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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 99-NM-326-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 747-400 series airplanes. This proposal would require repetitive inspections to detect fatigue cracking of the longeron splice fittings at stringer 11 on the left and right sides at body station 2598, and various follow-on actions. This action is necessary to detect and correct fatigue cracking of the longeron splice fittings and subsequent damage to adjacent structure. Such damage could result in the inability of the structure to carry horizontal stabilizer flight loads, and consequent reduced controllability of the horizontal stabilizer. This action is intended to address the identified unsafe condition. 

# DATES:

Comments must be received by August 14, 2000. 

# ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-326-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9 a.m. and 3 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-326-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, PO 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:

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: 

## 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                           ( print page 39829)                        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 99-NM-326-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-326-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. 

## Discussion 

The FAA has received reports indicating that fatigue cracking was detected on the longeron splice fittings at stringer 11 on certain Boeing Model 747-100, -200, -300, 747SR and 747SP series airplanes. On three airplanes with flight cycles ranging from 16,867 to 27,146, and with flight hours ranging from 30,198 to 62,783, the splice fitting cracks that were detected measured up to 1.5 inches long. The longeron splice fittings on Model 747-400 series airplanes affected by this proposal are identical to those on which the fatigue cracking was detected. Such fatigue cracking, and subsequent damage to adjacent structure, could result in the inability of the structure to carry horizontal stabilizer flight loads, and consequent reduced controllability of the horizontal stabilizer. 

## Related Rulemaking 

This proposed AD is related to AD 2000-10-23, amendment 39-11748 (65 FR 34061, June 30, 2000), which is applicable to certain Boeing Model 747-100, -200, -300,  747SR, and 747SP series airplanes. That AD requires repetitive inspections to detect cracking of the longeron splice fittings at stringer 11, on the left and right sides at body station 2598, and replacement of any cracked fitting with a new fitting. This NPRM proposes similar actions for Boeing Model 747-400 series airplanes. 

## Explanation of Relevant Service Information 

The FAA has reviewed and approved Boeing Alert Service Bulletin 747-53A2419, dated December 17, 1998, which describes procedures for repetitive detailed visual inspections to detect cracking of the longeron splice fittings at stringer 11, on the left and right sides at body station 2598. If no cracking is detected, follow-on actions include rework of the fittings or replacement of the fittings with new fittings, and repetitive inspections to detect cracking. If any cracking is detected, the corrective action is to be accomplished prior to further flight. The corrective action includes replacement of all four longeron splice fittings on the affected side, and repetitive detailed visual inspections to detect cracking. Accomplishment of the actions specified in the alert 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 alert service bulletin described previously, except as discussed below. 

## Differences Between Proposed Rule and Alert Service Bulletin 

Operators should note that, although the alert service bulletin specifies that the manufacturer may be contacted for disposition of certain repair or replacement conditions, this AD requires the repair or replacement 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. 

Operators also should note that the alert service bulletin specifies that the corrective actions required by this proposed AD may be accomplished in accordance with “an operator's equivalent procedure.” However, this proposed AD requires that an “operator's equivalent procedure” may be used only in accordance with the procedures specified in the operator's maintenance manual. 

This proposed AD would mandate rework or replacement of all four longeron splice fittings on the applicable side of the airplane if any of the four fittings on that side are reworked or replaced. The alert service bulletin provides for that action as recommended. 

## Cost Impact 

There are approximately 490 airplanes of the affected design in the worldwide fleet. The FAA estimates that 59 airplanes of U.S. registry would be affected by this proposed AD. 

It would take approximately 2 work hours (1 hour per each side) per airplane to accomplish the proposed 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 $7,080, or $120 per airplane, per inspection cycle. 

It would take approximately 12 work hours (6 hours per each side) per airplane to accomplish the proposed rework or replacement, at an average labor rate of $60 per work hour. Required parts would cost between $731 and $7,906 per airplane. Based on these figures, the cost impact of the proposed rework or replacement on U.S. operators is estimated to be between $1,451 and $8,626 per airplane. 

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                           ( print page 39830)                        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 adding the following new airworthiness directive:

**Boeing:**                                 Docket 99-NM-326-AD.                             

*Applicability:*                                 Model 747-400 series airplanes, as listed in Boeing Alert Service                             

Bulletin 747-53A2419, dated December 17, 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 accordance with paragraph (e) 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 longeron splice fittings and subsequent damage to adjacent structure, which could result in the inability of the structure to carry horizontal stabilizer flight loads, and consequent reduced controllability of the horizontal stabilizer; accomplish the following: 

## Initial Detailed Visual Inspection 

(a) Perform a detailed visual inspection to detect cracking of the longeron fittings at stringer 11, on the left and right sides at body station 2598, at the later of the times specified in paragraphs (a)(1) and (a)(2) of this AD, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2419, dated December 17, 1998. 

(1) Inspect prior to the accumulation of 17,000 total flight cycles or 63,000 total flight hours, whichever occurs first. 

(2) Inspect within 24 months after the effective date of this AD. 

# Note 2:

Where there are differences between the AD and the alert service bulletin, the AD prevails.

# Note 3:

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.”

## Rework/Replacement/Repetitive Inspections 

(b) If no cracking is detected during the inspection required by paragraph (a) of this AD, accomplish the requirements of either paragraph (b)(1), (b)(2), or (b)(3) of this AD. 

(1) Prior to further flight, rework all four longeron splice fittings on the left and right sides at body station 2598, in accordance with Part 3 of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2419, dated December 17, 1998. Repeat the inspection required by paragraph (a) of this AD one time at the later of the times specified in paragraphs (b)(1)(i) and (b)(1)(ii) of this AD, and thereafter at intervals not to exceed 3,000 flight cycles or 18,000 flight hours, whichever occurs first. 

(i) For airplanes on which the rework is accomplished prior to the accumulation of 7,000 total flight cycles and prior to the accumulation of 25,000 total flight hours: Inspect within 20,000 flight cycles or 72,000 flight hours after rework, whichever occurs first. 

(ii) For airplanes on which the rework is accomplished at or after the accumulation of 7,000 total flight cycles, or 25,000 total flight hours: Inspect within 10,000 flight cycles or 36,000 flight hours after rework, whichever occurs first. 

(2) Prior to further flight, replace all four longeron splice fittings on the left and right sides at body station 2598 with new fittings, in accordance with Part 2 of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2419, dated December 17, 1998. Repeat the inspection required by paragraph (a) of this AD one time within 20,000 flight cycles or 72,000 flight hours after the replacement, whichever occurs first; and thereafter at intervals not to exceed 3,000 flight cycles or 18,000 flight hours, whichever occurs first. 

(3) Repeat the inspection required by paragraph (a) of this AD at intervals not to exceed 3,000 flight cycles or 18,000 flight hours, whichever occurs first. 

## Corrective Action/Repetitive Inspections 

(c) If any cracking is detected during any inspection required by paragraph (a) or (b)(3) of this AD, prior to further flight: Replace all four longeron splice fittings on the affected side in accordance with Part 2 of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2419, dated December 17, 1998. Repeat the inspection required by paragraph (a) of this AD one time within 20,000 flight cycles or 72,000 flight hours after the replacement, whichever occurs first; and thereafter at intervals not to exceed 3,000 flight cycles or 18,000 flight hours, whichever occurs first. 

(d) If any cracking is detected during any inspection required by paragraph (b)(1), (b)(2), or (c) of this AD, repair 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. 

# Note 4:

There is no terminating action currently available for the inspections required by this AD.

## Alternative Methods of Compliance 

(e) 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 5:

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 

(f) 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. 

      ( print page 39831)    
Issued in Renton, Washington, on June 22, 2000. 

Donald L. Riggin, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 00-16358 Filed 6-27-00; 8:45 am] 

BILLING CODE 4910-13-U