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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 2000-NM-251-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 all Boeing Model 747 series airplanes. This proposal would require repetitive high frequency eddy current inspections to find cracking of the bulkhead frame support at body station 2598 under the hinge support fittings of the horizontal stabilizer, and repair if cracking is found. This action is necessary to find and fix fatigue cracking in the frame support, which could result in inability of the structure to carry horizontal stabilizer flight loads and reduced controllability of the horizontal stabilizer. This action is intended to address the identified unsafe condition. 

# DATES:

Comments must be received by April 9, 2001. 

# ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-251-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-251-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 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, 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 considered before taking action on the proposed rule. The proposals contained in this action 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                           ( print page 10975)                        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 action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2000-NM-251-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-251-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. 

## Discussion 

The FAA has received a report indicating that a fatigue crack (1.25 inches in length) was found on the bulkhead frame support under the hinge support fittings of the horizontal stabilizer at body station (BS) 2598 on a Model 747-200F series airplane. The airplane had accumulated approximately 13,488 total flight cycles and 58,697 total flight hours at the time the crack was found. Such cracking in the frame support, if not found and fixed, could result in inability of the structure to carry horizontal stabilizer flight loads and reduced controllability of the horizontal stabilizer. 

## Explanation of Relevant Service Information 

The FAA has reviewed and approved Boeing Alert Service Bulletin 747-53A2449, dated June 8, 2000. The service bulletin describes procedures for repetitive open-hole high frequency eddy current inspections to find cracking of the bulkhead frame support located on the left and right sides at BS 2598 under the hinge support fittings of the horizontal stabilizer. If cracking is found, the service bulletin specifies to contact Boeing for repair instructions. 

## 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 bulletin described previously, except as discussed below. 

## Difference Between Service Bulletin and This Proposed AD 

The service bulletin specifies that the manufacturer must be contacted for repair of certain conditions, but this proposal would require the repair of those conditions to be accomplished per a method approved by the FAA, or per 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. For a method to be approved, the approval letter must specifically reference this AD. 

## Cost Impact 

There are approximately 1,314 airplanes of the affected design in the worldwide fleet. The FAA estimates that 258 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 8 work hours (4 work hours per side) per airplane to accomplish the proposed inspections, 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 $123,840, or $480 per airplane, per inspection cycle. 

The cost impact figure discussed above is 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 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 2000-NM-251-AD.                            

*Applicability:*                                 Model 747 series airplanes, as listed in Boeing Alert Service Bulletin 747-53A2449, dated June 8, 2000, 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 (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 find and fix fatigue cracking in the bulkhead frame support at body station (BS) 2598 under the hinge support fittings of the horizontal stabilizer, which could result in inability of the structure to carry horizontal stabilizer flight loads and reduced controllability of the horizontal stabilizer, accomplish the following: 

## Repetitive High Frequency Eddy Current (HFEC) Inspections 

                                (a) Before the accumulation of 10,000 total flight cycles, or within 1,000 flight cycles after the effective date of this AD, whichever occurs later: Do an open-hole HFEC                                       ( print page 10976)                                    inspection to find cracking of the bulkhead frame support under the hinge support fittings of the horizontal stabilizer on the left and right sides at BS 2598, per Figure 2 of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2449, dated June 8, 2000. Repeat the inspection after that at intervals not to exceed 3,000 flight cycles.                             

## Repair 

(b) If any cracking is found during any inspection required by paragraph (a) of this AD, before further flight, repair per a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or per data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative 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. 

## 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 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 2:

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 

(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. 

Issued in Renton, Washington, on February 13, 2001. 

Vi L. Lipski, 

Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 01-4219 Filed 2-20-01; 8:45 am] 

BILLING CODE 4910-13-U