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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 2000-NM-184-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 Boeing Model 757-200 series airplanes, that currently requires inspections to detect cracking on the free edge of the tang, if necessary, and of the fastener holes in the lower spar chord; and various follow-on actions. That AD also provides for an optional terminating action for the repetitive inspections. This action would add inspections to detect additional cracking of the fastener holes in the lower spar chord. This action also adds an optional terminating modification. This proposal is prompted by the issuance of new service information. The actions specified by the proposed AD are intended to detect and correct fatigue cracking in the lower spar chord, which could result in reduced structural integrity of the engine 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. 2000-NM-184-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-184-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                               ( print page 60130)                            98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.                     

# FOR FURTHER INFORMATION CONTACT:

Dennis Stremick, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2776; 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-184-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-184-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. 

## Discussion 

On March 5, 1997, the FAA issued AD 97-06-04, amendment 39-9961 (62 FR 11760, March 13, 1997), applicable to certain Boeing Model 757-200 series airplanes, to require inspections to detect cracking on the free edge of the tang, if necessary, and of the fastener holes in the lower spar chord; and various follow-on actions. That AD also provides for optional terminating action for the repetitive inspections. That action was prompted by a report of fatigue cracking in the lower spar chord of two Model 757 series airplanes. The requirements of that AD are intended to detect and correct such fatigue cracking, which could result in reduced structural integrity of the engine strut. 

## Related Rulemaking 

This proposed AD is related to AD 99-24-07, amendment 39-11431 (64 FR 66370, November 26, 1999), applicable to certain Boeing Model 757 series airplanes equipped with Rolls Royce RB211 engines, that requires modification of the nacelle strut and wing structure. In the preamble to AD 97-06-04, the FAA specified that the actions required by that AD were considered “interim action” and that the manufacturer was developing a modification to positively address the unsafe condition. The FAA indicated that it may consider further rulemaking action once the modification was developed, approved, and available. The manufacturer now has developed such a modification, and the FAA issued AD 99-24-07 to require accomplishment of that modification. 

## Actions Since Issuance of Previous Rule 

Since the issuance of AD 97-06-04, the FAA has reviewed and approved Boeing Service Bulletin 757-54-0031, Revision 4, dated November 11, 1999, which describes procedures for additional bolt hole inspections to detect further cracking of the fastener holes that promulgated in a different direction in the lower spar chord than the area described in that AD. This inspection was added due to a report of a crack in the lower spar chord on a Model 757 series airplane with fewer flight cycles than the number of flight cycles stated in the threshold table of Boeing Service Bulletin 757-54-0031, Revision 2, dated December 19, 1996. Revision 2 was referenced as the appropriate source of service information for accomplishment of the actions required by AD 97-06-04, but did not include the lower spar chord area specified in Revision 4. 

## 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 supersede AD 97-06-04 to continue to require inspections to detect cracking on the free edge of the tang, if necessary, and of the fastener holes in the lower spar chord; and various follow-on actions. This proposed AD also would continue to provide an optional terminating action for the repetitive inspections. This new action would add inspections to detect additional cracking of the fastener holes in the lower spar chord. This action also adds an optional terminating modification. The actions would be required to be accomplished in accordance with the service bulletin described previously, except as discussed below. 

## Difference Between Service Bulletin and This AD 

Operators should note that, although the service bulletin referenced in this AD recommends accomplishment of the second eddy current inspection within 6,000 flight cycles after accomplishment of the first inspection, this AD adds a “grace period” of 60 days due to the length of time that has passed since the issuance of that AD. The FAA has been advised that a significant number of the affected Model 757 series airplanes have already accomplished the first inspection. In developing an appropriate compliance time for this action, the FAA considered not only the degree of urgency associated with addressing the subject unsafe condition, but the manufacturer's recommendation as to an appropriate compliance time, parts availability, and the practical aspect of accomplishing the required inspection within an interval of time that parallels the normal scheduled maintenance for the majority of affected operators. 

In light of this, the FAA has determined that, for operators that have already accomplished the first inspection, a “grace period” of 60 days is necessary to ensure that the affected airplanes are inspected in a timely manner and that an acceptable level of safety is maintained. 

## Cost Impact 

There are approximately 418 Model 757-200 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 151 airplanes of U.S. registry would be affected by this proposed AD. 

                    The inspections that are currently required by AD 97-06-04 take                           ( print page 60131)                        approximately 52 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the currently required actions on U.S. operators is estimated to be $471,120, or $3,120 per airplane.                 

The new inspections that are proposed in this AD action would take approximately 4 work hours per inspection, per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed requirements of this AD on U.S. operators is estimated to be $36,240, or $240 per airplane. 

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 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 39-9961 (62 FR 11760, March 13, 1997), and by adding a new airworthiness directive (AD), to read as follows: 

**Boeing:**                                 Docket 2000-NM-184-AD. Supersedes AD 97-06-04, Amendment 39-9961.                             

*Applicability:*                                 Model 757-200 series airplanes having line numbers 1 through 736 inclusive, powered by Rolls Royce engines, 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 (n) 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 detect and correct fatigue cracking of the lower spar chord, which could result in reduced structural integrity of the engine strut, accomplish the following: 

## Restatement of Requirements of AD 97-06-04

### Repetitive Inspections 

(a) Prior to the accumulation of 15,000 total flight cycles, or within 60 days after March 28, 1997 (the effective date of AD 97-06-04, amendment 39-9961), whichever occurs later: Perform an eddy current inspection to detect cracking on the free edge of the tang, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 757-54-0031, Revision 2, dated December 19, 1996, or Revision 4, dated November 11, 1999. Repeat this inspection thereafter at intervals not to exceed 3,000 flight cycles until the inspection required by paragraph (d) of this AD is accomplished. 

# Note 2:

The inspection required by paragraph (a) of this AD need not be performed on airplanes on which the inspection required by paragraph (d) of this AD is performed prior to the compliance time specified in paragraph (a) of this AD.

### Follow-On Actions 

(b) If any cracking is found during the inspection required by paragraph (a) of this AD, and the cracking is within the limits specified in Boeing Service Bulletin 757-54-0031, Revision 2, dated December 19, 1996, or Revision 4, dated November 11, 1999: Prior to further flight, remove the midchord channels, stop-drill the cracking, and install a repair in accordance with the service bulletin. No further action is required by paragraph (a) of this AD. 

(c) If any cracking is found, and the cracking is outside the limits specified in Boeing Service Bulletin 757-54-0031, Revision 2, dated December 19, 1996, or Revision 4, dated November 11, 1999: Prior to further flight, replace the lower spar chord with a new or serviceable chord in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA. 

### Bolt Hole Inspection 

(d) Perform an eddy current inspection (bolt hole inspection) to detect cracking of the two fastener holes in the lower spar chord, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 757-54-0031, Revision 2, dated December 19, 1996, or Revision 4, dated November 11, 1999, at the time specified in paragraph (d)(1) and (d)(2) of this AD, as applicable. Accomplishment of this inspection terminates the inspections required by paragraph (a) of this AD. 

(1) For airplanes on which the stiffening straps have been removed from the midchord in accordance with Boeing Service Bulletin 757-54-0028 prior to the effective date of this AD: Accomplish the inspection at the time specified in Paragraph 1.D. (“Description”) of Boeing Service Bulletin 757-54-0031, Revision 2, dated December 19, 1996, or Revision 4, dated November 11, 1999. 

(2) For airplanes other than those identified in paragraph (d)(1) of this AD: Accomplish the inspection prior to the accumulation of 18,000 total flight cycles, or within 60 days after March 28, 1997, whichever occurs later. 

(e) Accomplish either paragraph (e)(1) or (e)(2) of this AD, as applicable, in accordance with Boeing Service Bulletin 757-54-0031, Revision 2, dated December 19, 1996, or Revision 4, dated November 11, 1999. 

                                (1) If any fastener installed as a result of an inspection required by paragraph (d) of this AD has a diameter of                                 5/8                                -inch or greater: Install the repair prior to the accumulation of the number of flight cycles specified in the “Subsequent Inspection Interval” column of the Threshold Table included in Paragraph 1.E. (“Compliance”) of Boeing Service Bulletin 757-54-0031, Revision 2, dated December 19, 1996, or Revision 4, dated November 11, 1999.                             

                                (2) If any fastener installed as a result of an inspection required by paragraph (d) of this AD has a diameter of less than                                 5/8                                -inch: Repeat the bolt hole inspection required by                                       ( print page 60132)                                    paragraph (d) of this AD prior to the accumulation of the number of flight cycles specified in the “Subsequent Inspection Interval” column of the Threshold Table included in Paragraph 1.E. (“Compliance”) of the service bulletin until the repair specified in paragraph (h) of this AD is installed.                             

### Optional Terminating Action 

(f) Installation of the repair in accordance with the Accomplishment Instructions of Boeing Service Bulletin 757-54-0031, Revision 2, dated December 19, 1996, or Revision 4, dated November 11, 1999, constitutes terminating action for the requirements in paragraphs (a) and (d) of this AD. 

## New Requirements of This AD

### Revised Service Information 

(g) Except as provided by paragraphs (c) and (l)(3) of this AD: As of the effective date of this new AD, Boeing Service Bulletin 757-54-0031, Revision 4, dated November 11, 1999, must be used for accomplishment of the actions required by this AD. 

### Second Bolt Hole Inspection 

(h) Within 6,000 flight cycles after accomplishment of paragraph (d) of this AD, or within 60 days after the effective date of this AD, whichever occurs later: Perform a second eddy current inspection (bolt hole inspection) to detect cracking of the two fastener holes in the lower spar chord, in accordance with Part IV of the Accomplishment Instructions of Boeing Service Bulletin 757-54-0031, Revision 4, dated November 11, 1999. If no cracking is found during the inspection required by this paragraph, no further action is required by this paragraph. 

### Third Bolt Hole Inspection 

(i) After accomplishment of the inspection required by paragraph (h) of this AD, when the airplane has reached the flight cycle threshold as defined by the flight cycle threshold formula on page 9, Paragraph 1.E. (“Compliance”) of Boeing Service Bulletin 757-54-0031, Revision 4, dated November 11, 1999: Perform a third eddy current inspection (bolt hole inspection) to detect cracking of the two fastener holes in the lower spar chord, in accordance with Part II of the Accomplishment Instructions of the service bulletin. 

### Fourth Bolt Hole Inspection 

(j) If, after accomplishment of the inspection required by paragraph (i) of this AD, paragraph (m) of this AD has not yet been accomplished: When the airplane has reached the flight cycle threshold as defined by the flight cycle threshold formula on page 9, Paragraph 1.E. (“Compliance”) of Boeing Service Bulletin 757-54-0031, Revision 4, dated November 11, 1999; perform a fourth eddy current inspection (bolt hole inspection) to detect cracking of the two fastener holes in the lower spar chord, in accordance with Part II of the Accomplishment Instructions of the service bulletin. 

### Follow-On Actions 

(k) If no cracking is found during any inspection required by paragraph (d), (i), or (j) of this AD, prior to further flight, increase the diameter of the holes by the dimensions specified in the Accomplishment Instructions of Boeing Service Bulletin 757-54-0031, Revision 2, dated December 19, 1996, or Revision 4, dated November 11, 1999, and install new fasteners in accordance with the service bulletin. 

(l) If any cracking is found during any inspection required by paragraph (d), (h), (i), or (j) of this AD, prior to further flight, accomplish paragraph (l)(1), (l)(2), or (l)(3) of this AD, as applicable, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 757-54-0031, Revision 2, dated December 19, 1996, or Revision 4, dated November 11, 1999. 

(1) If the cracking can be removed by increasing the diameter of the hole in accordance with the service bulletin: Increase the diameter of the hole by the dimensions specified in the Accomplishment Instructions of the service bulletin, and install new fasteners in accordance with the service bulletin. 

(2) If the cracking cannot be removed by increasing the diameter of the hole in accordance with the Accomplishment Instructions of the service bulletin, but the cracking is within the limits specified in the service bulletin: Install the repair in accordance with the service bulletin. No further action is required by paragraph (d) of this AD. 

(3) If the cracking is outside the limits specified in the service bulletin: Replace the lower spar chord with a new or serviceable chord in accordance with a method approved by the Manager, Seattle ACO. 

### Optional Terminating Modification 

(m) Accomplishment of the modification of the nacelle strut and wing structure as required by AD 99-24-07, amendment 39-11431, constitutes terminating action for the requirements of this AD. 

### Alternative Methods of Compliance 

(n) 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 Permits 

(o) 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. 00-25969 Filed 10-6-00; 8:45 am] 

BILLING CODE 4910-13-U