 2000-12-17, amendment 39-11795, requires accomplishment of Boeing Service Bulletin 767-57-0053, Revision 2, dated September 23, 1999. However, inspections and rework accomplished in accordance with Boeing Service Bulletin 767-57-0053, Revision 1, dated October 31, 1996, are acceptable for compliance with the applicable actions required by paragraph (b) of this AD.

# Note 3:

AD 2000-07-05, amendment 39-11659, requires accomplishment of Boeing Service Bulletin 767-54A0094, dated May 22, 1998. However, inspections and rework accomplished in accordance with Boeing Service Bulletin 767-54A0094, dated May 22, 1998, are acceptable for compliance with the applicable actions required by paragraph (b) of this AD. 

(c) If any damage to the airplane structure is found during the accomplishment of the modification required by paragraph (a) of this AD, and the service bulletin specifies to contact Boeing for appropriate action: Prior to further flight, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, or a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make such findings. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the Manager's approval letter must specifically reference this AD. 

## 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 4:

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

## Special Flight Permits 

(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. 00-25967 Filed 10-6-00; 8:45 am] 

BILLING CODE 4910-13-U