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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 99-NM-330-AD; Amendment 39-11797; AD 2000-12-19] 
          - 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 repetitive inspections of the aft pressure bulkhead to detect cracking, and repair, if necessary. This amendment is prompted by a report of fatigue cracking found in the upper half of the aft pressure bulkhead. The actions specified by this AD are intended to detect and correct cracking in the aft pressure bulkhead, which could result in rapid decompression of the fuselage or overpressurization of the tail section. 

# DATES:

Effective July 28, 2000. 

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of July 28, 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:

Rick Kawaguchi, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-1153; 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 February 2, 2000 (65 FR 4900). That action proposed to require repetitive inspections of the aft pressure bulkhead to detect cracking, and repair, if necessary.                 

## Comments 

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

The commenter supports the proposed rule. 

## Conclusion 

After careful review of the available data, including the comment noted above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed. 

## Cost Impact 

There are approximately 552 airplanes of the affected design in the worldwide fleet. The FAA estimates that 84 airplanes of U.S. registry will be affected by this AD. 

It will take approximately 7 work hours per airplane to accomplish the required detailed visual inspection, at the average labor rate of $60 per work hour. Based on these figures, the cost impact of the required detailed visual inspection on U.S. operators is estimated to be $35,280, or $420 per airplane, per inspection cycle. 

It will take approximately 7 work hours per airplane to accomplish the required HFEC inspections, at the average labor rate of $60 per work hour. Based on these figures, the cost impact of the required HFEC inspections on U.S. operators is estimated to be $35,280, or $420 per airplane, per inspection cycle. 

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. 

## Regulatory Impact 

The regulations adopted herein will 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 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: 

**2000-12-19 Boeing:**                             Amendment 39-11797. Docket 99-NM-330-AD.                        

*Applicability:*                             Model 747 series airplanes, as listed in Boeing Alert Service Bulletin 747-53A2425, dated October 29, 1998; 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                                       ( print page 39077)                                    accordance with paragraph (g) 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 cracking in the aft pressure bulkhead, which could result in rapid decompression of the fuselage or overpressurization of the tail section, accomplish the following: 

## Initial and Repetitive Inspections 

(a) Except as provided by paragraph (f) of this AD, prior to the accumulation of 20,000 total flight cycles, or within 12 months after the effective date of this AD, whichever occurs later, perform a detailed visual inspection of the upper half of the aft pressure bulkhead to detect cracking, in accordance with Figure 6 or 7, as applicable, of Boeing Alert Service Bulletin 747-53A2425, dated October 29, 1998. Repeat the detailed visual inspection thereafter at intervals not to exceed 1,500 flight cycles. For areas of the upper half of the aft pressure bulkhead that have been repaired previously, this detailed visual inspection may be deferred for up to 15,000 flight cycles after accomplishment of the repair, as described in the NOTE in paragraph 3.D. of the Accomplishment Instructions of the alert 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.” 

(b) Except as provided by paragraph (f) of this AD, if no cracking is detected during the initial detailed visual inspection required by paragraph (a) of this AD: Within 1,500 flight cycles after accomplishment of that inspection, perform a high frequency eddy current (HFEC) inspection of the upper and lower halves of the aft pressure bulkhead to detect cracking, in accordance with Figure 8 of Boeing Alert Service Bulletin 747-53A2425, dated October 29, 1998. Repeat the HFEC inspection thereafter at intervals not to exceed 3,000 flight cycles. 

(c) Except as provided by paragraph (f) of this AD, if any cracking is detected during any inspection required by paragraph (a) of this AD: Prior to further flight, perform an HFEC inspection of the upper and lower halves of the aft pressure bulkhead to detect cracking, in accordance with Figure 8 or 9, as applicable, of Boeing Alert Service Bulletin 747-53A2425, dated October 29, 1998. Repeat the HFEC inspection thereafter at intervals not to exceed 3,000 flight cycles. 

## Repair 

(d) Except as provided by paragraphs (e) and (f) of this AD, if any cracking is detected during any inspection required by paragraph (a), (b), or (c) of this AD: Prior to further flight, repair in accordance with Boeing Alert Service Bulletin 747-53A2425, dated October 29, 1998. 

(e) If any cracking is detected during any inspection required by paragraph (a), (b), or (c) of this AD, and Boeing Alert Service Bulletin 747-53A2425, dated October 29, 1998, specifies to contact Boeing for repair instructions: Repair any cracking, prior to further flight, in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate; or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative (DER) who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the approval letter must specifically reference this AD. 

## Operator's “Equivalent Procedure” 

(f) Where Boeing Alert Service Bulletin 747-53A2425, dated October 29, 1998, specifies that an inspection or a repair, as applicable, may be accomplished in accordance with an operator's “equivalent procedure”: The inspection or repair, as applicable, must be accomplished in accordance with the applicable chapter of the Boeing 747 Maintenance Manual or the Boeing 747 Structural Repair Manual specified in the alert service bulletin. 

## Alternative Methods of Compliance 

(g) 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 

(h) 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. 

## Incorporation by Reference 

(i) Except as provided by paragraphs (e) and (f) of this AD, the actions shall be done in accordance with Boeing Alert Service Bulletin 747-53A2425, dated October 29, 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.

(j) This amendment becomes effective on July 28, 2000.

Issued in Renton, Washington, on June 12, 2000. 

Donald L. Riggin, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 00-15308 Filed 6-22-00; 8:45 am] 

BILLING CODE 4910-13-P