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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. FAA-2005-22874; Directorate Identifier 2005-NM-173-AD] 
          - RIN 2120-AA64 

# AGENCY:

Federal Aviation Administration (FAA), Department of Transportation (DOT). 

# ACTION:

Notice of proposed rulemaking (NPRM). 

# SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 777-200 and -300 series airplanes. This proposed AD would require inspecting the lower web of the aft fairing of engine struts for any discoloration and doing any related investigative and corrective action if necessary; inspecting the heat shield castings for any damage and doing any corrective action if necessary; installing gap cover strips; and replacing insulation blankets with new insulation blankets. This proposed AD results from a report that several discolored fairing lower webs and some damaged/deteriorated insulation blankets were found in the aft fairings of engine struts. We are proposing this AD to prevent cracking of lower webs of the aft fairings, which could result in flammable hydraulic fluid leaking onto or near an ignition source, and possibly result in an uncontrollable fire in the engine strut area. 

# DATES:

We must receive comments on this proposed AD by December 27, 2005. 

# 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.
      - 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.

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

# FOR FURTHER INFORMATION CONTACT:

John Vann, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 917-6513; fax (425) 917-6590. 

# SUPPLEMENTARY INFORMATION:

## Comments Invited 

                    We invite you to submit any relevant written data, views, or arguments regarding this proposed AD. Send your comments to an address listed in the                     **ADDRESSES**                     section. Include the docket number “FAA-2005-22874; Directorate Identifier 2005-NM-173-AD” at the beginning 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 received 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 who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You may review DOT's complete Privacy Act Statement in the                     **Federal Register**                     published on April 11, 2000 (65 FR 19477-78), or you may visit                     *http://dms.dot.gov.*

## Examining the Docket 

                    You may 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 Docket Management System receives them.                 

## Discussion 

                    We have received a report indicating that damaged/deteriorated thermal insulation blankets and discolored fairing lower webs were found in the aft fairings of engine struts on several Model 777-200 and -300 series airplanes. Gaps in the segmented heat shield in the strut aft fairings allow engine primary/main exhaust to enter the heat shield cavity in the strut aft fairing. The temperature of the exhaust that leaks into the heat shield cavity exceeds the insulation blankets' maximum design tolerance. Since the insulation blankets provide thermal protection for the aluminum fairing lower web, degradation of an insulation blanket allows thermal distress of the lower web and eventually, cracking of the lower web. A cracked lower web is                           ( print page 67953)                        also a possible leak path for hydraulic fluid to come into direct contact with the heat shield, the temperature of which can exceed the hydraulic fluid's auto-ignition temperature (750 degrees Fahrenheit). Gaps in the heat shield, if not corrected, could result in cracked fairing lower webs and consequently leak flammable hydraulic fluid onto or near an ignition source and possibly result in an uncontrollable fire in the engine strut area.                 

## Relevant Service Information 

We have reviewed Boeing Special Attention Service Bulletin 777-54-0021, dated June 23, 2005. The service bulletin describes the following procedures: 
    - Doing a general visual inspection of the lower web of the aft fairing for any discoloration and doing any related investigative and corrective action if necessary;
    - Doing a general visual inspection of the heat shield castings for any damage (crack(s), dent(s), gouge(s), warpage, or fretting) and doing any corrective action if necessary;
    - Installing gap cover strips; and
    - Replacing insulation blankets with new blankets.

The related investigative action is a special detailed inspection for heat damage and for cracks at the fastener holes of areas with discolored paint or primer. The corrective action is to contact Boeing for repair instructions if any damage is found during the inspections. 

The corrective action for any damage found during an inspection of the heat shield castings involves contacting Boeing for instructions on repairing or replacing damaged heat shields before further flight. 

Replacing the insulation blankets with new insulation blankets may involve modifying the configuration of the insulation blanket velcro strips into a new configuration if the strips were previously installed in a particular configuration before 1997. 

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. For this reason, we are proposing this AD, which would require accomplishing the actions specified in the service information described previously, except as discussed under “Difference Between the Proposed AD and the Service Bulletin.” 

## Difference Between the Proposed AD and the Service Bulletin 

The service bulletin specifies that you may contact the manufacturer for instructions on how to repair certain conditions, but this proposed AD would require you to repair those conditions in one of the following ways: 
    - Using a method that we approve; or
    - Using data that meet the certification basis of the airplane, and that have been approved by an Authorized Representative for the Boeing Commercial Airplanes Delegation Option Authorization Organization who has been authorized by the FAA to make those findings.

## Costs of Compliance 

There are about 294 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 72 airplanes of U.S. registry. The proposed actions would take about 9 to 11 work hours per airplane, depending on engine manufacturer (configuration), at an average labor rate of $65 per work hour. Required parts would cost about $15,368 to $16,179 per airplane. Based on these figures, the estimated cost of the proposed AD for U.S. operators is $1,148,616 to $1,216,368, or $15,953 to $16,894 per airplane. 

## Authority for This Rulemaking 

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority. 

We are issuing this rulemaking under the authority described in subtitle VII, part A, subpart III, section 44701, “General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action. 

## 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 

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 and placed it in the AD docket. 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 Federal Aviation Administration (FAA) amends § 39.13 by adding the following new airworthiness directive (AD):

**Boeing:**                                 Docket No. FAA-2005-22874; Directorate Identifier 2005-NM-173-AD.                             

## Comments Due Date 

(a) The FAA must receive comments on this AD action by December 27, 2005. 

## Affected ADs 

(b) None. 

## Applicability 

(c) This AD applies to Boeing Model 777-200 and -300 series airplanes, certificated in any category; as identified in Boeing Special Attention Service Bulletin 777-54-0021, dated June 23, 2005. 

## Unsafe Condition 

                                (d) This AD results from a report that several discolored fairing lower webs and some damaged/deteriorated insulation blankets were found in the aft fairings of engine struts. We are issuing this AD to prevent cracking of lower webs of the aft fairings, which could result in flammable hydraulic fluid leaking onto or near an ignition source, and possibly result in an uncontrollable fire in the engine strut area.                                       ( print page 67954)    

## 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. 

## Inspection, Installation, and Replacement Actions 

(f) Except as provided by paragraph (g) of this AD: Within 12 months after the effective date of this AD, do the actions specified in paragraphs (f)(1), (f)(2), (f)(3), and (f)(4) in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 777-54-0021, dated June 23, 2005. Do any corrective or related investigative action before further flight in accordance with the service bulletin. 

(1) Do a general visual inspection of the lower web of the aft fairing for any discoloration and do any applicable related investigative and corrective action. 

(2) Do a general visual inspection of the heat shield castings for any damage (crack(s), dent(s), gouge(s), warpage, or fretting) and do any applicable corrective action. 

(3) Install gap cover strips on the heat shield pans. 

(4) Replace insulation blankets on the heat shield pans with new insulation blankets. 

## Repair Instructions 

(g) If any damage, discoloration, heat damage, or crack(s) is found during any inspection required by this AD, and Boeing Special Attention Service Bulletin 777-54-0021, dated June 23, 2005, specifies contacting Boeing for appropriate action: Before further flight, repair the damage using a method approved in accordance with the procedures specified in paragraph (h) of this AD. 

## Alternative Methods of Compliance (AMOCs) 

(h)(1) The Manager, Seattle Aircraft Certification Office (ACO), FAA, has the authority to approve AMOCs for this AD, if requested in accordance with the procedures found in 14 CFR 39.19. 

(2) Before using any AMOC approved in accordance with 14 CFR 39.19 on any airplane to which the AMOC applies, notify the appropriate principal inspector in the FAA Flight Standards Certificate Holding District Office. 

(3) An AMOC that provides an acceptable level of safety may be used for any repair required by this AD, if it is approved by an Authorized Representative for the Boeing Commercial Airplanes Delegation Option Authorization Organization who has been authorized by the Manager, Seattle ACO, to make those findings. For a repair method to be approved, the repair must meet the certification basis of the airplane, and the approval must specifically refer to this AD.

Issued in Renton, Washington, on October 26, 2005. 

Kalene C. Yanamura, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 05-22306 Filed 11-8-05; 8:45 am] 

BILLING CODE 4910-13-P