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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. FAA-2004-19203; Directorate Identifier 2004-NM-109-AD] 
          - RIN 2120-AA64 

# AGENCY:

Federal Aviation Administration (FAA), DOT. 

# ACTION:

Notice of proposed rulemaking (NPRM). 

# SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 757-200 series airplanes. This proposed AD would require modifying the frequency converters located in the closet assembly in the passenger compartment, and making various wiring changes in and between the closet assembly and forward purser work station. This proposed AD also would require modifying the in-flight entertainment system prior to or concurrently with the modification of the frequency converters. This proposed AD is prompted by a certification review that revealed a frequency converter failure mode not identified in the original system design. We are proposing this AD to prevent a short circuit between the frequency converter output and the distribution circuit breakers, which could result in overheating and failure of adjacent wiring and consequent degraded operation of airplane systems. 

# DATES:

We must receive comments on this proposed AD by November 15, 2004. 

# ADDRESSES:

Use one of the following addresses to submit comments on this proposed AD. 
      - DOT Docket web site: Go to http://dms.dot.gov                          and follow the instructions for sending your comments electronically.                     
      - Government-wide rulemaking web site: Go to http://www.regulations.gov                          and follow the instructions for sending your comments electronically.                     
      - Mail: Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street SW., Nassif Building, room PL-401, Washington, DC 20590.
      - By fax: (202) 493-2251.
      - Hand Delivery: Room PL-401 on the plaza level of the Nassif Building, 400 Seventh Street SW., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

For service information identified in this proposed AD, contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207. 

                        You can examine the contents of this AD docket on the Internet at                         *http://dms.dot.gov,*                         or at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street SW., room PL-401, on the plaza level of the Nassif Building, Washington, DC. This docket number is FAA-2004-19203; the directorate identifier for this docket is 2004-NM-109-AD.                     

# FOR FURTHER INFORMATION CONTACT:

*Technical information:*                         Binh Tran, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 917-6485; fax (425) 917-6590.                     

*Plain language information:*                         Marcia Walters,                         *marcia.walters@faa.gov.*

# SUPPLEMENTARY INFORMATION:

## Docket Management System (DMS) 

The FAA has implemented new procedures for maintaining AD dockets electronically. As of May 17, 2004, new AD actions are posted on DMS and assigned a docket number. We track each action and assign a corresponding directorate identifier. The DMS AD docket number is in the form “Docket No. FAA-2004-99999.” The Transport Airplane Directorate identifier is in the form “Directorate Identifier 2004-NM-999-AD.” Each DMS AD docket also lists the directorate identifier (“Old Docket Number”) as a cross-reference for searching purposes. 

## Comments Invited 

                    We invite you to submit any written relevant data, views, or arguments regarding this proposed AD. Send your comments to an address listed under                     **ADDRESSES.**                     Include “Docket No. FAA-2004-19203; Directorate Identifier 2004-NM-109-AD” in the subject line of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. We will consider all comments submitted by the closing date and may amend the proposed AD in light of those comments.                 

                    We will post all comments we receive, without change, to                     *http://dms.dot.gov,*                     including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this proposed AD. Using the search function of that Web site, anyone can find and read the comments in any of our dockets, including the name of the individual                           ( print page 58110)                        who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You can review DOT's complete Privacy Act Statement in the                     **Federal Register**                     published on April 11, 2000 (65 FR 19477-78), or you can visit                     *http://dms.dot.gov.*

                    We are reviewing the writing style we currently use in regulatory documents. We are interested in your comments on whether the style of this document is clear, and your suggestions to improve the clarity of our communications that affect you. You can get more information about plain language at                     *http://www.faa.gov/​language*                     and                     *http://www.plainlanguage.gov.*

## Examining the Docket 

                    You can examine the AD docket on the Internet at                     *http://dms.dot.gov*, or in person at the Docket Management Facility office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Management Facility office (telephone (800) 647-5227) is located on the plaza level of the Nassif Building at the DOT street address stated in the                     **ADDRESSES**                     section. Comments will be available in the AD docket shortly after the DMS receives them.                 

## Discussion 

During a certification review of a Boeing Model 737-700C series airplane, a frequency converter failure mode that was not identified in the original system design was found. This failure mode could cause a wiring short circuit between the frequency converter output and the distribution circuit breakers. The current is only limited by the maximum current capacity of the frequency converter. The frequency converter reacts to a short circuit condition by increasing the output current to approximately 54 amps, and significantly reducing the voltage. Investigation revealed that the wiring between the converter and the wiring fault was inadequate in size to handle the frequency converters increased output current. These conditions, if not corrected, could result in a short circuit between the frequency converter output and the distribution circuit breakers, which could result in overheating and failure of adjacent wiring and consequent degraded operation of airplane systems. 

The frequency converters on certain Model 757-200 series airplanes are identical to those on the affected Model 737-700C series airplane (the unsafe condition has been corrected on Model 737-700C series airplanes). Therefore, all of these models may be subject to the same unsafe condition. 

## Relevant Service Information 

We have reviewed Boeing Service Bulletin 757-25-0255, dated December 11, 2003. The service bulletin describes procedures for modifying the frequency converters located in the closet assembly in the passenger compartment. The modification involves installing new, improved frequency converters, relay assemblies, thermal switches, and related components, and making various wiring changes in and between the closet assembly and forward purser work station. 

Affected airplanes are separated into Groups 1 and 2, and the Accomplishment Instructions of the service bulletin provide modification procedures for each group, as follows: The procedures for Groups 1 and 2 include replacing three frequency converters in closet assembly S3 in the passenger compartment; installing three relay assemblies; and changing wire bundles in the P37 panel and forward purser work station, including at and above closet assembly S3. Additional procedures for Group 2 include changing wire bundle W3910 in the ceiling between closet assembly S3 and the forward purser work station. The procedures for Groups 1 and 2 also specify doing an operational test of the new/changed frequency converters and related circuit changes. 

Service Bulletin 757-25-0255 recommends prior or concurrent accomplishment of Boeing Service Bulletin 757-24-0093, dated August 14, 2003. Service Bulletin 757-24-0093 describes procedures for modifying the in-flight entertainment system (circuit breaker, relays, and wiring). The modification procedures include installing a relay and changing the wiring in the main electronics compartment at the P37 panel assembly; and installing a relay and changing the wiring in the P36 panel assembly. The procedures also specify doing a continuity test. The modification procedures are for airplanes listed in Group 1 of Service Bulletin 757-24-0093. 

Accomplishing the actions specified in the service information is intended to adequately address the unsafe condition. 

## FAA's Determination and Requirements of the Proposed AD 

We have evaluated all pertinent information and identified an unsafe condition that is likely to exist or develop on other airplanes of this same type design. Therefore, we are proposing this AD, which would require modifying the frequency converters located in the closet assembly in the passenger compartment, and making various wiring changes in and between the closet assembly and forward purser work station. This proposed AD also would require accomplishment of various other actions prior to or concurrently with the modification of the frequency converters. The proposed AD would require you to use the service information described previously to perform these actions. 

## Costs of Compliance 

This proposed AD would affect about 4 airplanes of U.S. registry and 4 airplanes worldwide. 

For airplanes listed in Group 1 of Service Bulletin 757-25-0255: The proposed modification would take about 97 work hours (including access, close-up, and test), at an average labor rate of $65 per work hour. Required parts would cost about $10,710 per airplane. Based on these figures, the estimated cost of the proposed modification for U.S. operators is $17,015 per airplane. 

For airplanes listed in Group 2 of Service Bulletin 757-25-0255: The proposed modification would take about 105 work hours (including access, close-up, and test), at an average labor rate of $65 per work hour. Required parts would cost about $10,956 per airplane. Based on these figures, the estimated cost of the proposed modification for U.S. operators is $17,781 per airplane. 

For airplanes listed in Group 1 of Service Bulletin 757-24-0093: The proposed concurrent modification, if not previously done, would take about 49 work hours, at an average labor rate of $65 per work hour. Required parts would cost about $5,315 per airplane. Based on these figures, the estimated cost of the proposed modification for U.S. operators is $8,500 per airplane. 

## Regulatory Findings 

We have determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD 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. 

For the reasons discussed above, I certify that the 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                           ( print page 58111)    

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. 

                    We prepared a regulatory evaluation of the estimated costs to comply with this proposed AD. See the                     **ADDRESSES**                     section for a location to examine the regulatory evaluation.                 

# List of Subjects in 14 CFR Part 39

      - Air transportation
      - Aircraft
      - Aviation safety
      - Safety

## The Proposed Amendment 

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 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. The FAA amends § 39.13 by adding the following new airworthiness directive (AD): 

**Boeing:**                                 Docket No. FAA-2004-19203; Directorate Identifier 2004-NM-109-AD.                             

## Comments Due Date 

(a) The Federal Aviation Administration (FAA) must receive comments on this AD action by November 15, 2004. 

## Affected ADs 

(b) None. 

## Applicability 

(c) This AD applies to Model 757-200 series airplanes, certificated in any category, as listed in Boeing Service Bulletin 757-25-0255, dated December 11, 2003. 

## Unsafe Condition 

(d) This AD was prompted by a certification review that revealed a frequency converter failure mode not identified in the original system design. We are issuing this AD to prevent a short circuit between the frequency converter output and the distribution circuit breakers, which could result in overheating and failure of adjacent wiring and consequent degraded operation of airplane systems. 

## Compliance 

(e) You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done. 

## Modification 

(f) For all airplanes: Within 18 months after the effective date of this AD: Modify the frequency converters located in the closet assembly in the passenger compartment by doing all the applicable actions in accordance with the Accomplishment Instructions of Boeing Service Bulletin 757-25-0255, dated December 11, 2003. 

## Prior or Concurrent Modification 

(g) For Group 1 airplanes listed in Boeing Service Bulletin 757-24-0093, dated August 14, 2003: Before or concurrent with accomplishment of paragraph (f) of this AD, Modify the in-flight entertainment system by doing all the applicable actions in accordance with Boeing Service Bulletin 757-24-0093, dated August 14, 2003. 

## Part Installation 

(h) As of the effective date of this AD, no person may install a frequency converter having part number 1-002-0102-0730 on any airplane unless it has been modified as required by paragraph (f) of this AD. 

## Alternative Methods of Compliance (AMOCs) 

(i) The Manager, Seattle Aircraft Certification Office, FAA, has the authority to approve AMOCs for this AD, if requested in accordance with the procedures found in 14 CFR 39.19. 

Issued in Renton, Washington, on September 21, 2004. 

Kalene C. Yanamura, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 04-21818 Filed 9-28-04; 8:45 am] 

BILLING CODE 4910-13-P