06-2958. Airworthiness Directives; Boeing Model 737-600, -700, -700C, -800, and -900 Series Airplanes

AGENCY:

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

ACTION:

Final rule.

SUMMARY:

The FAA is adopting a new airworthiness directive (AD) for certain Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes. This AD requires 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 terminates the repetitive general visual inspections. This AD results from 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.

DATES:

This AD becomes effective May 4, 2006.

The Director of the Federal Register approved the incorporation by reference of certain publications listed in the AD as of May 4, 2006.

ADDRESSES:

You may examine the AD docket on the Internet at http://dms.dot.gov or in person at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street, SW., Nassif Building, room PL-401, Washington, DC.

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

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 [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Examining the Docket

You may examine the airworthiness directive (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 [phone]) is located on the plaza level of the Nassif Building at the street address stated in the ADDRESSES section.

Discussion

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an AD that would apply to certain Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes. That NPRM was published in the Federal Register on January 24, 2005 (70 FR 3320). That NPRM proposed to 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.

Comments

We provided the public the opportunity to participate in the development of this AD. We have considered the comments received.

Support for NPRM

Southwest Airlines and AirTran Airways support the NPRM.

Request To Revise Dimension Between Certain Fastener Holes

Alaska Airlines requests that we revise the dimension between certain fastener holes specified in Figures 3, 4, 5, and 6 of Boeing Special Attention Service Bulletin 737-54-1041, dated January 22, 2004. Alaska Airlines states that the dimension between an existing fastener hole and the new fastener hole is called out in the ten-thousandths (1.6772 inches); any deviation from this exact measurement would require approval of an alternative method of compliance (AMOC). Alaska Airlines suggests dimensions of 1.67 or 1.68 inches with a standard tolerance of ±0.03 inch. If we cannot revise the dimension, the commenter instead requests that we clarify why such a tight tolerance would be required.

We agree with Alaska Airlines' request, since there is no technical justification for requiring such a tight tolerance between fastener holes. Since issuance of the NPRM, Boeing has published Service Bulletin 737-54-1041, Revision 1, dated December 1, 2005. The procedures in Revision 1 of the service bulletin are essentially the same as those in the original issue, dated January 22, 2004, which we referenced in the NPRM as the appropriate source of service information. Revision 1 allows a dimension of 1.647 inches to 1.707 inches between fastener holes. Therefore, we have revised this AD to also allow use of Revision 1 for accomplishing the actions specified in this AD. We have also revised paragraph (c) of this AD to reference Revision 1. Since the effectivity of Revision 1 is the same as the effectivity of the original issue, the applicability of this AD has not changed.

Clarification of AMOC Paragraph

We have revised this action to clarify the appropriate procedure for notifying the principal inspector before using any approved AMOC on any airplane to which the AMOC applies.

Conclusion

We have carefully reviewed the available data, including the comments received, and determined that air safety and the public interest require adopting the AD with the changes described previously. We have determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.

Costs of Compliance

This AD affects about 1,406 airplanes worldwide and about 549 U.S.-registered airplanes. The following table provides the estimated costs for U.S. operators to comply with this AD.

Estimated Costs

Action	Work hours	Average labor rate per hour	Parts	Cost per airplane	Number of U.S.- registered airplanes	Fleet cost
Inspection, per inspection cycle	2	$65	None	$130, per inspection cycle	549	$71,370, per inspection cycle.
Modification	5	65	$294	$619	549	$339,831.

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 AD will not have federalism implications under Executive Order 13132. This AD will 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 this AD:

(1) Is not a “significant regulatory action” under Executive Order 12866;

(2) Is not a “significant rule” under 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 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
• Incorporation by reference
• Safety

Adoption of the Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 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

[Amended]

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

2006-07-04 Boeing: Amendment 39-14531. Docket No. FAA-2005-20110; Directorate Identifier 2004-NM-114-AD.

Effective Date

(a) This AD becomes effective May 4, 2006.

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 Service Bulletin 737-54-1041, Revision 1, dated December 1, 2005.

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; or Boeing Service Bulletin 737-54-1041, Revision 1, dated December 1, 2005.

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)(1) 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.

(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.

Material Incorporated by Reference

(k) You must use Boeing Special Attention Service Bulletin 737-54-1041, dated January 22, 2004; or Boeing Service Bulletin 737-54-1041, Revision 1, dated December 1, 2005, to perform the actions that are required by this AD, unless the AD specifies otherwise. The Director of the Federal Register approved the incorporation by reference of these documents in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207, for a copy of this service information. You may review copies at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street, SW., room PL-401, Nassif Building, Washington, DC; on the Internet at http://dms.dot.gov; or at the National Archives and Records Administration (NARA). For information on the availability of this material at the NARA, call [phone], or go to http://www.archives.gov/​federal_​register/​code_​of_​federal_​regulations/​ibr_​locations.html.

Issued in Renton, Washington, on March 17, 2006.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.