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Proposed Rule

Airworthiness Directives; Boeing Model 737-600, -700, -700C, -800, and -900 Series Airplanes

Document Details

Information about this document as published in the Federal Register.

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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 737-600, -700, -700C, -800, and -900 series airplanes. This proposed AD would require repetitive general visual inspections for dirt, debris, and drain blockage and cleaning of the aft fairing cavities of the engine struts; and modification of the aft fairings, which would terminate the repetitive general visual inspections. This proposed AD is prompted by a report indicating that water had accumulated in the cavities of the engine strut aft fairings. We are proposing this AD to prevent drain blockage by debris that, when combined with leaking, flammable fluid lines passing through the engine strut aft fairing, could allow flammable fluids to build up in the cavity of the aft fairing, and consequently could be ignited by the engine exhaust nozzle located below the engine strut, resulting in an explosion or uncontrolled fire.

DATES:

We must receive comments on this proposed AD by March 10, 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.
  • 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-2005-20110; the directorate identifier for this docket is 2004-NM-114-AD.

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FOR FURTHER INFORMATION CONTACT:

Doug Pegors, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 917-6504; fax (425) 917-6590.

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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 under ADDRESSES. Include “Docket No. FAA-2005-20110; Directorate Identifier 2004-NM-114-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 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.

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 Start Printed Page 3321section. Comments will be available in the AD docket shortly after the DMS receives them.

Discussion

We have received a report indicating that water had accumulated in the cavities of the engine strut aft fairings on several Boeing Model 737-700 series airplanes. Build up of debris in the sump area of the cavity of the aft fairing had blocked the drain, which caused approximately 12 inches of water to accumulate. Debris and water had entered through gaps between the engine strut fairing and the thrust reverser skirt fairing at the wing interface blade seal. A drain blocked by debris in combination with flammable fluid lines, which pass through the engine strut aft fairing and occasionally leak, could cause a hazardous amount of flammable fluid to build up in the cavity of the aft fairing. This condition, if not corrected, could result in the ignition of the flammable fluid by the exhaust nozzle located below the engine strut and consequent explosion or uncontrolled fire.

The aft fairing of the engine strut on certain Boeing Model 737-600, -700C, -800, and -900 series airplanes are identical to those on the affected Model 737-700 series airplanes. Therefore, all of these models may be subject to the same unsafe condition.

Relevant Service Information

We have reviewed Boeing Special Attention Service Bulletin 737-54-1041, dated January 22, 2004. The service bulletin describes procedures for repetitive general visual inspections for dirt, debris, and drain blockage and cleaning of the aft fairing cavities of the left and right engine struts; and modification of the aft fairings of the left and right engine struts, which eliminates the need for repetitive general visual inspections. Modification involves installing new, improved seals on the inboard and outboard sides of the aft fairings of the left and right engine struts. 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 repetitive general visual inspections for dirt, debris, and drain blockage and cleaning of the aft fairing cavities of the left and right engine struts; and modification of the aft fairings of the left and right engine struts, which would terminate the repetitive general visual inspections. Modification involves installing new, improved seals on the inboard and outboard sides of the aft fairings of the left and right engine struts. The proposed AD would require you to use the service information described previously to perform these actions, except as discussed under “Differences Between the Proposed AD and Service Bulletin.”

Differences Between Proposed AD and Service Bulletin

Boeing Special Attention Service Bulletin 737-54-1041, dated January 22, 2004, specifies that operators may accomplish the general visual inspection and cleaning of the aft fairing cavities in accordance with either the Boeing 737-600/700/800/900 Airplane Maintenance Manual (AMM) or an “approved equivalent procedure.” However, this proposed AD would require operators to accomplish the actions in accordance with the procedures specified in Chapter 54-55-02 of the Boeing 737-600/700/800/900 AMM. An “approved equivalent procedure” may be used only if approved as an alternative method of compliance in accordance with paragraph (j) of this AD.

The proposed AD would require inspecting and cleaning the drain system of an aft fairing after the modifications required by paragraph (i) of this AD. We have determined that modification alone would not eliminate the build up of debris and flammable fluids in the cavity of the aft fairing since the most previous inspection. Therefore, operators must inspect and clean the aft fairings when the modification is done.

Costs of Compliance

This proposed AD would affect about 1,406 airplanes worldwide. The following table provides the estimated costs for U.S. operators to comply with this proposed AD.

Estimated Costs

ActionWork hoursAverage labor rate per hourPartsCost per airplaneNumber of U.S.- registered airplanesFleet cost
Inspection, per inspection cycle2$65None$130, per inspection cycle549$71,370, per inspection cycle.
Modification565$294619549339,831.

Authority for This Rulemaking

The FAA's authority to issue rules regarding aviation safety is found in Title 49 of the United States Code. 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.

This rulemaking is promulgated 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 AD.

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, Start Printed Page 3322on 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.

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List of Subjects in 14 CFR Part 39

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The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

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PART 39—AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

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Authority: 49 U.S.C. 106(g), 40113, 44701.

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[Amended]

2. The FAA amends § 39.13 by adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2005-20110; Directorate Identifier 2004-NM-114-AD.

Comments Due Date

(a) The Federal Aviation Administration (FAA) must receive comments on this AD action by March 10, 2005.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes, certificated in any category; as listed in Boeing Special Attention Service Bulletin 737-54-1041, dated January 22, 2004.

Unsafe Condition

(d) This AD was prompted by a report indicating that water had accumulated in the cavities of the engine strut aft fairings. We are issuing this AD to prevent drain blockage by debris that, when combined with leaking, flammable fluid lines passing through the engine strut aft fairing, could allow flammable fluids to build up in the cavity of the aft fairing, and consequently could be ignited by the engine exhaust nozzle located below the engine strut, resulting in an explosion or uncontrolled fire.

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.

Service Bulletin Reference

(f) The term “service bulletin,” as used in this AD, means the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-54-1041, dated January 22, 2004.

Repetitive Inspections of the Engine Strut Aft Fairings

(g) Within 4,000 flight cycles or within 30 months after the effective date of this AD, whichever occurs first: Do the actions specified in paragraphs (g)(1) and (g)(2) of this AD.

(1) Do a general visual inspection for dirt, debris, and drain blockage and clean the aft fairing cavity of the left engine strut, in accordance with Part I of the service bulletin, except as provided by paragraph (h) of this AD. Thereafter at intervals not to exceed 4,000 flight cycles or 30 months, whichever occurs first: Repeat the inspection until the aft fairing of the left engine strut has been modified in accordance with paragraph (i)(1) of this AD.

(2) Do a general visual inspection for dirt, debris, and drain blockage and clean the aft fairing cavity of the right engine strut, in accordance with Part II of the service bulletin, except as provided by paragraph (h) of this AD. Thereafter at intervals not to exceed 4,000 flight cycles or 30 months, whichever occurs first: Repeat the inspection until the aft fairing of the right engine strut has been modified in accordance with paragraph (i)(2) of this AD.

Note 1:

For the purposes of this AD, a general visual inspection is: “A visual examination of an interior or exterior area, installation, or assembly to detect obvious damage, failure, or irregularity. This level of inspection is made from within touching distance unless otherwise specified. A mirror may be necessary to ensure visual access to all surfaces in the inspection area. This level of inspection is made under normally available lighting conditions such as daylight, hangar lighting, flashlight, or droplight and may require removal or opening of access panels or doors. Stands, ladders, or platforms may be required to gain proximity to the area being checked.”

Approved Equivalent Procedure

(h) If the service bulletin specifies that the general visual inspection and cleaning of the aft fairing cavity of the left or right engine strut may be accomplished per an “approved equivalent procedure”: The general visual inspection or cleaning must be accomplished in accordance with the chapter of the Boeing 737-600/700/800/900 Airplane Maintenance Manual specified in the service bulletin.

Modification of the Engine Strut Aft Fairings

(i) Within 9,000 flight cycles after the effective date of this AD, do the actions specified in paragraphs (i)(1) and (i)(2) of this AD.

(1) Modify the aft fairing of the left engine strut, in accordance with Part III of the service bulletin; and after accomplishing the modification but before further flight, inspect and clean the drain system of the aft fairing in accordance with Part I of the service bulletin. This modification terminates the repetitive inspections required by paragraph (g)(1) of this AD.

(2) Modify the aft fairing of the right engine strut, in accordance with Part IV of the service bulletin; and after accomplishing the modification but before further flight, inspect and clean the drain system of the aft fairing in accordance with Part II of the service bulletin. This modification terminates the repetitive inspections required by paragraph (g)(2) of this AD.

Alternative Methods of Compliance (AMOCs)

(j) 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.

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Issued in Renton, Washington, on January 12, 2005.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.

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[FR Doc. 05-1220 Filed 1-21-05; 8:45 am]

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