E9-24986. Airworthiness Directives; Boeing Model 737-600, -700, -700C, -800, and -900 Series Airplanes

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

We propose 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 inspections for scribe lines in the fuselage skin at lap joints, the splice strap at certain butt joints, the skin or doubler at certain approved repair doublers, and the skin at decal locations; and related investigative and corrective actions if necessary. This proposed AD results from reports of scribe line damage found adjacent to the skin lap joints, decals, and wing-to-body fairings. We are proposing this AD to detect and correct scribe lines, which can develop into fatigue cracks in the skin. Undetected fatigue cracks can grow and cause sudden decompression of the airplane.

DATES:

We must receive comments on this proposed AD by December 3, 2009.

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 proposed AD, contact Boeing Commercial Airplanes, Attention: Data & Services Management, P.O. Box 3707, MC 2H-65, Seattle, Washington 98124-2207; telephone [phone], extension 1; fax [phone]; e-mail [e-mail]; Internet https://www.myboeingfleet.com. You may review copies of the referenced service information at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington. For information on the availability of this material at the FAA, call 425-227-1221 or 425-227-1152.

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-2009-0913; Directorate Identifier 2009-NM-101-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 scribe lines have been found by multiple operators on Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes. The scribe lines appear to have been made on the skin when sealant was removed as part of preparing the airplane for repainting. One Model 737-700 operator reported scribe lines found around the wing-to-body fairing between stringer 26L and stringer 25R at station (STA) 727D to STA 727E. A second Model 737-700 operator reported six vertical scribe lines up to 42 inches long on the upper aft fuselage between stringer 5R and stringer 9R at STA 847 to STA 887. Another 737-700 operator reported scribe lines along stringer 24L and stringer 24R between STA 178 to STA 500B. The depth of the scribe lines ranged from 0.001 inch to 0.004 inch. The airplanes had accumulated between 595 and 17,571 total flight cycles. No cracks as a result of scribe lines found on Model 737-600, -700, -700C, -800, and -900 airplanes have been reported to Boeing.

Related ADs

This proposed AD is similar to two existing ADs. AD 2006-07-12, amendment 39-14539 (71 FR 16211, March 31, 2006), applies to Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. AD 2007-19-07, amendment 39-15198 (72 FR 60244, October 24, 2007), applies to Boeing Model 757-200, -200PF, and -200CB series airplanes. Those ADs require inspections to detect scribe lines in the fuselage skin at certain lap joints, butt joints, external repair doublers, and other areas; and related investigative/corrective actions if necessary. Those actions resulted from reports of fuselage skin cracks adjacent to the skin lap joints on airplanes that had scribe lines.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 737-53A1289, dated January 14, 2009. That service bulletin describes procedures for inspecting for scribe lines in the fuselage skin at lap joints, the splice strap at certain butt joints, the skin or doubler at certain approved repair doublers, and the skin at decal locations. That service bulletin specifies removing paint and sealant from affected areas before the initial inspection. The service bulletin specifies that the compliance time for the inspections ranges between before accumulating 14,000 total flight cycles plus the first scribe line opportunity, and 75,000 total flight cycles, depending on the inspection location, or within 4,000 flight cycles after the date the service bulletin was issued (whichever occurs later).

That service bulletin specifies related investigative and corrective actions. The related investigative actions include performing repetitive detailed, high frequency eddy current, ultrasonic, and/or ultrasonic phased array inspections of the scribe lines to detect cracks. The repetitive inspection interval ranges between 1,000 and 10,000 flight cycles, depending on the condition found. The corrective actions include repairing scribe lines and cracks. The service bulletin specifies to repair cracks before further flight.

That service bulletin also specifies repairing scribe lines before further flight, except when a limited return to service (LRTS) program for qualifying scribe lines would allow return to service for a limited period before scribe lines are repaired. The LRTS program includes repetitive inspections to detect cracks where scribe lines are found. To qualify for an LRTS program, scribe lines must meet certain criteria based on their depth and location. That service bulletin specifies final repair by using the structural repair manual or contacting Boeing for instructions, which would eliminate the need for the repetitive inspections of the LRTS program. The repetitive intervals for the LRTS program range from 2,500 flight cycles to 10,000 flight cycles after the scribe line is found, depending on the inspection location.

That service bulletin notes that certain inspections would not be necessary under the following conditions:

• The airplane has never been stripped or repainted, or the airplane was stripped or repainted after July 1, 2007.
• The airplane has never had decals installed, or decals were installed after July 1, 2007.
• For each repair, the airplane has never been stripped or repainted since the repair was installed or the repair was installed after July 1, 2007.
• The area under the wing-to-body fairings has never been stripped or repainted or the airplane was stripped or repainted after July 1, 2007.
• No sealant has been removed except in accordance with the specified sealant removal processes given in Appendix A of the service bulletin.

That service bulletin specifies submitting inspection results to Boeing. The service bulletin also provides procedures for addressing scribe lines detected before the initial inspection threshold.

FAA's Determination and Requirements of This Proposed AD

We are proposing this AD because we evaluated all relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the same type design. This proposed AD would require accomplishing the actions specified in the service information described previously, except as discussed under “Differences Between the Proposed AD and Service Bulletin.” The proposed AD would also require sending the inspection results to Boeing.

Differences Between the Proposed AD and Service Bulletin

Where the service bulletin specifies contacting the manufacturer for instructions on how to repair certain conditions, 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

We estimate that this proposed AD would affect 782 airplanes of U.S. registry. The following table provides the estimated costs for U.S. operators to comply with this proposed AD.

Table—Estimated Costs

Action	Work hours	Average labor rate per hour	Parts	Cost per product	Number of U.S.- registered airplanes	Fleet cost
Inspection	53	$80	$0	$4,240 per inspection cycle	782	$3,315,680 per inspection cycle.

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 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 this 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.

You can find our regulatory evaluation and the estimated costs of compliance in the AD Docket.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Incorporation by reference
• 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 FAA amends § 39.13 by adding the following new AD:

Boeing: Docket No. FAA-2009-0913; Directorate Identifier 2009-NM-101-AD.

Comments Due Date

(a) We must receive comments by December 3, 2009.

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 identified in Boeing Alert Service Bulletin 737-53A1289, dated January 14, 2009.

Subject

(d) Air Transport Association (ATA) of America Code 53: Fuselage.

Unsafe Condition

(e) This AD results from reports of scribe line damage found adjacent to the skin lap joints, decals, and wing-to-body fairings. The Federal Aviation Administration is issuing this AD to detect and correct scribe lines, which can develop into fatigue cracks in the skin. Undetected fatigue cracks can grow and cause sudden decompression of the airplane.

Compliance

(f) 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

(g) At the applicable times specified in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1289, dated January 14, 2009 (“the service bulletin”), except as provided in paragraph (h) of this AD, do detailed external inspections for scribe lines in the fuselage skin at lap joints, the splice strap at certain butt joints, the skin or doubler at certain approved repair doublers, and the skin at decals; and do all applicable related investigative and corrective actions, by accomplishing all actions specified in the Accomplishment Instructions of the service bulletin, except as provided by paragraph (i) of this AD.

Note 1:

The inspection exceptions described in subparagraphs 1.a. through 1.e. in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1289, dated January 14, 2009, apply to this AD.

Exceptions to Service Bulletin Specifications

(h) Where Boeing Alert Service Bulletin 737-53A1289, dated January 14, 2009, specifies a compliance time after the date on the service bulletin, this AD requires compliance within the specified compliance time after the effective date of this AD.

(i) Where Boeing Alert Service Bulletin 737-53A1289, dated January 14, 2009, specifies to contact Boeing for appropriate action, accomplish applicable actions using a method approved in accordance with the procedures specified in paragraph (k) of this AD.

Report

(j) At the applicable time specified in paragraph (j)(1) or (j)(2) of this AD: Submit a report of the findings (both positive and negative) of the inspections required by paragraph (g) of this AD. You may use Appendix B of Boeing Alert Service Bulletin 737-53A1289, dated January 14, 2009. Send the report to Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207. The report must contain, at a minimum, the inspection results, a description of any discrepancies found, the airplane serial number, and the number of flight cycles and flight hours on the airplane. Under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.), the Office of Management and Budget (OMB) has approved the information collection requirements contained in this AD and has assigned OMB Control Number 2120-0056.

(1) If the inspection was done on or after the effective date of this AD: Submit the report within 30 days after the inspection.

(2) If the inspection was done before the effective date of this AD: Submit the report within 30 days after the effective date of this AD.

Alternative Methods of Compliance (AMOCs)

(k)(1) The Manager, Seattle Aircraft Certification Office, FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. Send information to ATTN: 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]. Or, e-mail information to [e-mail].

(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 principal maintenance inspector (PMI) or principal avionics inspector (PAI), as appropriate, or lacking a principal inspector, your local Flight Standards District Office. The AMOC approval letter must specifically reference this AD.

(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 5, 2009.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.