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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 2000-NM-98-AD; Amendment 39-11938; AD 2000-21-06] 
          - RIN 2120-AA64 

# AGENCY:

Federal Aviation Administration, DOT. 

# ACTION:

Final rule. 

# SUMMARY:

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that requires a detailed visual inspection to detect evidence of wear or contact between the precooler support fitting and link assembly; and rework and reidentification of the fitting. This amendment is prompted by a report of rupturing of a diffuser case on a PW JT9D-7Q engine due to cracking in the outer pressure wall in the rear skirt area. The actions specified by this AD are intended to prevent contact between the precooler support link and the precooler support fitting, which could contribute to an uncontained failure of the diffuser case and damage to the airplane. 

# DATES:

Effective November 24, 2000. 

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of November 24, 2000. 

# ADDRESSES:

The service information referenced in this AD may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the Federal Aviation Administration (FAA), Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. 

# FOR FURTHER INFORMATION CONTACT:

Dionne Krebs, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2250; fax (425) 227-1181. 

# SUPPLEMENTARY INFORMATION:

                    A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Boeing Model 747 series airplanes was published in the                     **Federal Register**                     on                           ( print page 63007)                        May 3, 2000 (65 FR 25696). That action proposed to require a detailed visual inspection to detect evidence of wear or contact between the precooler support fitting and link assembly; and rework and reidentification of the fitting.                 

## Comments 

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. 

## Request for Correction of Part Number 

One commenter states that the reidentification part number (P/N) 65B09024-601, as specified in paragraphs (a)(1), (a)(2), and (b) of the proposal, is incorrect, and should be revised to P/N 65B90924-601. The FAA concurs with the commenter's statement; there was an error in the part number specified in the proposed rule and it has been corrected in the applicable paragraphs of the final rule. 

## Action Taken to Address Root Cause 

One commenter repeats a sentence in the Discussion section of the proposal which states, “The diffuser case fracture was due to a crack that most likely developed in a toolmark that was left by a blending operation adjacent to the dog-bone-shaped embossment at the 11 o'clock circumferential location of the outer pressure wall of the case in the area of the rear skirt.” The commenter requests information on the action that has been taken to address the toolmark and blending issue that is the apparent root cause of the unsafe condition. 

The FAA previously issued AD 99-04-05, amendment 39-11029 (64 FR 6784, February 11, 1999), which addresses the toolmark and blending issue. That AD requires a fluorescent penetrant inspection (FPI) of the rear skirt of the diffuser case for cracks, and, if necessary, blending down to a minimum wall thickness to remove cracks and subsequent FPI to determine if cracks have been removed, polishing, and shotpeening. If the cracks are shown by subsequent FPI not to have been removed, that AD requires removing the diffuser case from service and replacing it with a serviceable part. No change to this final rule is necessary in this regard. 

## Request to Reference New Service Information 

One commenter requests the proposal be revised to reference Boeing Service Bulletin 747-36-2135 for accomplishment of the bracket modification. The commenter states that Boeing Service Letter 747-SL-36-089, dated August 10, 1998 (the service information referenced in the proposal for accomplishment of the bracket modification), will be revised to refer to the new service bulletin for the modification instructions. The commenter disagrees with the wording in the proposal stating that the service letter will be revised to reidentify the P/N on the bracket, and plans to revise the service letter to reference the new service bulletin, which will contain modification instructions for the bracket. 

The FAA does not concur with the commenter's request. The referenced service bulletin has not been submitted for review and approval by the FAA; therefore, the final rule cannot be revised to cite as-yet unapproved service information. However, under the provisions of paragraph (c) of the final rule, the FAA may approve requests for an alternative method of compliance in accordance with Boeing Service Bulletin 747-36-2135 after it has been approved by the FAA and submitted to substantiate that such an adjustment would provide an acceptable level of safety that addresses the identified unsafe condition. Additionally, the proposal does not state that the service letter will be revised to reidentify the P/N on the bracket. No change to the final rule is necessary in this regard. 

## Request to Extend Compliance Time 

One commenter requests the proposed compliance time for accomplishment of the detailed visual inspection be extended to “Within 8,000 flight hours after the effective date of this AD,” with no calendar grace period. The commenter states that, since removal of the precooler is necessary to accomplish the rework, the task is best accomplished during a scheduled ‘L,’ ‘H,’ or ‘M’ maintenance check of the airplane. The commenter also states that an extension of the compliance time will ensure that it can accomplish the inspection on all of its affected airplanes during one of the scheduled checks described above. 

The FAA does not concur with the commenter's request. 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, and the practical aspect of accomplishing the required inspection and rework within an interval of time that parallels the normal scheduled maintenance for the majority of affected operators. The FAA has determined that 6,000 hours, time-in-service or 18 months represents an appropriate compliance time allowable for the inspection and rework to be accomplished during scheduled maintenance intervals. However, under the provisions of paragraph (c) of the final rule, the FAA may approve requests for adjustments to the compliance time if data are submitted to substantiate that such an adjustment would provide an acceptable level of safety.

## Conclusion 

After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD. 

## Cost Impact 

There are approximately 79 airplanes of the affected design in the worldwide fleet. The FAA estimates that 27 airplanes of U.S. registry will be affected by this AD. 

It will take approximately 2 work hours per airplane to accomplish the required inspection, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the required inspection on U.S. operators is estimated to be $3,240, or $120 per airplane. 

It will take approximately 16 work hours per airplane to accomplish the required rework, at an average labor rate of $60 per work hour. No parts are required to accomplish the rework. Based on these figures, the cost impact of the required rework on U.S. operators is estimated to be $25,920, or $960 per airplane. 

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the 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 adopted herein will not have a substantial direct effect on the States, on the relationship between                           ( print page 63008)                        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 final rule does not have federalism implications under Executive Order 13132.                 

                    For the reasons discussed above, I certify that this action (1) is not a “significant regulatory action” under Executive Order 12866; (2) is not a “significant rule” under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption                     **ADDRESSES.**

# List of Subjects in 14 CFR Part 39

      - Air transportation
      - Aircraft
      - Aviation safety
      - Incorporation by reference
      - Safety

## Adoption of the Amendment 

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 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: 

**2000-21-06 Boeing:**                             Amendment 39-11938. Docket 2000-NM-98-AD.                         

*Applicability:*                             Model 747 series airplanes, certificated in any category; equipped with Pratt & Whitney JT9D-7Q and JT9D-7Q3 turbofan engines.                         

# 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 contact between the precooler support link and the precooler support fitting, which could contribute to an uncontained failure of the diffuser case and damage to the airplane, accomplish the following: 

## Detailed Visual Inspection 

(a) For any precooler support fitting having P/N 65B90924-1 or P/N 65B90924-600 that has not been reworked to the dimensions specified in Boeing Service Letter 747-SL-36-089, dated August 10, 1998: Within 6,000 hours time-in-service after the effective date of this AD, or within 18 months after the effective date of this AD, whichever occurs first, perform a detailed visual inspection to detect evidence of contact wear or contact between the precooler support fitting and link assembly, P/N 69B93162-1 or 69B93162-3, in accordance with the service letter. 

## Rework and Reidentification 

(1) If no evidence of contact wear or contact between the precooler support fitting and link assembly is found: At the next engine removal, rework the precooler support fitting to the dimensions specified in the service letter, in accordance with the service letter; and permanently and legibly reidentify the support fitting as P/N 65B90924-601. 

(2) If any evidence of contact wear or contact between the precooler support fitting and link assembly is found: Prior to further flight, rework the precooler support fitting to the dimensions specified in the service letter, in accordance with the service letter; and permanently and legibly reidentify the support fitting as P/N 65B90924-601. 

# 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.” 

## Reidentification 

(b) For any precooler support fitting having P/N 65B90924-1 or P/N 65B90924-600 that has been reworked to the dimensions specified in Boeing Service Letter 747-SL-36-089, dated August 10, 1998, but has not been permanently and legibly reidentified: Within 6,000 hours time-in-service or 18 months after the effective date of this AD, whichever occurs first, permanently and legibly reidentify the reworked fitting as P/N 65B90924-601. 

## 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, Seattle Aircraft Certification Office (ACO), FAA. 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 

(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. 

## Incorporation by Reference 

(e) Except as provided by paragraphs (a)(1), (a)(2), and (b) of this AD, the actions shall be done in accordance with Boeing Service Letter 747-SL-36-089, including attachment, dated August 10, 1998. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. 

## Effective Date 

(f) This amendment becomes effective on November 24, 2000.

Issued in Renton, Washington, on October 13, 2000. 

Donald L. Riggin, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

[FR Doc. 00-26878 Filed 10-19-00; 8:45 am] 

BILLING CODE 4910-13-P