E7-22548. Airworthiness Directives; Boeing Model 737-600, 737-700, 737-700C, 737-800, and 737-900 Series Airplanes

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, 737-700, 737-700C, 737-800, and 737-900 series airplanes. This proposed AD would require an inspection of the vertical fin lugs, skin, and skin edges for discrepancies, an inspection of the flight control cables, fittings, and pulleys in section 48 for signs of corrosion, an inspection of the horizontal stabilizer jackscrew, ball nut, and gimbal pins for signs of corrosion, and corrective actions if necessary. This proposed AD results from reports indicating that moisture was found within the section 48 cavity. We are proposing this AD to ensure that the correct amount of sealant was applied around the vertical fin lugs, skin and the skin edges. Missing sealant could result in icing of the elevator cables, which could cause a system jam and corrosion of structural and flight control parts, resulting in reduced controllability of the airplane.

DATES:

We must receive comments on this proposed AD by January 3, 2008.

ADDRESSES:

You may send comments by any of the following methods:

• Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
• Fax: [phone].
• Mail: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.
• Hand Delivery: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

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

Examining the AD Docket

You may examine the AD docket on the Internet at http://www.regulations.gov; or in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this proposed AD, the regulatory evaluation, any comments received, and other information. The street address for the Docket Office (telephone [phone]) is in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT:

Wayne Lockett, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to send any written relevant data, views, or arguments about this proposed AD. Send your comments to an address listed under the ADDRESSES section. Include “Docket No. FAA-2007-0202; Directorate Identifier 2007-NM-185-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this proposed AD. We will consider all comments received by the closing date and may amend this proposed AD because of those comments.

We will post all comments we receive, without change, to http://www.regulations.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact we receive about this proposed AD.

Discussion

We have received reports indicating that moisture was found within the section 48 cavity on Boeing Model 737-600, 737-700, 737-700C, 737-800, and 737-900 series airplanes. A root-cause investigation determined that, due to a manufacturing process error, airplanes were delivered with an incorrect amount of sealant around the station (STA) 1088 vertical fin lugs common to the section 48 skin. This condition, if not corrected, could result in icing of the elevator cables, which could cause a system jam and corrosion of structural and flight control parts, resulting in reduced controllability of the airplane.

Relevant Service Information

We have reviewed Boeing Service Bulletin 737-53A1242, Revision 2, dated April 23, 2007. The service bulletin describes the following procedures:

• Inspecting the vertical fin lugs, skin, and skin edges for discrepancies (i.e. water ingress, corrosion damage, and missing, insufficient, or cracked sealant).
• Performing a detailed inspection of the flight control cables, fittings, and pulleys in section 48 for signs of corrosion.
• Performing a detailed inspection of the horizontal stabilizer jackscrew, ball nut, and gimbal pins for signs of corrosion.
• Performing applicable corrective actions. The corrective actions include repairing cracks, filling the space between the vertical fin lugs and skin, lubricating the horizontal stabilizer trim actuator and actuator gimbal pins, replacing any cracked sealant with a new sealant, and contacting Boeing for corrosion repair conditions, as applicable.

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 Service Bulletin.”

Difference Between the Proposed AD and Service Bulletin

In this proposed AD, the “inspection” and “visual inspection” specified in the Boeing service bulletin is referred to as a “detailed inspection.” We have included the definition for a detailed inspection in a note in the proposed AD.

The service bulletin specifies to contact the manufacturer for instructions on how to repair certain conditions, but this proposed AD would require repairing 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 whom we have authorized to make those findings.

Costs of Compliance

There are about 829 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 372 airplanes of U.S. registry. The proposed actions would take about 1 work hour per airplane, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the proposed AD for U.S. operators is $29,760, or $80 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

[Amended]

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

Boeing: Docket No. FAA-2007-0202; Directorate Identifier 2007-NM-185-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by January 3, 2008.

Affected ADs

(b) None.

Applicability

(c) This AD applies to certain Boeing Model 737-600, 737-700, 737-700C, 737-800, and 737-900 series airplanes, certificated in any category; as identified in Boeing Service Bulletin 737-53A1242, Revision 2, dated April 23, 2007.

Unsafe Condition

(d) This AD results from reports indicating that moisture was found within the section 48 cavity. We are issuing this AD to ensure that the correct amount of sealant was applied around the vertical fin lugs, skin and the skin edges. Missing sealant could result in icing of the elevator cables, which could cause a system jam and corrosion of structural and flight control parts, resulting in reduced controllability of the airplane.

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.

Inspections

(f) Within 2,500 flight cycles or 18 months after the effective date of this AD, whichever occurs first, do the detailed inspections specified in paragraphs (f)(1), (f)(2) and (f)(3) of this AD in accordance with the Accomplishment Instructions of the Boeing Service Bulletin 737-53A1242, Revision 2, dated April 23, 2007.

(1) Do a detailed inspection of the vertical fin lugs, skin, and skin edges for discrepancies (i.e. water ingress, corrosion damage, and missing, insufficient, or cracked sealant).

(2) Do a detailed inspection of the flight control cables, fittings, and pulleys in section 48 for signs of corrosion.

(3) Do a detailed inspection of the horizontal stabilizer jackscrew, ball nut, and gimbal pins for signs of corrosion.

Note 1:

For the purposes of this AD, a detailed inspection is: “An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector (i.e., the person performing the inspection). Inspection aids such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required.”

Corrective Actions

(g) If any discrepancy or corrosion is found during any inspection required by paragraph (f) of this AD, before further flight, do the applicable corrective actions in accordance with the Accomplishment Instructions of Boeing Service Bulletin 737-53A1242, Revision 2, dated April 23, 2007; except where the service bulletin specifies to contact Boeing, repair using a method approved in accordance with the procedures specified in paragraph (i) of this AD.

Credit for Actions Done Using the Previous Service Information

(h) Actions accomplished before the effective date of this AD in accordance with Boeing Service Bulletin 737-53A1242, dated October 17, 2002; and Revision 1, dated April 28, 2005; are considered acceptable for compliance with the corresponding actions specified in paragraphs (f) and (g) of this AD.

Alternative Methods of Compliance (AMOCs)

(i)(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) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Before using any approved AMOC on any airplane to which the AMOC applies, notify your appropriate principal inspector (PI) in the FAA Flight Standards District Office (FSDO), or lacking a PI, your local FSDO.

(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 November 7, 2007.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.